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Foundation wall or slab crack repair using polyurethane foam injection: this article explains how to use injected polyurethane foam to repair a concrete basement (or crawl area) wall or slab crack in order to stop basement or crawl space water entry or air leakage.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.Aaron Kuertz, Applied Technologies
A variety of site conditions can lead to cracks in a concrete or other masonry foundation wall. Speaking generally, foundations may be damaged and cracks may appear from innocent causes unlikely to affect the structure such as shrinkage cracks, initial settlement, or from potentially more serious causes such as ongoing settlement, unusual pressures or loading, or from improper construction.
Before repairing a foundation crack by sealing it against water entry, it is important to diagnose the cause of the crack and its effects on the building structure. If there is an underlying ongoing problem causing foundation movement or damage, that problem should be corrected.
Cracks in concrete walls that are larger than 1/4", cracks which are increasing in size, or cracks which are indicative of foundation movement should be evaluated by a professional. The diagnosis and evaluation of foundation cracks and structural foundation damage and repair methods are discussed at FOUNDATION REPAIR METHODS
Shrinkage cracks and in some cases other foundation cracks such as those caused by minor initial settlement might not be a structural concern but may still form an opening leading to water leaks into the building. Concrete shrinks as a natural process of it curing. This shrinkage causes the concrete to develop stresses and to relieve it, the basement wall cracks.
Concrete shrinkage cracks are a common condition in a concrete foundation [or also in concrete slabs unless control joints were used in the wall or floor design] and occur when concrete shrinks as it dries and cures.
Shrinkage cracks are easy to recognize and to distinguish from cracks that occur later in the life of a foundation because [usually] the cracks are not continuous and tend to extend in a very irregular line through the concrete (as shown in the photo) range in length from a few inches to the entire height of the concrete wall, extending from wall top to bottom.
Concrete shrinkage cracks virtually always extend through the full thickness of the foundation wall, which means they can provide a ready path for water entry into the building.
Common areas for a shrinkage concrete crack to develop are under a basement window, above a doorway in the middle of a long wall or where the foundation "steps down." Shrinkage cracks also often occur near the middle of a large poured concrete wall [or floor] if no control joints were used. [Concrete control joints are very often omitted in residential construction. Shrinkage cracks and how to recognize and diagnose them are discussed further at SHRINKAGE vs EXPANSION vs SETTLEMENT.
Once concrete cracks in a basement or crawl space wall or floor slab, it is possible for water to leak into a building through the crack. There are several ways to repair a basement crack leak. An easy, quick, and effective measure to stop basement or crawl space water entry through a foundation crack is to perform an injection of polyurethane foam into the basement crack. [Also be sure to find and fix the sources of water outside.]
Both commercial and home-owner "do it yourself" kits and equipment are available to seal foundation cracks using this foam method. [Photograph of this foundation crack repair kit, courtesy of Applied Technologies].
Polyurethane foams are injected into the basement crack in a liquid form. This allows a gentle and slow filling process of the basement crack that will completely fill the crack. After a few minutes the polyurethane will begin to react with the water in the crack to begin foaming. Water is actually the catalyst that converts the liquid polyurethane into foam. This foaming action increases the volume of the polyurethane up to 30 times its liquid form.
As the polyurethane foam expands it fills the basement crack from bottom to top and front to back. The finished foam will be a closed cell structure that will not allow water to leak into the basement crack. In fact, if there are any voids in the soil outside of the basement- such as under a rock or if the foundation is backfilled with gravel-the polyurethane foam will expand and extend out into the void.
The polyurethane foam forms a strong bond to the concrete. This bond will be able to withstand the hydrostatic pressure that may develop from high subsurface water levels. High underground or "subsurface" water levels are typically caused by heavy rains and most-often by failure to direct roof runoff or nearby surface runoff away from the building.
This concrete crack repair process using polyurethane injection is likely to be more successful and more durable than other crack patching methods. Surface patching of the crack is just that. Only the inside of the basement wall is covered by a repair. Chiseling out the crack and filling it with hydraulic cement only fills a portion of the crack.
Water can still enter the basement crack and will eventually force out the patch or hydraulic cement. [Forces that tend to cause separation of poorly-bonded concrete surface patches include the molecular action of crystallizing mineral salts left behind as moisture passes through the masonry wall.]
Basement crack injection is a quick repair process that stops water leaks. The technician does not have to drill into the concrete to do it. For this reason the basement crack repair is a clean process. The technician will attach ports to the surface of the basement crack that allow the liquid polyurethane to enter the basement wall and stop the leak.
Once the basement wall crack is completed, water will not be able to leak into the basement. Now the homeowner's possessions will be safe. As will any insulation on the basement walls, the drywall or the framing used to finish the basement.
List of Polyurethane Crack Sealants Products, Sources, Brands, Manufacturers
Also see SEAL CONCRETE CRACKS, HOW TO for a description of various products and methods used to seal or repair cracks in poured concrete walls, foundations, floors, & slabs. and see FOUNDATION REPAIR METHODS for a more extensive discussion of types of foundation damage and how it is repaired. [Photograph of this foundation crack repair process using foam injection, courtesy of Applied Technologies]
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