Vol . 8 No . 1 (Jan – Mar 2014) A Quar ter ly Newsle t te r

WATERPROOFING

PART - 8

WATERPROOFING AND LOW ENERGY

CONSUMPTION ROOFING SYSTEMS

It has been observed that in an average building envelope 23% of the heat is transferred through the roof, which is the highest percentage when compared to walls, windows, etc. It is often a challenge while contemplating a change from the traditional black roof system to an energy efficient one, or determining the savings when considering alternatives for a new building or the retrofitting of an existing building. While considering the energy efficiency of waterproofing performances, the latest low energy consumption roofing system, popularly known as the LEC system, has gained momentum in various metros in India. Basically, the system consists of a mixture of multiple materials that are blended together. Though they bear different physical or chemical properties, when combined together they produce a system which is capable of delivering durable, energy-efficient, high-performance and sustainable roofing. However, the following criteria need to be considered for calculating the energy efficient performance of vegetative roofs/roof gardens/green roof systems or energy efficient roofs:

• Climate and geographical location

• Building’s intended use and design life expectancy

• Exterior and interior temperature, humidity and use conditions

• Type and condition of substrate

• Structural system

• Slope and drainage

• Roof waterproofing membrane

• Type of vegetative roof system including overburden, if any

• Type and amount of insulation, protection and drainage needed

• Type of reflecting material

As per the International Energy Conservation Code (IECC) 2012 and ASHRAE 90.1, “Energy standard for buildings except low-rise residential buildings”, the minimum thermal insulation requirement for roof assemblies may need significantly more insulation than previously required. Along with waterproofing and thermal insulation, this latest LEC system can be applied to virtually any existing roof, so there is no tearing off the roof, rather it involves retrofitting it to green and satisfying the norms of the Green Building Council and Cool Roof Rating Council (CRRC). Studies show that they lower roof temperatures by up to 40%, which decreases the amount of heat transferred into a building interior to dramatically reduce the cooling cost. So far a roof has been considered as nothing more than a blanket of protection for a building. This is true in most cases, but a commercial roof can also have a huge impact on the

amount of energy that a building consumes. Usually commercial roofing systems are white which reflect the heat. In fact, a commercial roofing system can lower the temperature of a roof by as much as 30OC. The system reflects as much as 85% of the sun’s solar energy away from the building.

An often debated topic in the LEC system, whether the insulation will be kept over the waterproofing membrane, or vice-versa. But it is desirable to keep the waterproofing membrane over the insulation layer while retrofitting an old building with an LEC roofing system. Both the systems have their own advantages and disadvantages. As such, no particular system is ideal and the system has to be tailor-made based on the client’s requirement in a particular environment.

It is very disheartening to find that most of our codes and specifications in the government sectors are still following 50 year old, traditional practices of tar felting for waterproofing, which is brittle in nature and get damaged after just 2-3 years. Sometimes, layers of brickbat coba are laid on the existing surface, thus adding distress to already distressed structural members. With the technology-driven approach, following a 50 year old practice may cause huge loss to the state coffers. So adopting the latest LEC system would save a substantial amount and would also help the energy crisis being faced by the country today, to some extent.

The collective approach of all the technocrats, builders, developers, architects, engineers and bureaucrats involves adopting this latest LEC system, which provides a guaranteed service life for 20-25 years, and energy efficient and sustainable roofing systems. In fact, the dilemma of balancing between waterproofing and thermal performance for roof assemblies has led to the need for further scientific research with the available materials and systems in the country, before finalizing the correct specification for the country.

Though the issue is being dedicated to waterproofing only, a combo system which deals with both waterproofing and thermal insulation of the roof is most ideal in the present energy crisis era, for which we have given importance to the LEC system. We have covered various aspects of the system and tried to solve the dilemma of waterproofing and thermal performances with their advantages and disadvantages through some selected articles in this issue. We will conclude our ongoing series of publications with the waterproofing of an external facade in the next issue of ReBuild.

From theEditor’s Desk

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Balancing between Waterproofing and Insulation of Vegetative Roof Systems[Excerpts from Professional Roofing of NRCA, November 2011,pp25-29, “The dilemma of balancing waterproofing and thermal performance for vegetative roof assemblies”]

1.0 Introduction

Green or vegetative roof systems perceived by many as durable, sustainable, energy-efficient and high-performing, comprise layered assemblies combining landscaping, thermal insulation, waterproofing components and other elements to provide a functioning system. But there are different approaches to vegetative roof system installation.

Insulation can be placed above a vegetative roof system’s waterproofing membrane to improve waterproofing performance; this often is referred to as an inverted roof membrane assembly. With this construction, water flows through the insulation and compromises the insulation layer’s thermal resistance at the membrane level. This often is recognized as an acceptable compromise to improve waterproofing performance. However, the magnitude of the loss in thermal resistance is difficult to quantify and not well-understood.

2.0 Inverted Roof Assemblies

Design principles for building deck waterproofing assemblies, including plaza systems, place the waterproofing membrane on the roof deck with the protection and drainage layer(s), insulation and additional landscaping components above the waterproofing membrane (see Fig. 1).

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The above layered system is referred to as an inverted roof membrane assembly because the insulation is located above the membrane whereas in conventional roof assemblies, the membrane typically is above the insulation. Building deck waterproofing design principles apply to vegetative roof systems.

Inverted roof assemblies provide the following advantages:

• Fully adhered and loose-laid waterproofing membranes can limit the horizontal migration of water, which assists in the investigation of leaks and subsequent repairs. Water that leaks through the membrane in a conventional roof system can travel variable distances over the roof deck and leak into the building’s interior from the breach in the membrane.

• Conventional roof systems typically include polyisocyanurate insulation, which can deteriorate when exposed to moisture, further increasing the cost and extent of repairs to restore a failed roof system.

• Insulation above the waterproofing membrane reduces temperature cycling, which improves the membrane’s long-term durability.

• Insulation above the waterproofing membrane provides protection from construction activities, components above the membrane and live loads.

• The roof deck provides a rigid substrate to support the membrane; conventional roof systems have the membrane over the insulation or cover board, which is installed to improve the substrate’s rigidity. Compression of insulation resulting from loads can deflect the insulation and cause the membrane to be unsupported. An unsupported membrane has decreased puncture resistance and is prone to seam failure.

