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STRUCTURAL INSPECTIONS & DEFECTS

ADVANCED INSPECTION METHODS
AGE of a BUILDING - how to determine
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BASEMENT WATERPROOFING
BEST CONSTRUCTION PRACTICES GUIDE
BRICK FOUNDATIONS & WALLS
BRICK STRUCTURAL WALL Loose Bulged
BRICK WALL THERMAL EXPANSION CRACKS
BRICK VENEER WALL Loose, Bulged
BRICK WALL DRAINAGE WEEP HOLES
BUCKLED FOUNDATIONS due to INSULATION?
BUILDING DAMAGE ASSESSMENT & REPAIR
BUILDING SAFETY HAZARDS GUIDE
BUILDING SETTLEMENT

CHIMNEY INSPECTION DIAGNOSIS REPAIR
COLD POUR JOINTS, CONCRETE
COLUMNS & POSTS, DEFECTS
CONCRETE FOUNDATIONS
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Cracks, Checking or Splitting Beams & Log Homes

DECK & PORCH CONSTRUCTION
DECK COLLAPSE Case Study
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EARTHQUAKE DAMAGED FOUNDATIONS

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FOUNDATION WATERPROOFING
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More Information

Photograph of a concrete slab control joint How to Seal Cracks in Concrete Floors & Walls
     

  • SEAL CRACKS in CONCRETE, How To - Recommended methods for sealing cracks in concrete floors & slabs - How to seal control joint & expansion joint cracks in concrete slabs
    • 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?
  • BASEMENT LEAKS, INSPECT FOR - separate article
  • SLAB CRACK EVALUATION - home
  • SLAB CRACK REPAIR - home
    • CRACK REPAIR STANDARDS for FLOORS - separate article
    • CONTROL JOINT CRACKS in CONCRETE - separate article
    • POLYURETHANE FOAM INJECTION - separate article
    • SEAL CRACKS in CONCRETE, How To
    • SHRINKAGE CRACK REPAIR - separate article
    • SLAB CRACK EVALUATION - separate article
    • VERTICAL FOUNDATION MOVEMENT REPAIR - separate article
  • FOUNDATION REPAIR METHODS - separate article
  • Questions & answers about sealing floor or foundation or wall cracks, water entry through cracks, crack sealing approaches, costs, reliability
  • References

Click to Show or Hide Related Topics

  • FOUNDATION DAMAGE & REPAIR GUIDE - home
  • BUILDING SETTLEMENT
  • DEFECTS LIST - STRUCTURE, FOUNDATION
  • DISASTER BUILDING INSPECTION & REPAIR
  • EARTHQUAKE DAMAGED FOUNDATIONS
  • FLOOD DAMAGED FOUNDATIONS
  • FOUNDATION CONSTRUCTION TYPES
  • FOUNDATION CONTRACTORS, ENGINEERS
  • FOUNDATION CRACK EVALUATION
  • FOUNDATION DAMAGE REPORTS
  • FOUNDATION DAMAGE SEVERITY
  • FOUNDATION DRAINS / FRENCH DRAINS
  • FOUNDATION FAILURES by MOVEMENT TYPE
  • FOUNDATION FAILURES by TYPE & MATERIAL
  • FOUNDATION INSPECTION METHODS
  • FOUNDATION INSPECTION STANDARDS
  • FOUNDATION INSULATION OPTIONS
  • FOUNDATION MATERIALS, Age, Types
  • FOUNDATION MISSING INCOMPLETE
  • FOUNDATION MOVEMENT ACTIVE vs. STATIC
  • FOUNDATION REPAIR METHODS
  • FOUNDATION WATERPROOFING
  • FRAMING DAMAGE, INSPECTION, REPAIR - home
  • FROST HEAVES, FOUNDATION, SLAB
  • SINKHOLES, WARNING SIGNS
  • SINKING BUILDINGS
  • SITE FACTORS AFFECTING FOUNDATIONS
  • SLAB CRACK EVALUATION
  • SLAB CRACK REPAIR
  • WATER ENTRY in BUILDINGS
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

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.

Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.

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

Here 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.

Photograph of a sketch of typical crack patterns in a poured concrete slab

Also see How to Repair Foundation Cracks Using Polyurethane Foam Injection which explains how to use this special method for sealing non-structural cracks in masonry walls or floors, and see FOUNDATION REPAIR METHODS for a more extensive discussion of types of foundation damage and how it is repaired.

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.

Warning: some crack sealing operations may make crack diagnosis or monitoring more difficult

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.

