Arch 330 Thermal & Moisture Protection

Roofing Systems

Roofing Systems

073000 Steep Slope RoofingShingles and ShakesRoof TilesNatural Roof Coverings

074000 Roofing and Siding PanelsRoof and Wall PanelsSiding

075000 Membrane Roofing076000 Flashing & Sheet Metal077000 Roof and Wall Specialties and Accessories

Division 7

078000 Fire and Smoke Protection

079000 Joint Protection

Joint Sealants and Expansion Control

Low Slope - Disadvantages

• water drains slowly

• standing water can cause deterioration

• structural movement - tear the membrane.

Low Slope - Advantages

• can cover building of any horz. dimension

can serve as

• balconies, decks, patios, landscaped gardens.

Name: Kallen Hawthorne ID# 10596914

Item Spotted: Flat roof

Observations: This is not a good roof design for wet climates. There is constantly puddles of water on the top of this roof.

Location: PEB, WSU Campus

Steep Slope• drains quickly• can be covered with roofing material of

small overlapping units- shingles of wood- slate- artificial composition- tiles of fired clay or concrete- bundles of reeds (thatch).

Steep Slope

• Thermal expansion / contraction minimized

• Movement in structure is minimized

- by the ability of small units to move with - respect to one another.

• Water vapor vents from the interior through the loose joints in the roofing material.

Name: Kallen Hawthorne ID# 10596914

Item Spotted: A combination of a flat and gamble roof

Observations: This building has a very interesting skyline because of the combination roof. However if one was to look closely at the picture, one con see puddles of standing water.

Location: Smith Gym, WSU Campus

LOW SLOPE ROOF(not FLAT) < 3:12 pitch

• Min Slope  

• 1/8” per 1’-0” or 1:100

• 1/4” per 1’-0” or 1:50

Low < 3:12 pitch

3

12

1/4

Roof Slope

• Slope Roof to direct water towards drainage points- counter-acting structural deflection.

• Depending on size of deck expansion joints should be provided to - control expansion and contraction and- satisfy requirements of membrane.

• Membrane should be laid on flat surface.

FLAT ROOF - COMPONENTS 

• DECK

• THERMAL INSULATION

• VAPOR RETARDER

• MEMBRANE

• FLASHINGS

• DRAINAGE COMPONENTS

Deck:Types of structural deck used for low slope roof• Plywood over wood joists

• Solid wood decking over heavy timber framing

• Corrugated steel decking

• Panels of wood fiber bonded together with portland cement

• Poured gypsum over insulating formboard

• Sitecast concrete and precast concrete

Insulating Deck Boards – wood/glass fibers

Truss Tee Purlins + slab of gypsum/lt wt conc

Thermal Insulation

• Below the Deck

• Between Deck + Membrane

• Above the Membrane

Thermal Insulation: Below the Deck• Leaves the deck and membrane exposed to

full range of temperature.

• Batt insulation of glass fiber or mineral fiber between wood joists

- or on top of a suspended ceiling assembly.

• Vapor retarder below insulation**

(Vapor retarder on warm side of insulation)

Insulation: Between Deck and Membrane• Rigid panels of insulation, light weight concrete.• Protects deck from temperature extremes.• Membrane subjected to extreme temperature

variations.• Moisture trapped in insulation can damage

insulation and deck.• Place vapor retarded on inside of insulation and

vent insulation to release moisture.

Insulation: Above the Membrane• Membrane protected - extremes of temperature.• Membrane on warm side of insulation - immune to

vapor blistering.• Insulation must be a material which is not effected

by wet and will not disintegrate - extruded polystyrene board

• Insulation board adhered in bed of hot asphalt or laid loose.

• Layer of ballast laid over insulation.

Insulation: Above the Membrane• Ballast

- crushed stone- thin concrete layer factory laminated to upper surface of insulation board- interlocking concrete blocks.

• Membrane ages little protected from sunlight and temperature extremes - despite presence of moisture.

• Rigid insulation - mechanical fix to deck preferable.

Insulation above the Membrane: Other names for this system• Inverted roof

• Upside down roof

• Protected membrane roof,

+- 20years old

Vapor Retarder

• 2 sheets asphalt saturated roofing felt

• In cold climate on warm side of insulation.**

• In hot humid climate/with air conditioning - on outer side of insulation**

Membrane

• Built up roof membrane

• Single-ply roof membrane

• Fluid-applied roof membrane

Built-up membrane• 2-4 Layers/ plies of felt

asphalt impregnated, bedded in bitumen

felt: cellulose fibers/glass fibers +asphalt

• Felt laminated in overlapping layers

• Layer of aggregate (crushed stone)

Built-Up Membrane• Bitumen - asphalt derived

• For low pitch roofs - coal tar bitumen or coal-tar pitch used-

- greater resistance to standing water

• Asphalt and coal tar are applied hot

• Aggregate

• Insulation

• Felt

• Conc. Deck

• Aggregate

• Felt

• Insulation x 2

• Metal Deck

• 4 ply felt + hot asphalt

Single Ply Roof membrane

• Single layer• More elastic - less cracking/tearing• Fixing: adhesives, ballast,

concealed fasteners, mechanical fasteners.

