ALLTECH CONSULTING GROUP

POINTS OF INTEREST

History

Why they fail

Waterproofing

Dig it up

Sumps

Introduction

Each week I select a question from a reader, generally chose one that I may have had more then one similar request. This summer however the number of questions about block basements, damp to outright wet, cracks and repairs, how to fix and not get stung and how to insulate has been a weekly inquiry. It is a sign of a very wet summer I suspect. This booklet will cover some history, pros and cons to block and go on site with a foundation contractor as they repair and waterproof a block basement. I hope you find it interesting and informative.

ASK THE

INSPECTOR

6 Part Series

Block

Basements

Cam Allen L.I.W. RHI

Phone: 613-546-9876

cam@alltechconsultinggroup.com

By the Block

Up until the 1980’s concrete block

was the basement of choice.

They are reasonably priced, fairly

simple to lay provided your foot-

ings are level and if you need to

make some adjustments for square

of level it can be “picked up as you

build your rows of blocks.

If you are hiring a mason to build

your block basement he will charge

you “by the block” to assemble it.

Around 1950 we started brushing

road tar or bituminous tar onto the

blocks in the belief that this would

stop water from penetrating the

blocks. We thought we had the

wet basement issue solved……..oh

how wrong we were!!”

more uniform in integrity, but they are still made of Portland Cement, sand and an

aggregate of some form.

Gravel is used, so is shale and slate in some manufacturing processes. The mix for

blocks usually contains more sand than gravel and water, making it a stiffer mix so the

blocks hold their shape. Most modern block manufactures use some manner of com-

paction to help make the blocks consistent. An average run of blocks from mix to

pour, then curing and then put in a steam room to reach an even temperature and

then they are allowed to dry takes about a day. We generally see the grey hollow

concrete block. There is however many other kinds including architectural designs

used on large buildings for example.

If block basements were so good and reasonably priced, why have we moved to

poured concrete and insulated concrete foundations? The answer is longevity, re-

duced water invasion and better insulation values. We started using basements for

living space after WW2 and along came the problems. The first thing we found out

was the tar we applied is a damp proofing, not a water proof coating. It often dried

out, did not seal cracks and on average failed in its intended use. Within 3-5 years

depending upon the soil and water concentration it was sitting in the moisture would

begin to invade the blocks. An average modern block will absorb up to 3-4 lbs of wa-

ter…per block. The hollow cavities will hold up to a gallon and half of water.

We did not use below grade drains with any consistency until the 60’s and even then

they were a clay tile that quickly filled with silt or tree roots.

Improper drainage around the home, lack of eves trough extensions, the movement

of soil due to what is know as the freeze-thaw cycle, lack of proper anchoring at the

sill plates, moving equipment too close to the building, it’s a long list of issues that

Early concrete blocks weighed over 50lbs a piece, today they average anywhere from 25-30 lbs per block

History of the Block

We shall start by explaining the some

of the history of blocks, how they are

made and some of the “quirks” of a con-

crete block basement. While it’s gener-

ally considered that the Romans in-

vented concrete and used it extensively

in their massive buildings the use of a

uniform concrete block did not evolve

until the mid 1800’s. Many contractors

used hand made molds and poured their

own. The first concrete block building in

North America is located in New York

City, it was built in 1837. Thanks to Eng-

lish Inventor Joe Aspidin who invented

Portland Cement in 1824 it allowed the

development of concrete blocks. In 1868

a company in Chicago called G.A. Frear

got the first patent for manufactured

concrete blocks. They were designed

with a stone chiseled pattern to look like

a stone foundation, for a lot less money.

By 1900 a gentleman by the name of

Harmon Palmer had invented a cast iron

machine that mass produced hollow

concrete blocks. Coupled with the devel-

opment of reinforced concrete in 1849,

by World War 1 the use of steel, con-

crete and concrete blocks for large scale

buildings was well under way.

The actual method of making concrete

blocks has not changed dramatically

since it original development. They are

lighter and stronger now and certainly

2

Good blocks go bad

The number one issue with

a block basement is mois-

ture; blocks are not water-

proof…period. Water will

penetrate any mortar crack,

open seam or just about

any opening for that matter

and we all know that the

blocks themselves are po-

rous.