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:

  • Using a flexible sealant in a structural crack may make it difficult to see small amounts of future movement since the sealant may stretch and tolerate small increases in crack width. This can increase the difficulty of crack monitoring and diagnosis
  • Using a sealant in a foundation or floor slab crack may fail to address the underlying cause of the problem such as foundation settlement or frost heaving which need to be addressed
  • Using a sealant in a crack, except for some structural epoxies, may seal but not "repair" the damage in any structural sense

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.

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

  • Pre-fabricated control joint strips of plastic or other material
  • Masonry caulks or flexible (typically polyurethane based) radon sealant caulks (product sources are listed at Seal Cracks by Polyurethane Foam Injection)
  • Semi rigid epoxy resin crack fillers (discussed in this article). Epoxy products intended for concrete expansion joints. These products are described and their sources listed below in our discussion of this method that includes injection ports and (usually) two-part epoxy resins injected into the crack.
  • Special poly urea caulks designed as a joint filler - polyurethane foam injection to seal cracks. This method is discussed below. Separately we discuss this method in detail along with product sources at Seal Cracks by Polyurethane Foam Injection
  • Hydraulic cements for concrete or other masonry floor, foundation, or wall repairs of cracks & leaks

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.

Typical concrete crack preparation for sealant with an epoxy product

Carson Dunlop Associates' sketch below shows three common methods used to seal cracks in masonry walls in an effort to stop foundation leaks.

Concrete crack patching methods (C) Cason Dunlop Assoc

  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. 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.

    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. 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 Assoc

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

  • See our separate article Polyurethane Foam Injection for details of the procedure for using polyurethane foam to seal foundation cracks and for a list of sources & brands of polyurea or polyurethane foam sealants, caulks, and crack repair kits. .

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 un-damaged and sealed where a rigid material may fail.

List & Sources of Epoxy Grout Products

  • Elasta Gel 6170 Epoxy® flexible epoxy and expansion joint sealant, two component, no VOC, flexible epoxy resin which is rated for use on parking decks and, according to the manufacturer, Lone Star Epoxies, can also be used to repair concrete spalling on such surfaces.
  • Emecole Structural Repair Epoxy products, 50 E. Montrose Dr., Romeoville IL 60446, USA Tel: 800-844-2713, Website: www.emecole.com
    • Emecole 121 Premium - Fast Curing Crack Repair Epoxy
    • Emecole 101 Original Formula - Crack Repair Epoxy
    • Emecole 40 - Concrete Deck Repair Epoxy
    • Emecole cargon fiber reinforcement products: used by professional repair contractors where a building wall suffers large cracks or bowing. (Also see Bulged foundation Repairs.)

Quoting: Emecole Epoxies are recommended for structural cracks.  Unlike polyurethane foams, epoxies will not expand.  However, they cure to an incredibly hard solid, making them ideal for structural repairs.  Our two-component epoxies are strong, durable and reliable. After curing, Emecole Epoxies create a more powerful bond than concrete, resulting in an extremely strong repair.

  • Epoxy grouts (ANSI 118.3 1988) for tile applications (watch out for proper tile surface cleaning within the cure time; cleanup is done using water)
  • Laticrete™ epoxy grouts
  • Mar-Flex Epoxy Injection Concrete Crack Repair Kit, Tel: 800-498-1411, Website: www.mar-flex.com

    Quoting: Low-pressure injection and repair of approximately 8-10 lineal feet. Contains the following; (1 jar 8oz.) Mar-flex Crack Seal (1 jar 8oz.) Port Adhesive (2) Wooden Sticks (12) Surface Ports and Caps (2 Cartridges) Mar-flex Injection Polyurethane/Epoxy Resin 1:1 (2) 3/8" :24 Mixing Nozzles (1) Injection Hose Assembly with plastic shut-off valve (2 pair) Latex Gloves (1) Plastic Trowel (1) Wire Brush (1) Drop Cloth (1) Complete Instructional DVD. The company also offers low-viscosity crack filler that can be injected into both dry and damp cracks and a "Seal & Peel" crack repair kit.
  • Polygem Epoxy pastes, resins, & grouts, POLYGEM, Inc. P.O. Box 609 West Chicago, IL 60186, Tel: 888-446-3987, Website: www.polygem.com
    • Polyject #1001 LV for hairline to 1/16” cracks
    • Polyject #1001MV for 1/16” to 1/8” cracks
    • Polyject #1001 HV for 1/8” to 1/4#148; cracks
    • Polyject #1001 EHV for over 1/4#148; cracks

    Quoting: Polygem, Inc. manufactures epoxies, vinyl-esters and silicones for various industries and markets such as: Construction, Waterproofing, Mining, Industrial, Electrical, Zoological, Golf and DIY. Polygem, Inc. has been custom formulating epoxies in excess of twenty-five years and has created over 1,500 unique formulations.

