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Photograph of a concrete slab control joint Seal or Repair Cracks in Concrete Floors & Walls

  • POST a QUESTION or COMMENT about sealing floor or foundation or wall cracks, water entry through cracks, crack sealing approaches, costs, reliability

How to seal cracks in concrete floors, foundations, walls, or other masonry: this article how to seal and repair of cracks in poured concrete slabs, floors, or walls.

We list all of the current methods used to seal control joints or cracks that occur in those building surfaces, giving the properties, general procedure, and pros and cons of each method: control joint inserts, masonry caulks, radon crack sealants, semi rigid epoxy resin crack fillers, special poly urea caulks designed as a joint filler - polyurethane foam injection to seal cracks, grouts including portland cement, latex-modified, epoxy, modified epoxy-supported, and furan grouts or other products used to fill or seal cracks in concrete or other masonry surfaces & structures.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

How to seal control joint & expansion joint cracks in concrete slabs

Photograph of a sketch of typical crack patterns in a poured concrete slabHere we discuss how to choose among and apply the alternative methods for repairing or sealing cracks in masonry surfaces such as poured concrete floor slabs, concrete foundation walls, or brick or masonry block foundation walls. We describe use of epoxy sealants, polyurethane foam sealants, and hydraulic cement crack repair sealants.

This article series describes how to recognize and diagnose various types of foundation failure or damage, such as foundation cracks, masonry foundation crack patterns, and moving, leaning, bulging, or bowing building foundation walls.

Types of foundation cracks, crack patterns, differences in the meaning of cracks in different foundation materials, site conditions, building history, and other evidence of building movement and damage are described to assist in recognizing foundation defects and to help the inspector separate cosmetic or low-risk conditions from those likely to be important and potentially costly to repair.

Here we discuss: a list of materials used to fill poured concrete slab control joints. How to seal a cracked masonry foundation wall or floor slab. Typical concrete crack preparation for sealant with an epoxy product.

Use of Polyurea as a control joint filler or crack sealant in concrete slabs (Polyurethane Foam Injection Method). Use of Epoxy-supported Grouts as a control joint or crack filler in concrete slabs or walls.

List of the Types of Tile Grouts, their Bonding Agents and other Properties. Concrete expansion joint sealant products, epoxies, caulks.

Use of Hydraulic Cement for Repairs in Concrete Slabs, Foundations, or Masonry Block/Brick Walls.

When should we not seal a foundation wall or floor slab crack?

Iron suffide pyrrhotite cracks in a Connecticut Founation (C) CCAB & Inspectapedia.comWarning: some crack sealing operations may make crack diagnosis or monitoring more difficult

Watch out: First of all do not just seal a crack if the crack size, shape, pattern, location, or other evidence indicate that something important is going on with the foundation. Further evaluation and choice of proper repair method may be in order.

If for example we think that there may be active foundation movement or settlement going on and if that condition is going to be monitored for evidence of further movement, just pushing a flexible sealant or caulk into a crack is leaves some worries unattended:

This photograph of foundation cracks attributed to concrete that included iron sulfide (pyrrhotite), provided courtesy of CCACB - Connecticut Coalition Against Crumbling Basements. The pattern looks like shrinkage but the crack width is larger than normal shrinkage cracking.

Watch out: before sealing concrete cracks like those at page top be sure that you've got a credible diagnosis of their cause. This cracking pattern could be due to iron sulfide pyrrhotite cracking damage from inclusions in the original concrete as mixed and placed.

See FOUNDATION DAMAGE by MATERIAL or INCLUSIONS for details.

We may decide to seal a cracked wall or floor slab anyway, to try to reduce water entry in a building, but remember the implications of sealing we've just listed.

Types of Sealant Repairs in Concrete & Concrete Structures

Control joint sealant:

control joints, designed to control where cracks appear in concrete placed horizontally or vertically, are themselves are sealed against water, frost, debris and to handle recurrent movement (listed below) using a flexible sealant.

