Why Cracks in Basement Floors Can’t be Fixed by Urethane Injection


So, your brother-in-law comes by to look at your leaky basement and points out that the water appears to be seeping out of a number of cracks in your basement floor.  He says you should have the cracks injected because that’s what he had done to cracks in his basement wall and they stopped leaking.

So you call in the basement waterproofing company and, after their guy explains what makes floor cracks seep water, he shocks you by telling you that, despite your all-knowing brother-in-law’s advice, injection won’t fix the seeping basement floor cracks.

Why Urethane Injection is the Wrong Repair for Cracks in Basement Floors

Basement waterproofing companies inject wall cracks in poured concrete foundations all the time.  It’s an extremely effective remedy and can be done quickly at a reasonable cost.  It’s a great, permanent repair for non-structural wall cracks.  For floor cracks?  Not so much.  Here’s why.

The compacted soil outside a home's foundation exerts a great deal of pressure against the foundation walls; it's this pressure that often causes the crack.  When this soil gets saturated, it causes water to seep in through wall cracks.

When a basement waterproofing technician injects a wall crack, he will typically inject an expanding urethane product.  The urethane will enter the crack and expand until it fills it all the way through to the outside soil.  The urethane sealant actually makes use of the surrounding soil as a firm barrier to help it create a solid repair.

By contrast, a typical basement floor usually consists of a comparatively thin (4” or so) layer of concrete.  This concrete is usually poured over a bed of gravel and, in newer construction, a plastic vapor barrier.  The soil under the basement floor does not move and exert pressure like soil against foundation walls but water below the floor is under what is called hydrostatic pressure.  If a basement waterproofing contractor were to inject a crack in a basement floor, the urethane would indeed prevent further seepage but would do nothing to relieve the hydrostatic pressure.

As a result, the water that had been seeping upward through the floor cracks would remain under pressure and just find another way into your basement, most likely through the cove joint.

The same would apply for epoxy injection, for those basement waterproofing companies that still use this older material.

So, if injection doesn’t work on floor cracks, what does?  The answer, as it is for many basement waterproofing questions, is interior drain tile.

The only way to solve the seepage problem is to relieve the hydrostatic pressure and the only way to do so is to install interior drain tile.  With drain tile in place on the inside of foundation footings, the ground water under pressure has somewhere to go – the pressure causes it to seep through the gravel bed surrounding the drain tile and into the pipe that carries it to a sump pump.

Don’t waste your time and money trying to patch up floor cracks.  The pros at U.S. Waterproofing have been diagnosing and solving basement seepage problems for more than 55 years and they’ve installed literally miles of interior drain tile.  Send your brother-in-law home and schedule a free consultation.

Have a question about how floor cracks happen or why they leak?  Ask it in the Comments box below.



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