• Protective coating

Single Ply Roof Membrane

• EPDM , synthetic rubber(ethylene propylene diene monomer) 

• NEOPRENE (polychloroprene)synthetic rubber compound 

• PVC (polyvinyl chloride)vinyl - thermoplastic compound

Single-Ply Membrane

Aluminum Faced

Single-Ply Membrane

Fluid Applied Membrane

• domes, vaults, complex shapes

• roller or spray gun, applied

• several coats - rubbery membrane.

Built-Up + Single PlyBallast• loose stone aggregate • precast concrete blocks.• Ballast holds the membrane in place against

wind uplift• Protects membrane from ultraviolet light

and physical wear.• Increase the fire resistance of the roof

covering.

Traffic Decks-walks, terraces, parking – on low slope roof(a) Heavy square paving slabs or stones –open joints

on blocks of plastic or conc on roof membrane

(b) Open Jointed Paving Blocks on A drainage layer of gravel or porous concrete leveled over the membrane

• Water falls through the joints and is drained away by the membrane below

• Membrane is not pierced.

Structural Standing Seam Metal Roofing for Low Slope Roofs:

• Proprietary systems of standing seam metal roofing

• Used as low slope roofs - 1/4" in 12 "(1:48).

• The folded shape - stiffness - support itself + a normal snow load between purlins without the need for structural deck below.

Mechanical Fix

Through Insulation to Deck below

Hot Application of Layers

Stone ballast on Insulation on Membrane

Mechanical Fix

Steep Slope >3:12 pitch

3

12

11.25º

Steep Slope >3:12 pitch

• Drains quickly,

• Small overlapping units - Shingles

• Expansion and contraction and movement

• Water vapor vents

Steep Slope Roof – Systems3 Categories of Covering

• Thatch

• Shingles – wood, asphalt, slate, clay/conc

• Sheet Metal – lead, copper, terne, aluminum

Steep Sloped Roof Systems• Typically insulation and vapor retarder

installed below the roof sheeting or deck.

• Underside of deck is exposed as a finished surface

- vapor retarder and rigid insulation above the deck below roofing layer of plywood (nailed over the insulation panels as a nail base for fastening shingles or sheet metal).

Insulation

Steep Sloped Roof

Typically insulation and vapor retarder installed below the roof sheeting or deck.

Insulation

Steep Sloped Roof

Underside of deck is exposed as a finished surface

Flashing @ all

junctions

Thatch

• Bundles of reeds, grasses or leaves,

• Labor intensive

• Highly insulative

• Attractive

• Codes limit its use

• Not fire resistant

ShinglesSmall size unit, applied to roof in overlapping

layers - staggered vertical joints

• wood shingles/ shakes

• asphalt shingles

• slates

• clay tiles and concrete tiles.

• PV – photovoltaic

Shingles

• Each type of shingle, slate or tile must be laid on a roof deck - that slopes sufficiently to assure leak-proof performance.

• Min. slope for each material are specified by the manufacturer and code

Wood Shingles:

• Thin, tapered slabs of wood, SAWED from short pieces of tree trunk

• Grain parallel to the face of the shingle.

Wood Shakes• Split not sawn

• Rough face texture,

• North US - wood shingles/ shakes are Red cedar, White cedar,

• Redwood - natural decay resistance.

• Wood roof covering moderately expensive, not highly resistant to fire unless pressure treated with fire retardant chemicals.

Asphalt Shingles• Asphalt impregnated felt - faced with mineral

granules.• Die cut from sheet, typical size 12" x 36".• Slotted twice - smaller unit.• Inexpensive, quick to install, moderately fire

resistant.• Expected life time of 15 to 25 years.• Laid on asphalt saturated felt paper in two layers.

Slate• Split, trimmed to size and punched or

drilled for nailing.

• Fire resistant,

• long lasting,

• relatively expensive,

• laid in over lapping layers.

Tiles – Clay, Concrete

• Glazed and unglazed

• Concrete less expensive than clay roof tile.

• Typically heavy

• Durable

• Highly resistant to fire

• Expensive in first cost

Architectural Sheet Metal Roofing:• Relatively high in first cost

• Last for many decades.

• Galvanic action should be avoided in the roof installation.

• Beware of water run-off also re galvanic action from one metal to another.

Seaside, Gulf Coast – The Truman Show

Strawbale, Potlatch, Idaho

Lead, Copper: Sheet• Used since ancient times.

• Self-protecting metal - last many decades.

• Installed in sheets using systems of joining and fastening

• Maintain water tightness at the seams.

• Seams especially standing & batten seams create a strong visual pattern.

Lead, Copper: Sheet• Lead oxidizes to a white color.

• Copper turns blue-green in clear air, black in an industrial atmosphere.

• Chemical treatments and coatings can be applied to preserve a desired color.

Other Sheet MetalsAluminum,

Zinc Alloys,

Stainless Steel Sheet Metal Roofing

• Can be used in same way as copper, lead and terne