Recurrent movement:

Seal and repair cracks in concrete using injection of either epoxy resin or polyurethane where recurrent movement is expected (in my opinion a flexible sealant is what's called for here) when the movement is considered normal, perhaps caused by traffic vibration or temperature swings, and where the movement is not threatening structural damage.

Stop a water leak:

Seal and repair cracks in concrete when it is important to quickly stop water leaking through a crack,seal those cracks in concrete using injection of either epoxy resin or polyurethane sealant.

Structural repair:

Seal and repair structural cracks: for some situations (usually where an engineer, expert in masonry repair has made an assessment), actual structural repairs are made using injectable epoxy resin and possibly in some (probably low-load) cases by using injectable polyurethane sealant.

In my opinion (I'm not a P.E.) this application of injected epoxy resin is probably most-appropriate when cracks have appeared due to non-recurrent stresses. When we epoxy cracked structural concrete or a concrete slab that was broken by an initial installation error or by a subsequent event, we expect the repaired area to be as strong or stronger than if no crack were present.

Structural reinforcement:

some sealant manufacturers such as Sika provide seal or wrap-and-seal systems that actually provide additional strength to existing concrete structures such as concrete columns.

Structural reinforcing wrap systems may include use of synthetic fabrics, carbon fibre fabrics, and other wraps. These products might also be used on steel or concrete that has been damaged by weather, frost, corrosion.

Surface repair:

for working surfaces such as industrial work floors or parking decks cracked by spider-webbed shrinkage cracks that are non-structural, special "healer-sealer" crack sealants may be applied.

Specialty Epoxy Resin and Structural Engineering Systems for Concrete

The situations listed above are those of most-interest to owners of residential and smaller commercial buildings. Below are examples of additional applications of epoxy resins and sealants in construction:

Anchoring epoxy products:

used to inject into holes into which connectors such as bolts or post anchors will be placed.

Bonding agent epoxies: used to promote secure bonding between abutting, often different materials. A special example is the use of segmental bridge adhesives that bond post-tension pre-cast concrete bridge segments to other structural members or to one another.

Epoxy resin adhesives are formulated for bonding concrete to concrete, concrete to other masonry, concrete to steel, and concrete to wood or to other substances.

Overlay epoxy resin coatings:

used as a coating on concrete surfaces for skid protection or for patching damaged surface areas. Some of these epoxy resin products are formulated for use as a high-friction surface or for use to repair spalled or chipped concrete surfaces.

Special acknowledgment: some of this discussion was informed by reviewing products and engineering literature provided by

How to seal a cracked masonry foundation wall or floor slab

To seal a shrinkage crack or a control joint crack in a poured concrete slab, regardless of whether or not it has occurred at an expansion or control joint, it may be appropriate to seal the surface to resist water entry and radon gas entry.

Control joints are also sealed to provide a smooth and clean concrete surface which does not collect surface moisture or debris. Keeping surface water from entering at a control joint might in some cases also help avoid uneven soil settlement below the slab and tipped or heaved slab sections.

To seal a control joint or expansion joint crack in a concrete slab use a flexible sealant designed for foundation crack repair or sealing. The radon mitigation industry offers special foundation caulks and sealants for that purpose as well. (If water is coming up through a concrete floor or slab, sealing cracks is probably not going to be enough - you need to address the cause of water below the floor.)

List of Types of Materials Used to Fill or Seal Poured Concrete Slab Control Joints

Goodbye Crack Filler at InspectApedia.com

Any sealant that is going to be used to fill a control joint in a slab needs to have the ability to bond to the sides of the cut or opening of the joint, to remain flexible over temperature and moisture changes, and to withstand both compression and expansion as the concrete moves in response to curing and in response to temperature and moisture changes.

Epoxy, for example, is not generally used to fill the expansion joint in newly-poured concrete because the concrete is just too wet and has too much movement for the epoxy to bond and perform acceptably. Similarly, a special product would be needed to fill a control joint in concrete in very cold weather.