I have seen cases where a

contractor drilled a hole in

the second course of blocks

and the water actually

flowed in.

The CMHC guide to damp

basements has a good list of

reasons why basements

leak. Ineffective or non-

existent eve trough and

downspouts are top of the

list. Lack of slope away from

the building, poorly draining

backfill around the base-

ment, ineffective window

well drains, defective or

missing below grade drain-

age systems are the com-

mon culprits for a wet base-

ment. There are two other

issues which are serious and

very difficult to fix, that is a

basement built in an area of

high water table and one

build in a valley or on the

side of a long sloping grade.

Why they fail

affect block base-

ments. We learned

some time ago they

were only capable

of bearing a build-

ing about five times

less the weight

than a poured con-

crete foundation.

Block basements

were an evolution

in modern home

assembly. After this

many years we

have learned their

shortcomings and

fortunately we have developed ways to improve them, unfortunately at some consid-

erable cost in many cases.

3

Clogged clay drains can’t do the job

If you have a choice in basements between ICF, poured concrete or block I think you

will find most reputable contractors will list them just like that with a block basement

last. Check the yellow pages for waterproofing contractors that are listed, few of them

fixed poured or ICF.

A block basement with moisture issues is usually fairly easy to detect, provided its

not covered in drywall or paneling. If you have a white chalking along the first or sec-

ond row of blocks you can bet you have a drainage issue. This chalking is called efflores-

cence and is not uncommon in a block foundation, especially an older one. Efflores-

cence by itself is not that harmful, what it means is there is a salt content in the blocks

or the external ground water seeping thru and depositing this white crystal like powder

on your block wall.

There are as many reactions from a wet basement as there are terms. Mold, Mildew

and that “Damp Smell” are all signs of a water issue. Mold or rot at the end of your

floor joists or along the sill plate are also a sign. The CMHC publication “A Guide to Fix-

ing your Damp Basement” is a good starter manual. Contact CMHC at 1-800-668-2642

and ask for catalogue number NH15-72/2007E..

Moisture in a block wall can usually be fixed by excavation and installing any number

of membranes around the foundation. We will discuss that next week. The other issue

is foundation failure and this is usually caused by seasonal expansion and contraction of

the soil around the basement which puts pressure on the actual block foundation. Dur-

ing the freeze-thaw cycle this pressure builds up against the wall and often causes hori-

zontal cracks along the mortar lines. This can and does lead to a bow in some block

walls. I generally see this at or near the frost line, anywhere from the fourth to sixth

row of blocks in a standard basement which is usually 11 rows high. The next defect

that I see too often is the lack of anchors in the sill plate and the soil pressure is actually

pushing the wall vertically inward. While not as common, a shear crack at the base or

second row of blocks is usually caused by poorly drained soil that has moved these

blocks inwards. These types of block failure are more common than many people think

and usually mean major foundation restoration or replacement if not caught in time.

“I shake my head to think that less than twenty bucks of eves trough extension could have saved what could quite easily be a five figure repair. “

Another common problem is step cracks that follow the mortar line. These can be the result of settling or a poorly installed

footing base. This is reasonably common in many block basements and if there is no continued movement there are some

reasonable repairs available for this type of crack. A wall with a bulge or a full bow can often be stabilized by means of but-

tress work or infilling the blocks with rebar and concrete slurry. I have seen a Kevlar wrap used on a bowed wall and I have

also seen steel columns installed that were anchored to the pad and the floor joists. The benchmark I have seen used is the

under an inch for a bowed wall. While the rebar and slurry does work it has some drawbacks. Getting an even pour inside a

block wall is difficult and air pockets are not uncommon. Feeding a 6-7 foot long piece of rebar inside a block wall is a daunt-

ing task; it takes patience and a skilled hand. Any block wall with more than a ¾-1” of displacement should be excavated and

brought back to plumb or replaced.