• The waterproofing membrane can act as an air barrier and vapour retarder for the roof assembly and is located on the warm side of the insulation, which generally is consistent with design practices to address moisture migration. A conventional roof assembly that lacks an air barrier or dedicated vapour retarder is more likely to develop condensation at the membrane’s underside because of air leakage and moisture migration from the building’s interior. This moisture can cause roof system components to deteriorate; wetting of construction and finish materials that are susceptible to mold growth; and perceived leaks to the building’s interior. These problems are exacerbated in high-humidity buildings (museums and natatoriums, for example).

For inverted assemblies, insulation located above the waterproofing membrane should have low moisture absorption and high compressive strength and resist freeze-thaw damage in climates where it’s a concern. Extruded polystyrene (XPS) insulation is the most appropriate material for this application. XPS boards in buried applications show a loss of 5 to 10 percent in thermal resistance within three to five years that can be attributed to moisture absorption.

Fig. 1 : A vegetative roof system with an inverted assembly (The position of the root barrier varies by design

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3.0 Conventional Roof Assemblies

Although generally in conflict with the preferred waterproofing approach, insulation can be located below waterproofing membranes in vegetative roof assemblies, particularly in retrofit and other applications where inverted assemblies may not be appropriate or desired. This approach is similar to the installation of a conventional roof assembly with the remaining waterproofing and landscaping components placed above the membrane (see Fig. 2).

Designers might choose this system because its base system is consistent with the design of a typical roof assembly and to avoid reductions in thermal performance that are anticipated when installing the membrane and a drainage layer beneath the insulation. Advantages of such systems for vegetative roof assemblies include:

• Improved thermal performance of insulation compared with that of an inverted roof membrane assembly. Drainage below insulation in an inverted assembly can contribute to a reduction in the insulation’s thermal performance because of moisture absorption by the insulation and water and air flow below the insulation.

• The insulation separates the membrane from surface irregularities and roof deck movement.

• Insulation below the membrane can decrease the roof assembly’s thickness and allow the use of polyisocyanurate insulation. Polyisocyanurate roof insulation’s typical thermal resistance is R-6 per 25 mm, according to most manufacturers, compared with the typical R-5 per 25 mm of XPS. Similar to XPS, polyisocyanurate shows a loss in thermal resistance with an estimated in-service R-value of R-5.6. This is attributed in part to loss of insulating gases from foam cells.

It is important to note polyisocyanurate insulation’s low compressive strength requires a cover board, and soil and live loads still may compress insulation and damage waterproofing membranes.

4.0 Drainage Layer Location

Insulation manufacturers generally recommend a single drainage layer be located above the insulation to improve the insulation’s performance. This approach conflicts with building deck waterproofing design principles for the location of the drainage layer for inverted assemblies. Insulation manufacturers’ recommendation to locate the drainage layer above the insulation apparently is to reduce the potential decrease in thermal performance because of the following:

Cold water that flows below the insulation absorbs heat from the roof membrane and drains through the storm water system, increasing heat loss through the building envelope.

Air flow through a drainage layer below insulation increases convective heat loss, increasing heat loss through the building envelope.

Water that drains through insulation increases the insulation’s moisture absorption, which can decrease insulation’s thermal performance over time. If water drains above the insulation, less moisture is absorbed by the insulation.

It has been seen, drainage layers located above insulation are not entirely effective at limiting water at the membrane level or limiting water absorption in the insulation.

Drainage layers typically consist of plastic composite sheets butted to provide continuity with permeable geotextile fabric adhered to the top. Water migrates through the geotextile fabric and can pass through the plastic sheet at joints, holes and other discontinuities; bypass taped seams in insulation boards; and pond on the waterproofing membrane. Ponded water increases a membrane’s moisture absorption, which can decrease the membrane’s service life. At any defects in the membrane (holes and weak or unsealed seams), the hydrostatic pressure of the ponded water can increase leakage to the building’s interior.

Ineffective drainage commonly contributes to leakage through the waterproofing membrane on horizontal surfaces; waterproofing membranes are more effective and durable when membrane-level drainage is provided to facilitate horizontal movement of water to drains. Ponded water also can be absorbed by insulation, countering the expected benefit of placing the sole drainage layer above the insulation.

To improve thermal and waterproofing performance, two drainage layers can be provided—one located below the insulation and a second above the insulation (see Figure 3). The drainage layer above the insulation allows water

Fig. 2 : A conventional roof assembly adapted to a vegetative roof system

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6.0 Thermal Performance

Many interconnected components affect a vegetative roof system’s thermal performance and, as a result, a building’s energy performance. These components are difficult to quantify in isolation, let alone in combination, particularly because of their weather dependency and transient nature.

The thermal performance of inverted roof assemblies can be affected by the flow of water in drainage layers. Cold water passing over the membrane beneath the insulation layer cools the roof deck, effectively short circuiting the insulation.

There would be a significant amount of energy savings during air-conditioning seasons with a vegetative roof system. Figure 5 demonstrates the hourly HVAC energy cost per unit roof area for selected vegetative roof system samples versus the EPDM roof. Energy unit price was considered as 8 cents per kilowatt hour.

7.0 Airflow

The nature of convective thermal effects and airflow in cavities generally is difficult to quantify. The behaviour of a fully enclosed, airtight cavity is fairly well-understood but is an unlikely scenario in an actual building enclosure assembly. Airflows in cavities are a result of differences in pressures and are resisted by friction. These effects are minimal or nonexistent in a conventional assembly because any airflow likely is outboard of the insulation unless discontinuities in the air barrier allow air to migrate into the assembly below the roof membrane. However, air may move within a drainage layer at the waterproofing membrane level in inverted roof assemblies.

The drainage layer in vegetative roof systems is buried and not directly exposed to wind and will provide significantly more resistance to airflow than in exposed systems, such as plaza deck applications with open joint pavers. However, drainage layer edges may be exposed at drains, providing a potential path for airflow

migrating through the soil and moisture retention system to drain; the membrane-level drainage layer allows water that penetrates the top drainage layer to travel horizontally.

5.0 Vegetation

Vegetative roof systems are, in a sense, dynamic. Their performance changes in much the same way terrestrial plant life responds to the varying needs of nature in annual cycles.