Watch out: select the right product for your application. Some crack fillers like the spray injection product Good-Bye Cracks elastic crack "cover" product shown in our photo are not suitable for concrete.

The manufacturer says this product can be used to fill cracks in plaster, drywall, and wood and that it dries to a flexible, paintable finish.

Typical concrete crack preparation for sealant with an epoxy product

Concrete crack patching methods (C) Carson Dunlop Associates Carson Dunlop Associates ' sketch shows three common methods used to seal cracks in masonry walls in an effort to stop foundation leaks.

[Click to enlarge any image]

  1. Cleaning a concrete crack for patching and sealing:

    The crack or expansion joint must be cleaned of all debris; power washing and vacuuming may work but inspect the crack or joint to be sure it is clean along its entire length.

    Otherwise the sealant may fail to adhere and the crack will leak. Wire-brushing or chipping the crack sides is not normally required when using an epoxy sealant.

    (Traditional concrete or masonry patching (and plaster repairs), on the other hand, was traditionally applied after cracks were chipped and widened into an inverted "vee" shape to help keep the patch material in the crack.)
  2. Mix the epoxy sealant 

    according to the manufacturer's directions.

    Some low volume epoxy sealants are supplied in a dispenser which mixes the two parts together in the proper ratio automatically during dispensing from a tube (see your dentist for an example.) Other crack sealants such as prepared caulks, may come pre-mixed in a tube.
  3. Install the backer rod 

    specified by the sealer manufacturer if you are sealing an expansion joint.

    The backer rod provides a flexible filler that keeps the sealant in the joint during curing and also reduces the total volume of concrete crack sealer epoxy needed.

    We recommend using backer rods also if sealing wide cracks in concrete walls or floors, but first you need to have those cracks evaluated to determine the cause as other important structural repairs could be needed first.
  4. Sand

     (clean, dry) may be used as a filler for cracks - an easier approach if you are repairing an irregular crack in a floor. Sand should stop about 3/4" from the top of the floor surface to give adequate volume of sealer epoxy in the crack.
  5. Epoxy crack patch cure time:

    Keep traffic off of the sealed crack until the sealant has cured.

    Typically a thin film will form on a crack filler epoxy in 8 hours, the sealant will be hard enough to withstand traffic in 24 hours, and it will fully cure in about a week.

These notes are based on epoxy product application information available from Lone Star Epoxies.

Use of Polyurea as a control joint filler or crack sealant in concrete slabs (Polyurethane Foam Injection Method)

Wall crack repair by polyurea injection (C) Carson Dunlop Associates

Polyurea joint filler products for concrete control joints have received attention for filling concrete control joints and is increasingly used in that application since this material is resistant to moisture, has high adhesion properties when used with concrete, and will cure in very cold weather.

Polyurea sealant products are also reported to be useful in sealing control joints in "green" concrete which has not yet had its full 28 day period of initial curing.

An advantage of polyurea or polyurethane used as a crack sealant is that the flexibility of the material will accommodate slight seasonal or temperature-related movement that might otherwise cause new cracks in an epoxy-repaired structure or reopening of repaired cracks in a mortar or concrete-repaired crack.

Also in our experience, because the injected polyurethane foam expands after it is injected into a crack, you may find it easier to fill the crack through the building floor slab or wall than when using alternative repair methods such as epoxy or masonry repair kits.

Carson Dunlop Associates' sketch (left) illustrates foundation wall crack repair using epoxy or polyurethane injection.

List of materials, product sources, how-to for polyurethane foam crack sealant

Use of Epoxy-supported Grouts as a control joint or crack filler in concrete slabs or walls

Epoxy grouts are available which can be mixed and troweled into a concrete crack or joint. These products are less flexible than the control joint fillers described above. In our opinion, an epoxy grout filler may work fine to provide a well-bonded repair to a stable wall or floor crack in an area where there is no anticipated further movement such as from temperature or moisture variations.