Drainage and eves trough discharge are the two major issue as we have stated and I can’t stress enough how important this

is. Every time I get called to a basement problem it’s often a home that is 25 plus years old, the downspout discharge is the

elbow on the end and the wall has a major crack. I shake my head to think that less than twenty bucks of eves trough exten-

sion could have saved what could quite easily be a five figure repair. If you have a block basement and see activity in your

wall, don’t delay getting a professional foundation company to look at it. Caught in the early stages you can save thousands

of dollars.

This is the third in our series on block

foundations and this week we look at the

numerous kinds of materials, coatings and

membranes on the market that are used

to rectifying a wet block basement. One

thing to get clear from the start, the terms

damp proofing and waterproofing that

are often used by some unscrupulous

contractors as the same thing….they are

not! Damp proofing is coating that applied

to resist water vapor, it’s generally an

asphalt based coating not unlike the

driveway sealer you put on your asphalt

driveway. In an extremely well drained

soil around a home they will have some

effect but those of us in the trades are

fully aware it looses its effectiveness in

less than 5 years. Waterproofing is just

that, a system to effectively prevent wa-

ter from entering your block basement.

This is done by excavating around your

home and applying a waterproof system.

The next myth is the roll on…brush on…

spray on coating that is applied to the

inside of your basement walls. Think of a

plastic cup with a small hole drilled in it. If

you apply the band-aid on the inside and

fill it with water the entire band aid is held

in place by the water. If you apply it on

the outside you are reliant upon the adhe-

sion abilities of the band-aid. In effect if

the porous blocks are receiving the mois-

ture we all know they do then this kind of

coating has a tough job ahead of it, one I

have yet to see as long term effective.

There is one interior water soluble rub-

berize material called Blue Max that ad-

vertises itself as a waterproof paint. If you

read the specs closely you will find they

recommend 2 gallons per 100 sq ft and

application to the thickness of a dime. In

an area of casual dampness it may be

worth a look, for repeated dampness or

water invasion I would be hesitant.

Waterproofing

Coating Options

There are also a number of differ-

ent kinds of brush…roll….spray on

rubberized coatings on the market.

One maker is called “Tuff-N-Dri. Its

product is a spray on coating called

“Code Blue” (there’s that blue

again!) This product is only applied

by installers who have been

trained by Tuff-N-Dri. One of the

largest manufacturers of sealants,

coatings and membranes is Bakor.

They are the makers of Yellow

Jacket and Blue-Skin. They also

manufacture a line of liquid ap-

plied membranes that are very

popular with reputable foundation

companies. Some installers will

cover their liquid membrane with

rigid foam insulation. This has two

benefits, it helps reduce the cold

intrusion into the foundation,

similar to an ICF foundation and

help protect the liquid coating

from any damage from rocks or

lumps of soil in the material used

to backfill the opening around your

foundation. There are other kinds

of waterproofing systems on the

market; Thermadry is a system of

2’ by 8’ tongue and groove panels

that are channeled to deflect wa-

ter for example.

Now that we have got the myths out of the way we can look at the different kinds of actual external coatings and membranes that are

on the market. It is a long list so I am going to stick to the most common types. Bentonite clay is a powdered mix that is also used in some

toothpaste. It was the first recognized waterproofing material and entered the residential market in the mid 60’s.

Once the mix is prepared by a trained installer it swells up to form a sticky gel upon application. It is also available in sheet form. The draw-

back to this material is it must be shielded from rain and if there is any free flowing ground water it will erode it away.

“John McEwen from Eastern Ontario Foundation has fought for years to get this included, as have many other reputable contractors…”

The majority of reputable foundation contractors utilize a rubberized liquid coating

or some form of continuous membrane. There are numerous kinds of membranes on

the market. Yellow jacket is one type that is applied over a preparation coating and is

set into the coating. It is an open weave glass fabric material that is colored so the

installer can see that they have covered it fully. It is applied in layers to form a water-

proofing covering. It seems that the word “Blue” is attached to many foundation ma-

terials. One make is called “Blueskin”, it is a self adhesive membrane that is applied

over a sealing primer compound that has been applied and cured. Another mem-

brane is called dimple wall and is made by a couple of companies. This rubberize sheet

is designed to offset the actual membrane from the wall by 5/16” by means of a dim-

pled surface. The manufacturer claims it keeps the soil away and allows any dampness

in the blocks to condensate outwards onto the membrane and then drain down to the

drainage tile for removal.

