Residential foundations are typically constructed in one of two ways. Both start with a poured concrete footing to help support the foundation walls and distribute the weight of the structure.
Currently, the most common approach is to construct a system of forms on top of the footings and pour walls of concrete to form a monolithic foundation.
In some parts of the country, a masonry foundation is built on top of the footings, most often of concrete blocks, also known as “cinder” blocks or CMUs (concrete masonry units.) In the past and occasionally for specialized construction, bricks or stones might be used.
Either foundation, properly built, will do a fine job of supporting the structure and containing a basement or crawl space. Both, however, are prone to cracking when the foundation sinks or settles or when over-saturated soil outside the foundation creates lateral pressure that pushes the walls inward.
The cracks that ensue may be structural or non-structural. When structural cracks occur it is not so much a matter of repairing the crack as it is stabilizing the entire wall or raising and stabilizing the foundation and these repairs can cost thousands of dollars. Non-structural cracks seep water into the basement or crawl space and must be repaired to avoid problems with mold, rot, high humidity and destruction of furnishings and other property.
These non-structural cracks are very common in both types of foundation and are the leading source of seepage in poured concrete construction. Professional repair is needed to ensure an effective and permanent fix and many homeowners’ first question is “How much will it cost?”
Seeping cracks in a poured concrete foundation can be repaired from either the inside or outside of the basement. The inside method, preferred when possible, involves cleaning out the crack of loose concrete and other debris, inserting plastic injection ports at regular intervals along its length and sealing over the crack with a coat of epoxy. Once the epoxy has cured, the injection ports are used to fill the crack with expanding polyurethane that seals the crack all the way to the outside soil and remains flexible when cured to prevent re-cracking caused by minor foundation movement.
Once the repair has cured the epoxy can be scraped off the wall if desired.
The cost of repairing a crack through polyurethane injection is typically several hundred dollars and most basement waterproofing professionals will offer a reduced rate for multiple cracks. Multiple cracks, by the way, are pretty common because the pressure on foundation walls is such that offsetting cracks almost always occur.
When a basement is finished or the crack is somehow inaccessible from inside, it can be repaired on the exterior. The repair begins by digging a small-diameter hole at the site of the crack that extends down to the foundation footings.
The hole is then filled with a granular formula of sodium bentonite clay that will quickly absorb water from the surrounding soil and form a permanent water barrier on the “positive” side of the foundation wall. The remaining hole is then backfilled and the repair is invisible.
Because of the labor involved and the cost of materials, sealing a crack from the outside costs more than injecting it from within but is still a very reasonable means of preventing damaging basement seepage. Again, a reduced rate for multiple cracks is customary.
Regardless of whether the crack is best repaired from the interior or exterior, a homeowner with seeping cracks in a poured concrete foundation needs the assistance of an experienced basement waterproofing contractor. At U.S. Waterproofing, we got our start back in 1957 by specializing in exterior crack repair and have become one of the country’s largest full-service basement waterproofing companies with more than 300,000 satisfied customers on our books. Why not ask for our free advice when you spot a crack in your basement?
If you’d like to know more about the cost of repairing cracks in a poured concrete foundation, please post your questions in the Comments box below.
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