Watch out: while epoxy, a material stronger than concrete alone, is sometimes used for structural repairs, if your building masonry (concrete, brick, masonry block) is cracking due to ongoing movement, settlement, frost, or other active or recurrent problems, unless those conditions are fixed, sealing a crack with epoxy will not prevent new cracks from forming.

But read the manufacturer's intended application before buying an epoxy reinforced grout for building crack repair. Do not use the product where it was not intended unless a call to the manufacturer provides you with good information that it's acceptable to do so.

On the one hand we like using a rigid material to fix a supposedly stable crack in a residential building since the fact that the patch is inelastic means it will be easy to see if there is ongoing or new building movement.

On the other hand, a small amount of moment in a foundation wall or floor slab due to changes in temperature will leave a flexible crack filler undamaged and sealed where a rigid material may fail.

List & Sources of Epoxy Grout Products & Structural Injection Concrete Repair Products

Use of Peel-and Stick Surface Sealant Kits for Epoxy-Repair Cracks in Concrete Walls

For building surfaces that will remain exposed and where cosmetic appearance is a concern, RadonSeal (and perhaps others) offers a stick-on injection port system that allows the crack material to be injected into a wall or floor crack to leave a smooth surface even with the existing wall or floor surfaces on either side of the crack.

RadonSeal's Easy-Peel Sealer kit uses a surface seal that includes injection ports. After the injected sealant has cured, the surface seal and injection ports are peeled away from the repaired surface.

Quoting: RadonSeal Crack Seal and Port Adhesive 1:1 is a high modulus epoxy gel designed for surface sealing of cracks prior to injection and for attaching surface ports. It can also be used for bonding miscellaneous materials to concrete.As with any epoxy adhesive, surface preparation is critical.

Concrete surfaces should be cleaned by wire brushing or other mechanical means. All loose or unsound material must be removed. Surfaces should be dry and dust free to insure a superior bond. Application onto wet surfaces is not recommended.

How to Choose Between Using an Epoxy Crack Sealant & a Polyurethane Crack Sealant

High Pressure or Low Pressure Slab or Foundation Wall Crack Sealant Injection

Most foundation wall and floor slab cracks can be successfully filled and sealed using low-pressure injection such as that afforded by a caulking gun and cartridge of sealant, or similar device for both epoxy and polyurethane foam sealants.

Professional polyurethane foam injection crack sealing applicators may use a high-pressure injection system using equipment that includes a pump or a device similar to an automotive grease gun and pressures up to 250 psi. Drilling to prepare injection ports along the crack may be required.

Reasons to use an epoxy-based crack repair or sealant method

Reasons to use a polyurethane foam injection crack sealant

Use of Hydraulic Cement for Repairs in Concrete Slabs, Foundations, or Masonry Block/Brick Walls

Hydraulic cement used for crack repairs is a waterproof cement product that is sold dry and mixed with water on the job to prepare a slurry that is painted (or troweled) over a crack in a foundation wall or in some cases (DryLok or UGL foundation wall sealants) painted over the wall surface in a paint mixture.

Hydraulic cement is often lower in cost than the epoxy and polyurethane products described here. However, the repair is at risk of re-cracking due to product shrinkage or due to even slight movements in the structure from settlement, earth or frost pressures, or thermal changes.

A principal advantage of hydraulic cement for repairing & sealing cracks in masonry floors or walls is that it can handle and effectively seal a crack even when there is significant active water leakage through the crack. The cement, properly mixed (as stiff as possible) cures and expands to seal the crack in the presence of water.

[As early as 1969 we used this approach to successfully seal holes in a masonry block foundation wall through which groundwater was squirting several feet into the basement. We mixed a plug of hydraulic cement and forced it into and against each hole until it set firmly enough to remain in place - about 3 minutes. - Ed.]

Watch out: any cement product is caustic and can cause skin burns or eye or lung damage if you do not handle it properly and wear the proper protective gear for eyes, lungs, skin.

For an effective repair of a wall or floor crack using hydraulic cement you will need to clean out and widen the crack to approximately 1" wide x 1-1/2" deep, ideally with the crack wider at its innermost and more narrow at the wall or floor surface (a "V" shape) to give a mechanical bond to the cured concrete patch.