  • Ramset™ Epoxy Grout - a pourable epoxy resin, also can be mixed with sand and applied with trowel.
  • Shor D 65-80®
  • Other semi-rigid, epoxy products - contact us to add products & information - no fees involved

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.

  • RadonSeal Crack Seal & Port Adhesive, Novion, Inc., 18 L'Hermitage Dr., Shelton CT 06484, Tel: 800-472-0603, Website: www.radonseal.com
  • Mar-Flex Epoxy Injection Concrete Crack Repair Kit, Tel: 800-498-1411, Website: www.mar-flex.com
    The company offers low-viscosity creack filler that can be injected into both dry and damp cracks and a "Seal & Peel" crack repair kit.

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

  • Structural repairs are needed. Epoxy, properly mixed and installed, is stronger than the concrete to which it is bonding. But as we warn above, unless you correct the cause of ongoing (such as settlement or earth loading) or cyclical (such as water or frost) structural movement & cracking, new cracks will develop in the structure
  • Very fine cracks need to be sealed - so fine that it may be difficult to inject a polyurethane foam, but still possible to inject a low-viscosity epoxy sealant. For wider cracks use a higher viscosity epoxy preparation or consider a polyurethane injection approach.
  • May provide a smoother surface for finished surfaces such as a finished basement (but seal & peel systems can also accommodate this need)

Reasons to use a polyurethane foam injection crack sealant

  • Structural repairs are not needed but sealing a crack against air or water leaks is required
  • If you expect small amounts of recurrent or cyclical building movement that might re-crack or leak where a rigid crack sealant is applied, using a flexible polyurethane sealant may prove more durable
  • If the crack is large an expanding polyurethane foam sealant may be easier to install and is also likely to be less expensive per linear foot of crack.
  • If the crack extends through the foundation wall and is large, an epoxy sealant may simply leak out of the other side of the wall or floor slab - the foam injection approach may also cause foam to extrude through the structure but is more likely to also successfully fill the crack.
  • If the crack is actively leaking an epoxy injection sealant is more likely to fail to bond properly to the masonry surfaces and a polyurethane sealant will perform more reliably. (Polyurethane sealants are moisture activated.)
  • Do-it-yourself repairs: homeowners may find this approach easier than the epoxy approach

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

  • Hydraulic cement
  • Portland cement grout (ANSI 108.10 1985)
  • Latex-modified portland cement grouts (we've used these with good success indoors in tile floors for better water resistance)
  • Epoxy grouts (described above) usually with a water-dissolved mix
  • Modified Epoxy grouts (ANSI 118.8 1988.) combining portland cement and epoxy (some sources say the chemical resistance is similar to straight Portland cement but the result is a harder grout - just what chemicals are resisted may vary among products)
  • Furan resin grouts use furfuryl alcohol in their products - no water is used. These are highly acid-resistant, also difficult to install.

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 (C) Daniel FriedmanA 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. Nevertheless 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.

Concrete slab crack (C) Daniel FriedmanFor larger floor slab cracks (such as shown in our photo at left) 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.

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 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.


Frequently Asked Questions (FAQs)