In spring, plants grow and provide shade to the roof surface below. As the plants die during summer, the soil is exposed. The darker surface absorbs more heat, which can be beneficial during winter. However, in very cold climates where the latter effect would be most beneficial, the building energy code requirements for insulation thickness and thermal performance are so significant the effect of this dynamic nature may be minimal. That said, whatever benefits this approach provides should be the same regardless of whether a conventional or inverted assembly is used. A roof top vegetative roof system is shown in Fig. 4.

Fig. 3 : A vegetative roof system with an inverted assembly and drainage layers above and below the insulation

Fig. 4 : A view of rooftop vegetative system

Fig. 5 : HVAC energy cost comparison

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if pressure differences exist across a vegetative roof assembly.

The magnitude and effects of convective air currents within the drainage layer are difficult to evaluate, requiring sophisticated analyses and many assumptions. Also, these airflows can affect a roof assembly’s energy performance in opposing ways: increased heat loss because of airflow or decreased heat loss because of the insulating value of a still air layer. This is an area that requires further study to fully evaluate the general energy performance of vegetative roof systems and inverted roof assemblies.

8.0 Moisture

Moisture may lead to roof system degradation and failure; conventional assemblies’ thermal performances can be determined using common methods for typical “continuous insulation above deck” roof systems. These systems’ thermal resistances primarily are a function of the type and thickness of insulation used.

In most modern conventional vegetative roof assemblies, the additional R-value contributed by the soil and other above-membrane materials generally is negligible compared with the insulation. Therefore, evaluating the effects of moisture absorbed by the soil is unnecessarily precise.

9.0 Saving Energy

In another effort to better understand vegetative roof system performance,SPRI and ORNL completed a study showing vegetative roof systems can help reduce heat gains and losses, resulting in significant energy savings in mixed climates. The reduction in heat gains during cooling dominated periods and heat losses during heating-dominated periods shown in the study translates to lower heating and cooling demands for the conditioned space (Fig. 6 & 7).

The SPRI/ORNL study accurately measured the annual cooling and heating loads per unit area of three vegetative roof systems. The study also included side-by-side comparisons with black and white roof systems, as well as a test section with just the growth media without plants.

The study notes the energy savings offered by vegetative roof systems are climate-dependent and affected by the efficiencies of heating and cooling equipment. The study results also show lower membrane temperatures and temperature fluctuations were experienced by the vegetative roof systems than the control black EPDM and white TPO roof systems.

10.0 Conclusions

The popularity of vegetative roof systems and the common perception that they are durable, sustainable, energy-efficient and high-performing makes analysis of such systems’ waterproofing and thermal performances particularly interesting to the industry.

Building deck waterproofing design principles established by the industry for inverted roof assemblies apply to vegetative roof systems and potential reductions in thermal performance often are recognized as an acceptable compromise to improve waterproofing performance. The results of the thermal and energy analysis described provide an “upper bound” for potential energy losses and indicate the heat loss and energy use in inverted assemblies because of drainage below insulation can be significant (6 to 10 percent additional heating energy used).

Further analysis and project-specific evaluations may provide additional information to more accurately predict heat transfer through vegetative roof systems and adjust designs to mitigate the associated increase in building energy use.

Fig. 7 : The SPRI/ORNL vegetative roof study measured heating loads of vegetative and black roof sections indexed to the white section heating load

Fig. 6 : A The SPRI/ORNL vegetative roof study measured cooling loads of vegetative and black roof sections indexed to the white section cooling load

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A Durable, Energy-Efficient, High-Performance and Sustainable Roofing System[Excerpts from the Dr. Fixit LEC Systems Booklet, “Low Energy Consumption Systems for Sustainable Construction-2013” and http://high-performancebuildings.org/pdf/ECM2/ECM2_Technical_Information_Warm-Humid.pdf]

1.0 Introduction

Global temperature has risen significantly over the last century and causes a threat to our eco system. Weather elements like the sun and rain play havoc with the life and durability of concrete structures. This problem is compounded in urban living spaces which are characterised by concrete construction clusters, low vegetation and pollution from various sources. High temperatures lead to health risks of building occupants and higher energy consumption and demand, in turn, stress our environment. Water leakages and seepages also play a major role in impacting the longevity and durability of concrete structures.

Building roofs, in particular, are subjected to high sunlight exposure and rainwater lashing. This calls for an approach to sustainable roofing that can have the following objectives:

• Prevent water seepage and leakage through the roofs

• Ensure the health and comfort of the building occupants

• Reduce energy consumption needs, and most importantly

• Enhance durability of the construction through long term performance and extended service life

It is not only vegetative roofs or roof garden systems that are sustainable – the latest LEC (low energy consumption) roof system is also sustainable. It has integrated waterproofing as well as insulation features. Achieving sustainability with the above objectives is only possible through a well designed building envelope known as LEC system. This green roof system is based on a layered built-up that permanently weatherproofs the roof substrate from rain lash, hot and cold temperature and in turn, leads to high energy savings. This system is the ultimate armour for cool roofs of tropical climatic countries like India, where both rainfall and temperature are high.

2.0 Principle

Cool surfaces are measured by how efficiently they radiate heat (thermal emittance) and how much sunlight they reflect back (solar reflectivity). With this system, the amount of heat that is absorbed into the building’s interior is reduced substantially, leading to greater comfort for the building occupants, lower energy costs and reduced energy needs. This system is designed to be highly reflective and emissive to ensure that the conversion of sunlight to heat

is minimised, and the amount of heat radiated back is maximised. What’s more, the strong built-up system also provides high quality waterproofing, ensuring years of trouble-free performance through this latest LEC system.

3.0 LEC System Components

The dilemma of balancing waterproofing and thermal performance for a LEC system or vegetative roof assembly needs to be assessed based on the site condition. The various climatic factors need to be considered, such as average annual rain fall, maximum and minimum rainfall, intensity of rainfall, highest and lowest temperature throughout the year, temperature fluctuations, humidity and desired performances of the system such as required heating and cooling load, energy savings, service life and overall cost efficiency. With such diverse factors affecting the system, it may not be ideal to design a particular system that can be applicable all over the country. Rather, one needs to choose the functional requirement first, and, based on the climatic conditions, the systems need to be upgraded to meet the specific requirement.

The requirements of an integrated LEC system for tropical regions consisting of a waterproofing system, thermal insulation system and protective finishing system are discussed as follows:

3.1 Waterproofing System

Waterproofing of a flat roof can be done with various types of liquid-applied coating that form a membrane because of their seamless application, along with suitable primer on a well prepared surface. A spray-applied coating forming material with high elongation and water impermeable properties is more suitable. Depending on the required waterproofing performances, the desired dry film thickness has to be evaluated and accordingly the material has to be sprayed to achieve the same result. Else, coverage of the material has to be calculated based on the manufacturer’s specifications.