For a wall crack through which water is seeping, seal the crack progressively beginning at its highest point on the building wall. When all of the crack has been sealed except a single pressure relief point, that final leak is sealed with a molded plug of cement.

List of the Types of Tile Grouts, their Bonding Agents and other Properties

Questions and answers about sealing floor cracks in Slabs

Question: should we seal floor cracks exposed when we pulled up basement carpeting? Our house had a radon problem

We have had our home mitigated for radon. The latest reading is 2.9. Therefore, we feel we are controlling the radon successfully. We are in the process of removing carpet from a 8' X 12" bathroom in the basement. In preparation for installing an overlay linoleum we found a irregular crack in the concrete floor.

Our question is - should we seal this crack with some time of sealer that could be painted on and would this be effective? If so, what type of product would you recommend? - F.H.

Reply: In general, sealing exposed floor slab cracks is a good idea where there was a radon concern, though if your mitigation system is working it might not be critical.

Hairline concrete slab cracks © Daniel Friedman at InspectApedia.com

A competent onsite inspection by an expert might find other cracks, openings, or sources for radon gas leakage that you'd want to address, but usually that would have been done when your radon mitigation system was installed.

Following the installation of a radon mitigation system the installer is expected to make a follow-up radon gas level measurement to be sure that the mitigation is working as expected, and s/he also inspects the home to see if you have exhaust fans or other features that could accidentally interfere with proper operation of the radon mitigation system itself.

If all of that was done, the added radon gas leakage into your home from pulling up carpet to expose a floor crack should not be significant.

Redguard Seam Tape from Custom Building Products, uncouples concrete or wood subfloor cracks from finished ceramic, tile, slate or stone finish floroing - described in detail at InspectApedia.comNevertheless it would be good practice to seal any floor slab cracks that you expose.

Here are some things to consider:

If your floor slab cracks are hairline (less than 1/8" across - see our photograph above left) they may be normal concrete shrinkage and they may be too fine to seal with a polyurethane sealant (see our polyurethane sealant link below).

In that case a sealant paint or a combination of mesh tape and sealant used to cover cracks in concrete before installing tile would still work well.

Particularly where ceramic tile is to be installed on a slab we want to protect against telegraphing of slab cracks up through (and breaking) the tile.

See details at TILE ISOLATION MEMBRANES where we discuss Custom Building Products' RedGuard Uncoupling Mat & Uncoupling Crack Isolation Seam Tape and membranes (shown above) and other Concrete Slab Crack Suppression and Isolation Joint Tape products.

and also see FLOOR TILE INSTALL on CONCRETE.

For larger floor slab cracks (such as shown in our photo below) there are some sealants ("caulks") widely used by radon mitigators that work well in floor or wall cracks, typically polyurethanes. The crack is vacuumed or cleaned, and when dry, sealed.

Concrete slab crack © Daniel Friedman at InspectApedia.com

More sophisticated floor slab crack sealing is done if you are going to put down ceramic tile: the repair includes a strengthening mesh glued to the floor over the crack to resist the transmission of the crack upwards through the ceramic tiles. Under carpet you don't need that step.

At CONCRETE SLAB CRACK REPAIR

and SEAL CRACKS by POLYURETHANE FOAM INJECTION at we discuss methods to seal cracks in floors.

At HOW to REMOVE INDOOR RADON we include more details on how to get the radon level down in homes. You'll see that sealing and caulking to stop radon gas from entering at floor or wall cracks or joints is important.

While you're at it, don't forget to check for gaps that may have opened between the floor slab and the foundation wall - seal those too.

...


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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2023-09-21 by InspectApedia DF (mod) - Where to buy epoxy resin brick repair kit

@S. Monks,

Dap, Gorilla Glue, and many other companies offer repair epoxy products for masonry including brick walls. If you do a simple web search for

Epoxy for masonry repair

You'll be deluded with products.