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

  • Carson, Dunlop &
Associates Ltd., TorontoCarson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' home inspection education products include
    • The ASHI-adopted Home Inspection Training Program, and Commercial Building Inspection Courses
    • The Home Inspection Home Study Course, and publications such as
    • The Home Reference Book, a reference & inspection report product for building owners & inspectors.
      Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a ten percent discount on any number of copies of the Home Reference Book purchased as a single order. Just enter HRBUS10 in the order payment page "Promo/Redemption" space. Note: InspectAPedia.com ® editor Daniel Friedman is a contributing author.
    • The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones
    • Home Inspection Report writing materials, including the Horizon Software System that manages business operations, scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
    • The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors
  • How to Seal Cracks in Concrete - you are currently on this web page.
  • Shrinkage Crack Repairs
  • Polyurethane Foam Injection for details of the procedure for using polyurethane foam to seal foundation cracks.
  • Cracks at Control Joints in Concrete how we prevent shrinkage cracks in poured concrete floors and walls
  • FOUNDATION REPAIR METHODS for our catalog of Foundation Repair Methods - Examples of Typical Foundation Repairs for various types of foundation cracks, leaks, settlement, movement, or other failures
  • "Best Practices for Concrete Sidewalk Construction," Balvant rajani, Canadian National Research Council
  • "Design Considerations for Perlite Roof Slabs," a chapter in "Perlite Concrete Grade for Lightweight Concrete Construction", United Perlite Corporation
  • Quality Standards for the Professional Remodeling Industry, National Association of Home Builders Remodelers Council, NAHB Research Foundation, 1987.
  • Quality Standards for the Professional Remodeler, N.U. Ahmed, # Home Builder Pr (February 1991), ISBN-10: 0867183594, ISBN-13: 978-0867183597
  • Lone Star Epoxies, Rowlett TX, product literature, includes application instructions for this flexible epoxy resin concrete expansion joint sealer. ls@lsepoxies.com - 10/06/08
  • Ramset™ Epoxy Grout, Australia,
  • Laticrete™ Epoxy grouts
  • Building Failures, Diagnosis & Avoidance, 2d Ed., W.H. Ransom, E.& F. Spon, New York, 1987 ISBN 0-419-14270-3
  • Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 ISBN-13: 978-0471331728
  • Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039
  • Masonry Design for Engineers and Architects, M. Hatzinikolas, Y. Korany, Canadian Masonry (2005), ISBN-10: 0978006100, ISBN-13: 978-0978006105
  • Masonry Structures: Behavior and Design, Robert G. Drysdale, Ahmid A. Hamid, Lawrie R. Baker, The Masonry Society; 2nd edition (1999), ISBN-10: 1929081014, ISBN-13: 978-1929081011
  • Quality Standards for the Professional Remodeler, N.U. Ahmed, # Home Builder Pr (February 1991), ISBN-10: 0867183594, ISBN-13: 978-0867183597
  • Slab on Grade Foundation Moisture and Air Leakage, U.S. Department of Energy

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

  • Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
  • Home Reference Book - Carson DunlopThe Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

    Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
  • Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
  • Avongard foundation crack progress chart for structural crack monitoring
  • Basement Moisture Control, U.S. Department of Energy
  • Crawl Space Moisture Control, U.S. Department of Energy
  • Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.
  • Domestic Building Surveys, Andrew R. Williams, Kindle book, Amazon.com
  • Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting:
    A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.
  • Guide to Domestic Building Surveys, Jack Bower, Butterworth Architecture, London, 1988, ISBN 0-408-50000 X
  • "Avoiding Foundation Failures," Robert Marshall, Journal of Light Construction, July, 1996 (Highly recommend this article-DF)
  • "A Foundation for Unstable Soils," Harris Hyman, P.E., Journal of Light Construction, May 1995
  • "Backfilling Basics," Buck Bartley, Journal of Light Construction, October 1994
  • "Inspecting Block Foundations," Donald V. Cohen, P.E., ASHI Reporter, December 1998. This article in turn cites the Fine Homebuilding article noted below.
  • "When Block Foundations go Bad," Fine Homebuilding, June/July 1998
  • Masonry structures: The Masonry House, Home Inspection of a Masonry Building & Systems, Stephen Showalter (director, actor), DVD,
  • Masonry, Engineered: Using the Canadian Code, J. I. Gainville, Cantext publications (1983), ASIN: B0007C37PG
  • Masonry, Non-reinforced masonry design tables, Hans J. Schultz, National Concrete Producers Association and the Canadian Masonry Contractors Association (1976), ASIN: B0007C2LQM
  • Moisture Control in Buildings, U.S. Department of Energy
  • Moisture Control in Walls, U.S. Department of Energy
  • Quality Standards for the Professional Remodeling Industry, National Association of Home Builders Remodelers Council, NAHB Research Foundation, 1987.
  • "A Hole in the Ground Erupts, to Estonia's Delight", New York Times, 9 December 2008 p. 10.
  • History of water usage in Estonia: (5.7 MB PDF) jaagupi.parnu.ee/freshwater/doc/the_history_of_water_usage_systems_in_estonia.pdf
  • "Quebec Family Dies as Home Vanishes Into Crater, in Reminder of Hidden Menace", Ian Austen, New York Times, 13 May 2010 p. A8. See http://www.nytimes.com/
  • "Quick Clay", Wikipedia search 5/13/2010 - http://en.wikipedia.org/wiki/Quick_clay
  • Florida DEP - Department of Environmental Protection, & Florida Geological survey (http://www.dep.state.fl.us/geology/default.htm) on Florida sinkholes: Effects of Sinkholes on Water Conditions Hernando County, Florida, Brett Buff, GIS in Water Resources, 2008, Dr. David R. Maidment, Photos - Tom Scott, Florida Geographic Survey - Web Search 06/09/2010 - http://www.dep.state.fl.us/geology/geologictopics/jacksonsink.htm
    and - http://www.dep.state.fl.us/geology/geologictopics/sinkhole.htm
    also see
    Lane, Ed, 1986, Karst in Florida: Florida Geological Survey Special Publication 29, 100 p.
  • Foundation Engineering Problems and Hazards in Karst Terranes, James P. Reger, Maryland Geological Survey, web search 06/05/2010, original source: http://www.mgs.md.gov/esic/fs/fs11.html
    Maryland Geological Survey, 2300 St. Paul Street, Baltimore, MD 21218
  • "Frost Heaving Forces in Leda Clay", Penner, E., Division of Building Research, National Research Council of Canada, Canadian Geotechnical Journal, NRC Research Press, 1970-2, Vol 7, No 1, PP 8-16, National Research Council of Canada, Accession number 1970-023601, Quoting from original source