3.2 Thermal Insulation System

The roof requires significant solar radiation and plays an important role in heat gain / loss, day lighting and ventilation. Depending on the climatic needs, a proper roof treatment is essential. In hot regions, the roof should have enough insulating properties to minimize heat gains. A few roof traditional protection methods are as follows:

A cover of deciduous plants or creepers can be provided. Evaporation from roof surfaces will keep the rooms cool. The entire roof surface can be covered with inverted earthen pots like in northern India. It is also an insulated cover of still air over the roof shading device. This can be mounted close to the roof during the day and can be rolled

to permit radiative cooling at night. The upper surfaces of the canvas should be painted white to minimize the radiation absorbed by the canvas. Consequent conductive heat gain through effective roof insulation can be provided by using vermiculite concrete. However, the heat gain through roofs can be reduced by adopting light coloured roofs having an SRI (Solar Reflectance Index) of 50% or more. The dark coloured, traditional roofing finishes have SRIs varying from 5-20%. A good example of high SRI is the use of broken china mosaic and light coloured tiles for the roof finish as traditional practices in western India, which reflect heat off the surface because of high solar reflectivity and infrared emittance, which prevents heat gain and thus helps in reducing the cooling load from the building envelope.

However, there are many different types of insulation materials to choose from when it comes to applying them on a commercial roof or reproofing an existing structure. The function of roof insulation is to insulate the building against heat inflow from outside during the day. Hence, the heat gain through roofs can be reduced by adopting an overdeck insulation system. In this system a thermal barrier or insulation is provided over the RCC, so that the heat of the sun is not allowed to reach the RCC slab of the roof at all. In this way the surface of the RCC is prevented from heating up. Once the RCC heats up, there is no other way for the heat to escape other than inside the building. So, even though the thermal barrier is provided under the RCC, as in under deck insulation, some heat passes through it and heats up the ambience of the room. This decreases the comfort level of the room and if the building is centrally air conditioned, increases the AC load. Hence, one can safely conclude that overdeck insulation has advantages over underdeck insulation. Overdeck insulation material should have adequate compression resistance, low water absorption, resistance to high ambient temperatures and low thermal conductivity. Overdeck insulation applications are carried out by either:

• Pre-formed insulation materials

• In-situ application

3.2.1 Preformed Insulation Material

Preformed insulation materials are further classified as expanded polystyrene slabs, extruded polystyrene slabs, polyurethane / polyisocyanurate slabs and perlite boards.

• Expanded Polystyrene (Fig. 1) (EPS, Thermocool) – It is a lightweight cellular plastic foam material composed of carbon and hydrogen atoms. It is derived from petroleum and natural gas by-products. Molded EPS does not involve the use of CFCs. Polystyrene is highly economical. EPS meets most of the performance.

• Extruded Polystyrene (XPS) – Extruded Polystyrene (Fig. 2) is an improvement over Expanded Polystyrene material. This material is also comprised of beads / globules which are compressed to form slabs and pipe

sections. In the case of Extruded Polystyrene, the beads are very closely linked to each other so that the material becomes rigid and there is no air gap between the beads. It is a close cells material and a skin forms on the top which stops water absorption.

• Polyisocyanurate / Polyurethane Foam Slab - These are Urethane foam (Fig. 3) insulation materials with low thermal conductivity, low smoke emission and low water absorption.

• Perlite – Perlite insulation is an organic rigid board insulation. It is composed of expanded volcanic glas s (Fig. 4) and wood fibres bonded with asphaltic binders. This makes a rigid board, light in weight, dimensionally stable and good in compressive strength. In western countries, at one time, Perlite was the most common insulation material used for roof insulation. Although still popular, its low ‘R’value, high ‘K’ value and tendency to absorb moisture have reduced its popularity.

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Fig. 1: View of EPS material

Fig. 2: View of extruded polystyrene material

Fig. 3: View of Urethane foam insulation panels

3.2.2 Extruded Polystyrene XPS Board Roof Insulation

Extruded Polystyrene is being widely used for insulation in India, its application method is given as follows:

• The recommended specification is for multiple-layer insulation. A double-layer applications is recommended especially when the total required thickness of XPS insulation is more than 50 mm. Cover boards are considered to be components of a multiple-layer insulation assembly.

• When double-layer XPS insulation is used, the joints of the insulation boards in the top layer should be vertically staggered and offset from the joints in the underlying layer. The end joints of adjacent rows of insulation boards should be staggered, and the edges of abutting insulation boards should be in moderate contact.

• During storage and handling, XPS insulation materials should be protected from the weather. XPS insulation also should be protected from petroleum-based solvents, adhesives and direct contact with certain coal-tar products.XPS insulation should be protected from direct contact with asphalt at temperatures more than about 120°C, and it should not be exposed to flames or other ignition sources.

• It is recommended that XPS insulation boards be covered with a complete roof membrane by the end of each day’s work. For protected membrane roof systems using XPS insulation. It is suggested that the insulation be secured with appropriate ballast by the end of each day’s work.

• At the end of each day’s work, membrane temporary tie-in ply or plies should be installed, adhered to the roof membrane, and adhered or sealed onto the top or bearing surface of the roof substrate to protect the exposed ends of the insulation boards that have been installed that day. Unless water cutoffs have been specified and are to remain part of the finished roof assembly (in the same location where temporary tie-ins are applied), the tie-ins should be cut and adhered or removed entirely before additional insulation is applied.

• When XPS insulation is to be covered by a roof membrane, the roof deck should be relatively smooth, broom-clean and sufficiently dry to provide a proper surface for application of the insulation boards.

• Installation procedures for XPS insulation can vary, depending on the type and density of the insulation, type of

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roof deck, and type of roof membrane and securement method.