While repair epoxies can be extremely strong. I think I see in your photo a thin vertical crack that extends over several feet and possibly over the entire wall. Photo doesn't give enough details and know it the extent of the crack. But a vertical crack in a masonry wall needs some diagnosis before you attempt to repair.

For example if the foundation is settling then there will continue to be ongoing movement until the footing or foundation problem is corrected.

Read more about brick repair at

BRICK WALL DAMAGE REPAIR
https://inspectapedia.com/structure/Brick_Wall_Repairs.php

Let us know if you have additional questions.

On 2023-09-21 by S. Monks

Where to buy epoxy resin brick repair kit

cracks in brick wall (C) InspectApedia.com SMonks

On 2023-07-01 by InspectApedia Publisher - is crack filler enough to repair crack in concrete porch

@Alma,

For a side-porch with a concrete floor that's 4 feet above ground with a bricked-in perimeter I'll bet you a 6-pack of Castle Danger Beer that the builder filled the brick surround with dirt and poured a slab on it.

If that's how the porch was built, and IF the surrounding foundation wall is indeed supporting the porch slab and is itself not damaged, then most-likely settlement combined with inadequate re-bar in the concrete and inadequate connection of reinforced slab to a supporting foundation wall explain the cracking.

Using a crack filler is not going to fix this problem.

I'd remove enough concrete to see what's under the slab - post a photo of what you find and that'll tell us how to proceed.

Also post a photo (one per comment) of the ground and supporting brick wall along the porch side where this floor crack has appeared.

On 2023-07-01 by Alma

This is the floor of my concrete porch 25 feet long and 4 feet wide. The house was built in 1968. The porch is about 4 feet off the ground and bricked in. Could I still use a filler or do I need to have whole thing pulled up and redone?

crack in concrete (C) InspectApedia.com Alma

...

crack in concrete (C) InspectApedia.com Alma

...

crack in concrete (C) InspectApedia.com Alma

On 2023-05-28 by InspectApedia DF (mod) - what type of cracks need "patching" or "epoxy injection" for concrete basement walls?

@Damian,

To answer the question, you have to look at the crack itself to determine the material, the cause of the cracking, and essentially determine whether the crack is a structural problem or just an opening that you need to seal against water or air leaks.

There are structural epoxies that engineers sometimes specify for repairing structural cracks in concrete; you would not use a foam or silicone or similar sealant in such cases.

For just sealing water or air leaks you might use a masonry patching compound or even a crack sealing foam or other sealant.

But, in my OPINION [DF] it is really important to first diagnose

- the cause of the cracking - we may need to fix the cause rather than just seal the crack - lest the problem continue

- the effect of the crack on the rest of the structure - have building components or supports moved ?

On 2023-05-28 by Damian

How do you determine what type of cracks need "patching" or "epoxy injection" for concrete basement walls?

On 2021-12-07 by Inspectapedia Com Moderator

@Round Rock Concrete Services,

Thank you.

We've worked hard on this material for decades, so are really grateful when a reader finds it useful and trustworthy.

We also welcome your photos, questions, criticism or suggestions.

On 2021-12-07 by Round Rock Concrete Services

This is very helpful!!! Keep on sharing. Thank you!

On 2021-11-23 by Inspectapedia Com Moderator - Can I repair cracked masonry when it is damp and moss protruding from the crack?

@Carmen,

Yes but no.

You can use most masonry patch products on damp masonry, in fact often that's a better approach,

but if you don't first remove the moss and clean the surfaces your repair won't last long.

On 2021-11-23 by Carmen

Can I repair cracked masonry when it is damp and moss protruding from the crack? Or is it better to wait for it to dry out?

On 2021-08-18 by inspectapedia.com.moderator - What is the best way to fill in a cracked foundation concrete slab edge

@Teresa,

From your photo I'm not clear what we're seeing nor do we know the details of your concrete floor and heating system design.