The frost heaving forces developed under a 1 ft. (30.5 cm) diameter steel plate were measured in the field throughout one winter. The steel plate was fixed at the ground surface with a rock-anchored reaction frame. heave gauges and thermocouples were installed at various depths to determine the position and temperature of the active heaving zone. The general trend was for the surface force to increase as the winter progressed. when the frost line approached the maximum depth the force was in excess of 30,000 lb (13,608 KG). Estimates of the heaving pressure at the frost line ranged from 7 to 12 psi (0.49 to 0.84 KG/cm) square during this period. The variation of surface heaving force was closely associated with weather conditions. Warming trends resulting in a temperature increase of the frozen layer caused the forces to decline.

  • [1] Sarah Cervone, [web page] data from the APIRS database, Graphics by Ann Murray, Sara Reinhart and Vic Ramey, Vic Ramey is the editor. DEP review by Jeff Schardt and Judy Ludlow. The web page is a collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection contact: varamey@nersp.nerdc.ufl.edu [A primary resource for this article
  • [2] Center for Cave and Karst Studies or the Kentucky Climate Center, both at Western Kentucky University
  • Vanity Fair - web search 06/04/2010 http://www.vanityfair.com/online/daily/2010/06/what-caused-the-guatemala-sinkhole-and-why-is-it-so-round.html
  • Virginia Department of Mines, Minerals and Energy, www.dmme.virginia.gov Virginia Department of Mines, Minerals and Energy Division of Mineral Resources 900 Natural Resources Drive, Suite 500 Charlottesville, VA 22903 Sales Office: (434) 951-6341 FAX : (434) 951-6365 Geologic Information: (434) 951-6342 http://www.dmme.virginia.gov/ divisionmineralresources.shtml - Web search 06/09/2010
  • Newton, J. G., 1987, Development of sinkholes resulting from man's activities in the eastern United States: US Geological Survey Circular 968, 54 p.
  • Sinclair, W. C., 1982, Sinkhole development resulting from ground-water withdrawal in the Tampa Area, Florida: U.S. Geological Survey Water-Resources Investigations 81-50, 19 p.
  • White, W. B., 1988, Geomorphology and Hydrology of Karst Terrains: Oxford University Press, New York, 464 p.
  • Williams, J. H. and Vineyard, J. D., 1976, Geologic indicators of subsidence and collapse in karst terrain in Missouri: Presentation at the 55th Annual Meeting, Transportation Research Board, Washington, D.C.
  • Barry F. Beck, A. J. (1999). Hydrogeology and Engineering Geology of Sinkholes and Karst. Rotterdam, Netherlands: A. A. Balkema.
  • Beck, B. F. (2003). Sinkholes and the Engineering and Environmental Impacts of Karst. Huntsville, Alabama: The American Society of Civil Engineers.
  • Beck, B. F. (2005). Sinkholes and the Engineering and Envrionmental Impacts of Karst. San Antonio, Texas: The American Society of Civil Engineers.
  • Tony Waltham, F. B. (2005). Sinkholes and Subsidence, Karst and Cavernous Rocks in Engineering and Construction. Chichester, United Kingdom: Praxis Publishing.
  • Whitman D., G. T. (1999). Spatial Interrelationships Between Lake Elevations, Water Tables, and Sinkhole Occurence in Central Florida: A GIS Approach. Photogrammetric Engineering and Remote Sensing , 1169-1178.
  • Cited References from this article:
  • #3. Detecting Sinkholes with Geophysics, Enviroscan, Inc., Lancaster PA 717-396-8922 email@enviroscan.com www.enviroscan.com 2003
  • Sinkholes in Guatemala, Guatemala City, Wikipedia - web search 06/04/2010 - http://en.wikipedia.org/wiki/Guatemala_City

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