3.2.3 In-Situ Spray Applied Polyurethane Foam Technology

Unlike preformed materials, this is applied directly over the roof by spraying. This eliminates a separate fixing procedure. It is formed spontaneously when Isocyanate and Polyol are mixed in the presence of a blowing agent to create a close cell, homogenous, jointless insulation roof cover (Fig. 5). It is designed to combine highly efficient thermal insulation with great ease of application. It is ideal for a wide range of insulation applications, particularly for the roofs and walls of buildings. By nature, liquid-applied Foam Polyurethane adheres strongly to almost any surface, regardless of form. The seamless and monolithic nature of spray foam provides a full proof method of sealing cracks and rendering any surface moisture-resistant and drought-proof. The excellent adhesion of the sprayed material makes mechanical fastening redundant. The comparatively low density of the material adds little weight to the overall loading. Besides external use, sprayed foam can be applied internally as well.

3.3 Protective and Finishing System

Higher albedo materials can significantly reduce the heat island effect. The higher the albedo, the larger the amount of solar radiation reflected back into the sky. Roofs provided with high reflective coatings remain cooler than those with low reflectance surfaces and are known as cool roofs. Cool roofs can reduce the building heat gain and can save summertime air conditioning expenditures. These paints are highly efficient, energy-saving, flexible coatings, made from water-based pure acrylic resin systems filled with vacuumed sodium borosilicate ceramic micro spheres of less than 100 microns in size. Each micro sphere acts as a sealed cell and the entire mastic acts as a thermally efficient blanket covering the entire structure. These coatings are non-toxic, friendly to the environment, and form a monolithic (seamless) membrane that bridges hairline cracks. They are completely washable and resist many harsh chemicals. Roof coats have high reflectance and

Fig. 4: Materials used in Perlite insulation board

Fig. 5 : A view of PU foam insulation system over a concrete slab along with waterproofing and finishing material on top

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high remittance as well as very low conductivity value. They offer UV protection and low VOCs. They display excellent dirt pick-up resistance and retain their flexibility after aging. These roof coats reduce noise transmission and have an effective use range from –40

o C to 375

oC.

3.4 Integrated LEC System of Exposed Flat Roof

Considering the above factors for a pan India location, the integrated LEC system consisting of a combined waterproofing system, thermal insulation system and protective finishing system, can have a long durable service life of 25 years.

The waterproofing material can be sprayed at a rate of 1.5 l /m2 or as per the recommendation of the manufacturer to achieve a dry film thickness of 1 mm, having high elongation upto 1600%, water vapour transmission of 0.2g/h/m2, along with impact resistance and puncture resistance properties.

This system is based on a thermal insulation system consisting of spray applied 2-component PU (Polyurethane) foam, which excludes the possibility of any thermal bridges. Being spray-applied, the thermal insulation is fully bonded to the substrate. A special foam formulation allows a load of 2500 kg/m2 to be installed above the foam. While the standard roofing system with an EPS (Expanded Polystyrene Slab) board of 75 mm thickness achieves a U-Value of 0.414 W/m2K, this latest LEC system just requires a thickness of 40 mm special monolithic foam.

A protective system should consist of geotextile membrane of minimum 150 gsm, over which concrete screed of M20 grade, either from a concrete mixture or from a RMC pump, is placed to achieve a slope of at least 1:100. The finishing layer should be heavy duty acrylic-based white reflective coating or a heat insulating acrylic-based coating, containing hollow microsphere glasses, having solid content more than 60% and a solar reflectance index value of more than 80%.

A typical schematic diagram of a flat exposed roof terrace with both, a waterproofing and insulation system is shown in Fig. 6.

3.5 Integrated LEC System of Roof Garden

A roofing system through shading, insulation, evapo-transpiration and thermal mass reduces a building’s energy demand for space conditioning. The green roof moderates the heat flow through the roofing system and helps in reducing temperature fluctuations due to the changing outside environment. The green roof system is partially or completely covered with vegetation and soil that is planted over the waterproofing membrane. If widely used, green roofs can also reduce the problem of urban heat island, which would further reduce energy consumption in urban areas.

The system components for waterproofing, thermal insulation and protective systems remain the same for exposed flat roofs and roof gardens. But instead of providing a finishing layer, as in the case of exposed flat roofs, a waterproofing system as required for roof gardens or vegetative systems should be introduced. A waterproofing layer with suitable primer has to be placed over the screed, followed by a geotextile membrane of minimum 150 gsm and a drain board. The waterproofing in this case may be either a torch-applied APP or an EPDM membrane. This has to be followed by a soil growth medium and plantation as per the requirement.

A typical schematic diagram of an inverted roofing system for a roof garden is shown in Fig. 7.

Fig. 6 : Schematic diagram for energy efficient high performance roofing system of an exposed flat roof

Fig. 7 : Schematic diagram for energy efficient high performance inverted roofing system for roof garden

4.0 Installation Methodology

The LEC system can be adopted for both, new as well as existing, roof terraces. Retrofitting the existing roof terrace needs more careful attention and assessment before the installation. The roof slab shall be inspected by a specialist and the acceptance for the application of the system is confirmed. The roof area shall be cleaned using a pressure wash or a compressed air system, to ensure that the substrate is free from dust, laitance, debris, etc. Appropriate repair materials shall be applied to make good any cracks, crevices, etc., in the substrate for old roofs. Any pipes or openings or protrusions shall be provided prior to taking up the surface preparation, as shown in Fig. 8.

Since this application would be quite thick, adequate provision must be made to provide water vents to the drain points in the roof, pointing upwards, so that the rainwater will drain with ease into them and pass off into the down-take rainwater pipes. In the case of large roof terraces, wherever the expansion joint is being provided, the detailing should be made as per Fig. 9.

4.1 Installation of Waterproofing System

The waterproofing material can be spray-applied quickly at 100 m2 /h with a special spray gun, reducing crew size and job time. This waterproofing material is UV stable and weather-resistant, but is black in colour. It is lightweight and hence can be applied directly over an existing roof system, eliminating the need for wasteful and costly tear-offs.

4.1.1 Surface Preparation

Surface preparation is generally limited to pressure washing or compressed air cleaning to bond to the substrate.

4.1.2 Priming

Priming is required on some substrates prior to the application of this waterproofing membrane. Primer shall used for asphaltic-based substrates, as well as for concrete, to create a superior bond with the waterproofing

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membrane. An EPDM primer is used for EPDM and PVC substrates.

4.1.3 Application

A specially formulated spray-applied membrane forming shall be applied with a suitable spray gun, at an average thickness of 0.5 mm thickness. It cannot be sprayed through other types of commonly available sprayers without damaging the sprayer or the product. Coverage may vary depending on the profile and texture of the substrate to which it is being applied and on general application conditions. It is best to begin by spraying the lowest side of the roof and then work towards the higher points, to prevent the accelerator from running over clean substrate areas prior to spraying over them. If required, a quick setting repair mortar can be used as flashing and over-spray with this membrane system.