But in general:

PEX radiant floor slab heating tubes must be high in the slab - say in the top 2 inches - otherwise your radiant heat floor will be a disaster - as you can read at

RADIANT HEAT MISTAKES

So we hope your contractor didn't bury the tubing deep into the slab.

For filling a chipped slab edge like that in your photo any simple concrete patching compound can work, though I might consider a good-flowing polyurethane sealant as an alternative.

On 2021-08-18 by Teresa

What is the best way to fill in a cracked foundation concrete slab edge and who should do it - a trade which poured the slab, or flooring contractor?
The concrete slab needed to be build up higher than the EPS foundation walls since Pex radiant tubes were installed high and in order to protect them slab layer needed to be higher.

cracks on edge of concrete slab (C) InspectApedia.com Teresa

On 2020-06-23 by danjoefriedman (mod) - might be shrinkage cracks in what may be a stucco exterior

I can't say with so little info, Carlos but you may be seeing shrinkage cracks in what may be a stucco exterior. The issue ranges from cosmetic to more serious if those cracks invite leaks into the walls. Just adding more cement may not be the answer if the wall system lacks needed control joints.

On 2020-06-23 by Carlos

I just had a add on room built they put cement on exterior walls I see alot of cracks is that normal or do they need to add more cement for a finish product

On 2020-04-22 - by (mod) - Engineer says use epoxy sealant, foundation repair companies all say need steel reinforcement

Photograph of our sketch of a simple way to use a plumb line and measuring tape to determine the amount of lean or bulge in a foundation wall © Daniel Friedman at InspectApedia.comJoseph

While normally I trust the opinion of a licensed professional engineer as authoritative, there are some concerns here.

A sealant or epoxy is obviously appealing as it is far less troublesome and costly than foundation repairs that require insertion of structural steel reinforcement, pilasters, or even re-building of a wall.

But such a repair is more-likely to be appropriate when the amount of cracking is minor and where there is no significant inwards bulge of a wall.

Your comment is posted on our article on using sealants and repair epoxies on a CONCRETE foundation wall or floor slab.

Sealing a crack that's leaking through a wall or floor is likely to be a very different problem than repairing a structural foundation wall that is damaged, moving, displaced.

Without answering at least a few basic questions we cannot assess the suitability of a foundation repair proposal.

What are the nature of, extent (not just crack length but width, displacement, etc), and cause of your foundation damage?

At a national conference I hosted on this topic we polled a room full of over 100 engineers and home inspectors and foundation repair contractors.

The predominant opinion was that more than an inch of inwards bulge or lean or displacement in a concrete block foundation wall was considered serious and in need of more than a band-aid or superficial repair.

Your engineer may have already considered everything and she may operate with a style that prefers to "just give the customer the answer" rather than explaining anything at all. We often see this among credentialed experts such as engineers, architects, and doctors.

But when the patient or customer is uncertain, nervous, or hearing conflicting advice, some willingness to explain, in plain language, is needed.

1. is your engineer actually expert and personally experienced in residential foundation damage cause, failure, and repair?

Often a P.E. may be ethical, savvy, smart, but may have expertise in a different area from the one in which you've got comments. An engineer isn't supposed to practice engineering out of their area of education and certification, but I've certainly seen exceptions.

(A well-known engineer in Long Island NY was trained as an aerospace engineer who later decided to open a home inspection company. He admitted privately that at inception he knew nothing about residential construction.)

While there are some structural epoxies used in some concrete damage repairs, they are not, in my experience, applied to a residential block foundation wall with horizontal cracking, bulging, buckling. Example questions (this is not the full list):

Really? The up-side of trying a repair epoxy is that it's cheap, quick, and ***IF*** there is not already substantial foundation movement then you might live with a "watch and see" attitude for a few years.

Watch out: a 20 foot crack in a foundation wall joined by a six-foot crack in an abutting wall sounds as if there may be an underlying cause of settlement or foundation movement. Some diagnosis of the cause, the effect on the structure, and the extent of movement are needed to support the choice of foundation repair action.

Your engineer and your foundation repair companies may have considered this but I don't hear it in your question.