Last week we looked at the different kinds of coatings and membranes that are used on block basements to correct dampness and outright water invasion. This week we look at what should happen when it comes time to dig up a basement and correct the problem. Actually we are going to look at how a reputable contractor should begin. Over the years I have had numerous conversations with responsible foundation contractors and every conversation contains the comment about the lack of a permit for this type of work in the building code. The OBC steers clear of this issue and when you consider the cost along with the multiple num-

bers of “quick buck” contractors in the foundation repair and waterproofing business we are always amazed this has never been included. John McEwen from Eastern Ontario Foundation has fought for years to get this included, as have many other reputable contractors, it is a regional responsibility. In my local area, the City of Kingston does not require a permit, yet the township just north of the city does, go figure! The CBO for the individual municipality can mandate this re-quirement and some do. If you are at the stage where this type of work has been recommended for your basement, check with your municipality to see if they require a permit. This can be a very expensive repair job; you should do your homework, check references and talk to neighbours and friends who have had the same problem. Ask them who fixed their basement and were they satisfied. Responsible, reputable foundation contractors are few and far between and the good ones are usually booked weeks and months ahead. The Pro’s have a recognized process and we are going to go thru this step by step so you understand what should be done. I have been on site with Jerry Shea, the patriarch of Shea Construction in Kingston on different occasions. Jerry has many, many years of foundation repair experience to support his company.

6

Waterproofing continued

We Excavate

The first thing that Jerry does is walk around the building, establish the grades and what he thinks may be the ground water issues. I was at a home recently that has a water issue in the basement, Jerry calmly described how a nearby ground water drainage pipe that was installed in the 50’s had plugged years ago, this is where experience counts. He knew where the water would pond in the yard before the owner could describe it. He then goes to the basement and brings out his moisture meter, meticulously checking numer-ous spots on the wall for moisture. He takes his time

explaining the issues to the client, what it will take to fix the problem and how much it will cost. I have seen Jerry talk to a client for more than an hour explaining what has happened and why. I know two other contrac-tors in this business that operate the same way, the Pro’s have a responsible dedicated method, they know this is going to be an expensive repair and want you to understand the process. Once you have decided to “dig it up”, don’t expect the

back hoe to arrive and start moving dirt the next day.

We Excavate

Excavation

Your contractor has some homework to do. His first call will be

to the local utilities company to establish where the under-

ground residential infrastructure is located. Everything is under-

ground today in many cases. Your hydro, water, gas and sewer

lines must all be located. If there are overhead wires that could

cause equipment issues the appropriate utility company should

be advised and if necessary have the lines temporarily moved.

If your home is located in a high traffic area a traffic control

plan should be established. Most reputable contractors have a

strong working relationship with the municipality; they realize

they must work together here. In some cases they may be

aware of an underground tank and this must be attended to

and removed first, especially if it is an abandoned oil or fuel

tank. If the neighbors are close by most reputable contractors

will contact them and advise them of pending work and the

proposed schedule to help reduce any inconvenience.

Preparation of the outside of the home is established, if you

have a favorite tree, tell your contractor so they are extra care-

ful. Equipment like your air conditioner will have to be moved

by a reputable TSSA contractor, steps and decks can sometimes

be moved and replaced, other’s may need to be demolished.

Your contractor should establish all of this before a shovel hits

the ground. I have seen the Excavation Assessment and Proce-

dures list that Shea’s use and it’s impressive. It covers every-

thing from safety, traffic control, and local hazards to necessary

equipment that will be need on site. Most good contractors

operate with similar job site records.

8 Excavating the foundation

The Dig Begins

Last week we listed off the procedures that are needed to properly prepare a site for

excavation around a block basement, in previous weeks we discussed waterproofing

methods and reasons why block basements are known for water issues.