4.2 Installation of Insulation System

Polyurethane foam adheres to most surfaces, horizontal or vertical. It creates a fully-adhered, self-flashing, monolithic roof surface, with none of the critical failure points of most roof systems (seams and penetrating fasteners).With an insulation value of R 2.5 per mm, Polyurethane foam is the most efficient form of thermal insulation.

4.2.1 Surface Preparation

• The surface of application must be thoroughly prepared by mechanical means, to remove all loose particles, laitance, etc.

• Oil and grease, if any, must be de-greased with suitable solvents.

• Any surface undulations, cracks and crevices must be duly filled or repaired with cement sand mortar mixed with latex polymers.

Fig. 9 : Expansion joint detailing of a LEC system

High Elastomeric Acrylic Coating

Spray applied PU foam insulation

Geotextile 150 gsmHeavy duty acrylic based waterproofing coating (1 coat)

Concrete Screed

Cement-sand Angle Fillet (50mm x 50mm)

(Polysulphide Sealant With Backer Rod)

Expansion Joint Filler Board

Filler Board

Highly reflecting coating (2 coats)

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9

5

4

6

7 3

Spray applied waterproofing coating2

12

11

Concrete Roof Slab

1

8

Fig. 8 : Pipe penetration detailing of a LEC system

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4.2.2 Environmental Consideration and Substrate Temperature

Applicators must recognize and anticipate the climatic conditions prior to application, to ensure the highest quality foam and to maximize yield. Ambient air and substrate temperature, and moisture and wind velocity are all critical determinants of foam quality and selection, of the appropriate reactivity formulation. Variations in ambient air and substrate temperature will influence the chemical reaction of the two components, directly affecting the expansion rate, amount of rise, yield, adhesion and the resultant physical properties of the foam insulation. To obtain optimum results, this foaming system should only be spray-applied to substrates when the ambient air and surface temperatures fall within the range of 10°C and 48°C. All substrates to be sprayed must be dry at the time of application. Moisture in the form of rain, fog, frost, dew, or high humidity (> 85 R.H.), will react chemically with the mixed components, adversely affecting the Polyurethane foam formation, dimensional stability and physical properties of the finished product. Similarly, wind velocity in excess of 20 km/h may result in excessive loss of exotherm and interferes with the mixing efficiency, affecting foam surface, curing, and physical properties.

4.2.3 Application Equipment

• 2:1 transfer pumps are required for material transfer from container to the proportioner. The plural component proportioner must be capable of supplying each component within + 2% of the desired 1:1 mixing ratio by volume. Hose heaters should be set to deliver 50°C to 55°C materials to the spray gun. These settings will ensure thorough mixing in the spray gun mix chamber in typical applications.

• Optimum hose pressure and temperature will vary based on the equipment type and conditions, ambient and substrate conditions, and the specific application. It is the responsibility of the applicator to properly interpret equipment technical literature, particularly information that relates to the acceptable combinations of gun chamber size, proportioner output, and material pressure.

• The relationship between proper chamber size and the capacity of the proportioner’s pre-heater is critical.

• Mechanical purge spray guns (specifically direct impingement or DI type) are recommended for highest foam quality.

4.2.4 Application

• Polyurethane foam is sprayed onto the prepared roof surface in two components (a polyol and an isocyanate), that when mixed, expand their volume to form a seamless layer of rigid foam. Within minutes this foam can be walked on and it cures to 90 percent of its full strength in about four hours.

• The Polyurethane foam should be applied @ 50 kg/m3 density or as specified by the manufacturer to form an average thickness of 40 mm.

4.2.5 Precautions and Limitations of PU Foam Application

• If the components are below the suggested temperatures, the increased viscosity of the components may cause pump cavitation, resulting in unacceptable SPF application.

• If the components are above the suggested temperatures, there may be loss of the blowing agent, resulting in diminished yield.

• Extreme care must be taken when removing and reinstalling drum transfer pumps, so as not to reverse the ‘A’ and ‘B’ components.

• Store drums at 20°C to 25°C for a minimum of 48 hours before use.

• Materials in containers should be maintained at 20°C to 25°C while in use. Material temperature should be confirmed with a thermometer.

• Do not configure equipment to recirculate foaming component materials from the proportioner back into the drum.

• Do not recirculate or mix other suppliers’ ‘A’ or ‘B’ component into the material system containers.

4.3 Application of Sealcoat Over PU Foam

Over the PU foam, a single coat of heavy duty, micro fibre reinforced, water-based acrylic coating should be applied with a roller. This shall be done over an acrylic-based primer, which shall be applied over Polyurethane foam. However a second coat of sealer coat may be applied on larger roof terraces.

The first half of the step-by-step application method of a LEC system, right from surface preparation to waterproofing, as well as an insulation system, is shown in Fig. 10.

4.4 Ponding Test

A water ponding test shall be conducted after 5 to 7 days of the seal coat application. Water shall be filled up and retained for at least 24 to 48 hours.

a. Site Preparation

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4.5 Application of Protective Layer

After completion of the ponding test and emptying the water, a geotextile membrane of 150 gsm shall be placed. A bitumen board meant for construction joints in screed shall be placed vertically at 3 to 4 m along the length and breadth of the roof area. Each rectangular bay formed in this manner shall not exceed 12 m2. Concrete screed of M20 grade shall be cast into these bays, maintaining the requisite slope of at least 1 in 100. All around the roof at the parapet wall junction, an angular fillet of 50 mm X 50 mm shall be trowel-applied in cement-sand mortar in 1:3 proportions over the screed, in which the sand shall be cleaned and washed off its silt content. Curing of the concrete screed and angle fillet shall be done as per regular concrete curing practices, by means of regularly wetting a hessian cloth. A few days later, after the curing period, the bituminous filler board shall be exposed by means of a mechanical cutting machine, and lose mortar shall be cleaned or vacuum-sucked to make a clean surface. The grooves formed by exposing the filler board shall be applied with polysulphide sealant of a gun or pouring grade, or a PU sealant. The width and depth of the sealant fill shall not be more than 10 mm each.