2. What about the foundation repair company?

I tend to trust the opinion of a foundation repair company who has inspected, repaired, or otherwise rebuilt a very large number of buckled or bulged block wall foundations.

But ALL of what I'm saying is arm-waving speculation as I don't know much your specific foundation.

You might want to take a look

at FOUNDATION DAMAGE SEVERITY

and

BULGE or LEAN MEASUREMENTS

On 2020-04-22 by joseph rene connell

I have a engineer,s report stating my horizontal basement wall crack is not structual and requirers Sika epoxy 3001 injection.I have had several companies come in and they all say I need steel.

The crack is about 20 feet on one wall and 6 feet on the attached wall. the walls are poured concrete. We have had the engineer over twice and same result even when I asked him if i needed steel

On 2019-12-12 - by (mod) - tips on how to seal/repair cracks in concrete floors & walls.

Evan Oakes said:

Thanks for the tips on how to seal/repair cracks in concrete floors & walls. On my side here I used hartfordepoxyflooring com epoxy concrete repair on my cracks on floors,

Once you epoxy patch has cured properly according to instructions, clean the floor again to remove any dirt and oil, then buff the floor with an 80-grit sanding screen. Vacuum and wipe the floor to remove any dust and apply the epoxy paint. This must cure for 12 to 24 hours, then you can apply a clear epoxy finish. Thanks for your tips.

On 2019-12-09 - Mike Smith said: -

I appreciate you posting about this. Just the other day, a bad storm came rolling through my neighborhood, and it turned out that I leaked into my basement walls. Because of this, my whole basement got flooded.

I like that part where you talked about repairing the damage especially. This is something that I needed to learn about. So thank you so much for all of this!

On 2019-10-17 - by (mod) - sealing cracks doesn't stop frost damage

Sealing a surface crack against water entry does indeed reduce the chances of frost damage in Illinois or other freezing climates.

Take a look at CONCRETE SHRINKAGE CRACKS for help convincing yourself that this is just that and not slab settlement.

On 2019-10-08 by Terry

I have a covered patio w/ a 14.5 x 10.5 ft concrete slab that is around 4 inches thick. There are two posts supporting the roof over the patio, on the SE and SW corners of the slab. This past spring I noticed a thin crack extending from the patio door to the slab edge by the lawn.

The crack is in the approx center of the slab (91" from east side of slab, 83" from west side). The crack is now a little wider than when I first noticed it, but is probably less than 1/64 of an inch.

As best I can tell, the crack extends two inches into the slab. I'm considering applying a concrete sealant to keep water out of the crack as winter approaches (I live in southern Illinois), in hopes of slowing the spread of the crack. Is this advisable? Thanks.

On 2019-08-28 by (mod) - cracks in a below-sea-level car park

Re-posting from private email:

Hi our car park which is below sea level the cracks leak at high tide if we put pressure relief valve in and let it run all the time will it stop the leaking thanks rob

Moderator reply:

Robert

I'm unclear how a pressure relief valve would have anything to do with the seawater entry into a below-sea-level car park but perhaps we are not thinking of the same component.

A combination of sub-slab waterproofing (perhaps pumping bentonite clay), sealing cracks (foundations are not normally built to be absolutely waterproof), and possibly a pumping system (sump pump to draw water from below the slab and discharge it to a suitable location) would work if the pump is sufficiently powerful (or multiple pumps and sump pits) to reduce the water pressure below the slab.

Photos of the building from outside showing elevations and proximity to sea and sea level, and also of the leaky car park from inside would be helpful.

On 2019-08-28 - by (mod) - will pressure valve stop concrete floor leaks?

Anon:

Pressure where and how?

The best way to stop leaks through concrete is to find and redirect the source of water under or outside the foundation walls or floor;

Other suggestions in a more complete guide are at https://inspectapedia.com/Wet_Basements/Basement_Waterproofing_Sealer.php BASEMENT WATERPROOFING

On 2019-08-28 by Anonymous

will pressure valve stop concrete floor leaks


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