There are a number of advantages to digging up a basement and certainly benefits

from insulating the exterior of the foundation. Some of the companies that manufac-

ture waterproofing coatings and membranes actually require an insulation barrier

applied to the wall after covering is installed. This is done to protect the waterproof

barrier from damage by soil or rocks when the back fill work is done. While it is not

required, unless it’s a manufacturer’s standard, exterior insulation applied to the

foundation is not as common as it

should be. There is the cost factor here

and often times the five figure excava-

tion “hit” on the family budget is

enough that the additional two or

three thousand for rigid foam insula-

tion is beyond available funds. Install-

ing rigid foam insulation will dramati-

cally reduce the level of condensation

in the block walls. It might mean a va-

por barrier on the interior wall may not

be needed. It protects the walls from

additional air leakage provided this

insulation application is installed up the

wall fully including the rim joist or

header areas, whichever term you like.

This insulation will dramatically im-

prove the air quality and temperature

in the basement.

“I won the bet”

A couple of years ago I was on a

major renovation and basement

excavation site and the owner was

hesitating on the cost of the insula-

tion. I took him inside and we took

the temperature of the home’s

main level by using a laser ther-

mometer. We then went to the

unfinished basement and there

was a seven degree difference. I

told him that properly installing

the external rigid foam and includ-

ing the rim joists would close this

gap by around 50%. He bet me a

steak dinner I was going to be

wrong….I enjoyed the dinner….his

basement was 2 degree different

from the main level when the job

was done.

“I told him that properly installing the external rigid foam and including the rim joists would close this gap by around 50%..”

The Dig

9

Caption describing picture or graphic

Now on to the dig and everything was getting ready, I joined Corey Shea from Shea’s Construction on the site. He is the field

boss and one of Jerry Shea’s Sons. Corey was carefully going thru their Excavation Assessment as their crew unloaded the

track hoe. I was pleased to see the size of equipment on site. Some years ago I had a block wall fail because we allowed a full

sized back hoe too close to the block wall. They had put up the stakes for the safety fence and the operator slowly began at

the edge of the foundation removing the soil and piling it away from what became the hole beside the foundation. Large rocks

and any hard clay pieces were separated and removed from the stored soil. Corey said they will use the existing soil provided

it is suitable, if not they replace it with better draining soil. If present, they also removed the old clay drainage tile. Some

homes built before the 80’s when “Big O” came into popularity had a clay tile drain system installed around the foundation.

Corey stated that nearly 100% of those that they dig up are filled with silt and roots, long since failed in their usefulness. All of

this waste is removed from the site.

Once the trench is dug they care-

fully shore up the walls with braces

and plywood to protect their staff.

Corey was adamant at this point

about the crew’s safety in the

trench and watched over this instal-

lation carefully. They now began the

arduous task of scraping down the

walls and checking for any major

cracks or openings in the founda-

tion. Depending upon the severity

of the cracks they use professional

crack sealants or a prep coat and a

mesh type covering that is imbed-

ded into the prep coat. Corey said

each job is different and they come

prepared for different crack and

patch work. The time consuming

work of preparing the walls by

scrapping them down, pressure

washing if necessary and removing

any old parge that is still present

that would be below grade. At this

point they try and establish where

the drain tile will discharge. Corey

said this can be frustrating at times

as many homes never had a proper

discharge to the storm sewers or a

dry well.

Once everything is prepared and

the trench cleaned out the clear stone is brought in. A layer is set at the edge of the foundation to “bed down” the perforated

plastic pipe that will become the drain tile. Corey said this is one of the most important areas, ensuring that it sits beside the

footings and has a proper base for drainage. Shea’s have a policy of adding close to three feet of gravel from the base up the

wall. Corey recognized this may be “over kill” but they feel the extra cost is outweighed by the benefits of proper drainage.

Second Choice

External pumps are not as

common, I know of only

one basement contractor

who uses this installation. I

have seen these used

where the basement is oc-

cupied and the owner

wants access to the pump

at any time. The contractor

must excavate a pit about

20 inches below the foot-

ings, usually in a corner.

They will install a culvert

section as a chamber for

the sump pump. Care must

be taken to ensure the

pump and float is not ob-

structed. The rigid plastic

line should be discharged

on the surface. In this type

of installation you do not

use a check valve; the cover

should be secure, water

resistant and insulated to

reduce the chance of

freezing.