4.6 Application of Finishing Layer

After 2 to 3 days of fixing joints with the sealant, a heavy duty, micro fibre reinforced, water-based acrylic coating or a heat insulating acrylic-based coating containing hollow microsphere glasses shall be applied over the screed, primed with acrylic primer, and over the angle fillet, right upto the flashing level on the parapet wall.

The second half of the step-by-step application method of a LEC system, right from the ponding test to the finishing coat, is shown in Fig. 11.

b. Compressed Air Cleaning

c. Application of spray applied water proofing coating

d. Application of spray applied PU foam insulation

e. Application of Heavy duty acrylic based waterproofing coating over Spray applied PU Foam insulation

Fig. 10 : Step-by-step application method of a LEC system (cont.)

f. Completed with heavy duty acrylic based waterproofing coating (2nd coat)

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e. Making Grooves on Screed

d. Angle Fillet over Top Screed

f. Filling Grooves with a PU sealant

g. Coating Screed with highly reflective coating

4.7 Safety Precaution

While spraying, one has to take safety precautions like wearing a respirator in areas of limited ventilation. Otherwise, a basic nose mask and goggles are recommended while spraying.

5.0 Comparison of Performances

The performance of this latest system is being considered by comparing various factors such as thickness of material, dead load per unit surface area, energy efficiency, cooling load, cost, durability and environmental sustainability.

As per ECBC (Energy Consumption Building Code) norms, the insulation requirement of roof should have minimum R value of 2.1 m.C/W of insulation alone and maximum U-factor of 0.409 W/m2C of overall assembly for all 5 different climatic zones of India. Considering

a. Water Ponding Test - 24 Hours

b. Fixing Filler Boards Over Geo Textile

c. Casting Concrete for Screed h. Completed Roof With Heavy duty acrylic based waterproofing coating/ highly reflective coating

Fig. 11 : Step-by-step application method of a LEC system

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It can be seen from Fig. 13 that the cooling load efficiency of insulation material used in LEC system is 51 % less than EPS reference material while cooling load efficiency of brickbat coba system is 2305 % higher than EPS reference material. One can compare the energy efficiency of this insulation material used in LEC system over brickbat coba system. But still we are using the old traditional practices of brick bat coba even providing layer after layer for waterproofing as well as insulation. This shows still how much backward we are in adopting this latest material though the technology is available at our door step.

Considering the performances and durability, this system is meant for some decades not for few years. It is unwise to compare the initial cost of this system with traditional or any other system since the initial cost will be too high. But considering the benefits of energy saving and durable waterproofing performances in a long run, the system would be definitely economical. Hence the life-cycle-analysis for cost and environmental sustainability must be analyzed before taking a final decision for adopting a high performance waterproofing and insulation system.

6.0 Conclusion

Whether a LEC system or a roof garden / vegetative system, the percentage of adoption of such green roofing in India is very minimal as compared to other developed countries, because of a lack of awareness, the mindset of adopting a new system and the initial cost factor. The energy savings usually cover the cost of the roof system in a few years, and, by placing the insulation on the outside of the envelope, the foam reduces building expansion and contraction. The initial cost of installation of the system may be higher, but considering the cost for a longer period, or considering life cost analysis along with environmental benefits, this system will be more sustainable in all aspects like economical, environmental and technological issues. When it comes to roof waterproofing, sustainability has mostly not been the deciding factor. The main focus is laid on waterproofing properties but not on insulation. However, the latest LEC system is a complete roofing solution that combines thermal insulation and leak proof waterproofing for sustainable roofing, and is very much suitable in our tropical climate. Being a system which can be part of any LEED certification, this LEC system offers ecological and economical advantages against standard systems. This saves resources and is part of the LEED / GRIHA certification.

the minimum requirement of insulation for the R value for day time use of buildings other than hospitals, hotels and call centres, the required thickness of different insulation materials are proportionally shown in Fig. 12. It can be seen from Fig. 12 that the thickness of insulation material in LEC system is 50 times less than brickbat coba, 2 times less than EPS material and 1.6 times less than XPS type of material to achieve the same objective of getting R value of 2.1 m.C/W. The dead load of this insulation material in LEC system is only 1.9 kg/m2 comparing to the dead load of 2990 kg/m2 of a brick bat coba system. Thus this LEC system is very light weight and contributes hardly any dead load to the roof slab.

India being a tropical climate, energy saving calculation is based only on measuring cooling loads. But in western countries both heating and cooling loads need to be evaluated for the same purpose. A comparison was made by calculating cooling load efficiency of different insulation materials available in India for which most commonly used EPS material was taken as standard reference material and the same is shown in Fig. 13.

Fig. 13 : Expansion joint detailing of a LEC system

Fig. 12 : Comparison of thickness of different insulation material for meeting the requirement of ECBC for R value 2.1 m.C/W

•Open ProgrammeTopic : Building Maintenance, Waterproofing and General Repair Date : 23 – 24 January 2014Venue : DFI-SPR, Mumbai

•Collaborative ProgrammesTopic : Waterproofing of BuildingDate : 30 January 2014Venue : LIC Office, Jamshedpur, JharkhandParticipants : LIC Engineers, Jharkhand

Topic : Waterproofing of Basements, Wet Areas and Retaining Structures Date : 25 February 2014Venue : IEI, Jamshedpur, Jharkhand

•Students Development ProgrammeTopic : Waterproofing of Concrete Structures Date : 26 February 2014Venue : NIE, MysoreCollaboration with : ACCE, Bangalore

The Institute’sActivities

Topic : Structural Diagnosis and Repair of RC StructuresDate : 28 February 2014Venue : Global Academy of Technology, BangaloreCollaboration with : ACCE, Bangalore

Topic : Protection Measures against Corrosion in RCC StructuresDate : 1 March 2014Venue : JSS Institute of Technology, BangaloreCollaboration with : ACCE, Bangalore

Topic : Protective Coatings for Durable StructuresDate : 1 March 2014Venue : KIIT University, Bhubaneswar, Odisha

Topic : Waterproofing of External Building ElementsDate : 3 March 2014Venue : C.V. Raman College of Engineering, Bhubaneswar, Odisha

Forthcoming Training ProgrammesDFI-SPR has scheduled the following training programmes for the upgradation of knowledge base of Practising Engineers, Waterproofing and Repair Contractors, Consultants, Architects, Faculties and Students from Engineering Colleges.

Sr. No.

Date Venue Topic Fees Details of the topic

1 25 & 26 Sep 2014

DFI – SPR, Andheri (E), Mumbai

Diagnosis and Condition Assesment of Concrete Structures – An approach to Repair

` 4200 • Manifestation of distresses in RC buildings

• Structural health monitoring and damage rating

• Non destructive test

• Semi / Partial destructive tests

• Specific tests – Infrared thermograph, petrography, chemical testing etc.

• Approach to repair – an understanding

• Case studies

2 1 to 12 Dec 2014

DFI – SPR, Andheri (E), Mumbai

Entrepreneurship in Waterproofing, Structural Protection and Repair of Concrete Structures

` 9000 • Introduction to Concrete buildings

• Waterproofing – practices, materials and application techniques

• Building maintenance and general repair

• Safety, health and environmental aspects

• Entrepreneurship development

• Practical sessions

• Site Visit

Corporate Training Programme In addition to the above scheduled programmes, we do organize separate corporate training programmes on specific topics as per the needs of the customer.

Contact Details:Mr. Tirtha Pratim Banerjee Dr. George Varghese

Phone: (022) 28357683, Mob.: 9930650145 Phone: (022) 28357499, Mob.: 9819978211

E–mail: tirtha.banerjee@pidilite.com E–mail: george.varghese@pidilite.co.in

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CONSULTANCY SERVICES OFFERED• All type of Industries, Infrastructure, Marine

Structures & other Buildings

• Structural Audit

• Periodical health check up

• Diagnosis of structural defects and recommendation for suitable repair and rehabilitation

• Leakage Investigation of Buildings and recommendation for remedial water proofing

17

Advanced Diagnostic Laboratory & Consultancy Services

NABL accredited laboratories for NDT and Chemical Testing in accordance with the standard ISO/IEC 17025:2005

TESTING FACILITIES• Quality of concrete by Ultrasonic Pulse Velocity

• Quality of concrete by Digital Schmidt Hammer

• Concrete cover mapping by Profometer

• In-situ strength of concrete by core extraction

• Rapid Chloride Penetration Test (RCPT)

• Corrosion analyser by Galvapulse

• Infra Red Thermography

• Microscopical analysis of thin concrete samples

• Chemical analysis of concrete related materials

For availing any of the above services, please contact:

Mr. E. Gopalkrishnan,

Phone : +91 22 2835 7822,

Mobile : +91 9769222667

E-mail : e.gopalkrishnan@pidilite.com

Petrography laboratory

Chemical analysis laboratory

Measuring the rate of corrosion in steel reinforcement by Galvanostatic Pulse measurement

Measuring the cover depth with a Profometer

IR Thermography to detect delamination and voids of concret as well to find out the source of water leakage and location of water pipe

18

International Journal of 3R’s (Repair, Restoration and Renewal of Built Environment)

ISSN 0975-8968,

Annual subscription : ` 1800 Outstation cheques : ` 100 extraPeriodicity : QuarterlyWhy not write for International Journal of 3R’s?

• Research papers, Reviews, Case studies (maximum 15 manuscript pages) and Point

of View (maximum 5 manuscript pages) can be sent by email to editor3r@pidilite.co.in and info@drfixitinstitute.com.

Also, papers can be submitted online on http://www.drfixitinstitute.com/articles/index.php.

HEALTHY CONSTRUCTION MANUAL - 1

Joints & Sealants

ISBN 978-81-909802-0-3,

Price : ` 300 Postage : ` 25 for Mumbai and ` 50 for outsidePages : 53

The Manual on “Joints and Sealants” covers different types of joints and their need for providing in concrete structures. It explains the movement of joints and how to design such joints at different locations consisting of different materials of cast-in-situ as well as precast constructions. It also provides solutions to seal those joints with different types of sealants and also guides for selection of materials for structures with fluid pressure and industrial floor joints and how to install those sealants including use of water stops / waterbar. The safety, health and environmental aspects are also covered.

1

HEALTHY CONSTRUCTION MANUAL - 2

Protective Coatings (For Concrete & Masonry Surfaces)

ISBN 978-81-909802-1-0,

Price : ` 400 Postage : ` 25 for Mumbai and ` 50 for outsidePages : 104

The Manual on “Protective Coatings for Concrete and Masonry Surfaces” is aimed to guide the practising and maintenance engineers in selecting a suitable protective coating for durability of the concrete and masonry structures and to provide details of method of applica-tions, standards and specifications for executing the jobs at site. The various topics covered: Introduction, Properties and Test Methods, Characteristics Performances of different Coatings, Application, Quality Assurance, Safety, Health & Environment and Preparation of Tender documents including Appendixes, List of Relevant standards, equipment and their function.

Publications

For subscription of above Journal and purchase of Manuals, please send your Demand Draft / Cheque in favour of “Dr. Fixit Institute of Structural Protection & Rehabilitation” in the address given on overleaf or contact Ms. Clotilda Dsouza on Tel.:022–28357188, Mob.: 09594420601

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DFI-SPR

VISIONTo become a premier national knowledge and skill development centre for capacity enhancement in waterproofing and other areas of repair, restoration and renewal engineering based on sustainable and green technologies.

MISSIONTo act as a platform of national and international networking for sharing of knowledge and practices in the fields of waterproofing, repair, restoration, and renewal engineering in the context of life cycle assessment of the built environment for adoption of best practices by the country’s construction industry.

Editorial Advisor : Dr. A. K Chatterjee, Editorial Office : Mr. S. C. Pattanaik, Editor Printed & Published by Dr. Fixit Institute of Structural Protection & Rehabilitation, Ramkrishna Mandir Road, Post Box No.17411, Andheri (E), Mumbai 400 059 INDIA. Tel +91-22-28357973

DFI – SPR : ACTIVITY CHART

Reader’s Feedback & Interaction SolicitedOur Newsletter is focused on good concreting practices, waterproofing, repair, rehabilitation and maintenance of concrete structures and buildings. Any reader, who wishes to contribute his or her experience or achievements in this field to our Newsletter for wider dissemination, may send the details to:

The Editor – ’Rebuild’Dr. Fixit Institute of Structural Protection & Rehabilitation

C/o Pidilite Industries Limited Ramkrishna Mandir Road, Andheri (E), Mumbai 400 059Tel : 022 – 2835 7973E-mail : suresh.pattanaik@pidilite.co.in info@drfixitinstitute.comVisit us at : www.drfixitinstitute.com