The Final Step

The last step depends upon the water test that they do on the drain tile. If the water

test shows good discharge or they know they have got a storm sewer hookup, then a

sump may not be necessary. Corey Shea noted that a high percentage of basement

waterproofing jobs they do includes a sump pump if they are the least bit unsure of

the drainage. There are two methods of installing a sump pump, internal or external.

Corey commented that they prefer the internal pump for a couple of reasons. He has

seen the external units freeze up if they are poorly installed and if a pump fails this is

Last week we got the block foundation

walls cleaned, covered in a waterproof

coating and reset the drainage tiles, then

installed a bed of washed stone. The

stone acts as the clear base for the soil

that will back fill against the house. Prop-

erly draining soil is the last step and can

consume a large portion of the actual

budget if it has to be removed and re-

placed. The soil that goes back into the

hole has to be pushed in carefully; too

much pressure can crack or bow the

wall. I have seen a basement contractor

do this in layers and slowly raise each

level of soil. Once the trench is filled the

soil should be set with an aggressive

slope away from the building. This allows

for the expected settlement. Casey Shea

made comment during this interview

that they go back to a site some weeks

later and check to see if the soil has set-

tled more than expected and they have

brought in additional soil in some cases

so this all important drainage away from

the building is maintained. They seed it

down for grass and replaced the shrubs

if requested.

10

Sumps

Excavate outside the house to confirm the existence and shape of the tile system

Dig a hole through the floor slab down about 45cm (17 1/2 “) on the opposite side of the wall inside the basement

Dig a tunnel under the footing connecting the two

Have the tiles empty directly into the sump pit

Allow water under the floor slab free access to the pit

If using manufactured plastic “pails” as sump pits, make sure they have enough access holes punched or drilled into them

Secure a sump pump into the pit and direct discharge water in a legal fashion (do not flush water directly into septic tank)

Securely cover the pit

Backfill exterior hole with as much clear stone as possible

To avoid soil gases, sumps should be covered and vented outdoors

When they know they need a sump pump they jack ham-

mer out a spot in the basement floor, usually at a corner

where they can loop in the drainage tile. Most pro’s use the

manufactured plastic bucket designed for a sump installa-

tion. These buckets are about 18 inches deep and are usu-

ally set up on a base of washed gravel. A channel is dug

under the footings to allow the plastic drain pipe to be dis-

charged into the bucket. There are a number of punch out

holes that can be opened to help with the under pad drain-

age too. Shea’s use a submersible sump pump manufac-

tured by Hydramatic. I have also used this brand; they are

known for long term reliability and are far better than the

stem style of sump pump. Once this is all set in place a hard

plastic discharge line should be installed along with a check

valve fitted just above the base of the liner. This check valve

stops the back flow of water reversing the pump; this will

reduce its life span. Once outside the wall with the hard

pipe you must carefully discharge this water, it can create

some amount of erosion. If you are in the city you cannot

discharge this water onto your neighbour’s property. It may

take some thought, don’t bury this line however. I have

seen more than one early spring thaw where the under-

ground pipe froze and caused some considerable damage

when the final spring thaw came.

Back inside the home this sump pit should be finished.

Proper concrete poured around the top edge and the

bucket cover fitted and twist locked into place. This is done

for a couple of reasons. It helps reduce the evaporation of

the water into the basement which only adds to extra hu-

midity and the cover stops anything from falling into the

sump hole and damaging the actual pump. If at all possible

the pump should be on a designated electrical circuit so

that no other tools or appliances could accidentally trip the

power supply.

ALLTECH CONSULTING GROUP

A tip of the hat to John McEwen who co-authored the CMHC booklet “A

Guide to Fixing Your Damp Basement”. It’s an excellent book.

A special “Thank You” to the Shea Family; Jerry, Casey, Corey and their staff

at Shea Construction in Kingston Ontario. They opened up their job sites, al-

lowed me access to their work plans, operational procedures and were pa-

tient with my questions. Without them this series on block basements would

not have been possible.

Many Thanks

Cam Allen L.I.W. RHI

Phone: 613-546-9876

cam@alltechconsultinggroup.com