Filling Cracks in a Basement Floor

Basements can be problematic for the homeowner. Cracks and holes in the basement floor and walls allow water and even sewage to seep into the home. In this way the home is subjected to health risks. To nip this in the bud, and prior to waterproofing, the homeowner needs to thoroughly understand the concept of filling cracks in the basement floor.

There are three main causes for cracks to appear in the home's basement floor. The first is simply poor craftsmanship when the house was first built.

Secondly, homes will settle over time which may show up in foundation problems and basement cracks and holes.

And finally, cracks in the floor are caused by pressure from the outside. This factor can exacerbate the first two causes.

The Size of the Crack Determines the Solution

If the crack is 1/8” wide or less, it is safe to seal it with a commercial waterproofing material. Generally these are made of a latex cement and epoxy compound. If the crack is any larger than that, the best way to proceed is to prepare your own mortar mix to seal the crack.

To make the mortar, mix two parts fine sand to one part cement. Add enough water to make a stiff mortar. Now just trowel the mortar into the crack, working your way from one end to the other.

Don't leave any air pockets as this will be a prime spot for the crack to reopen, especially if there is any damp pressure from outside the basement.

There will be times when the repair is made more difficult because of water seeping through as the repair is being made. Under these circumstances, more floor preparation must be made.

Using a hammer and chisel, chip into the crack forming a dovetail shape. The wide side of the dovetail should be towards the outside of the basement floor and the narrow side towards the inside. The idea is to create a wedge.

With the dovetail cut along the length of the crack, be sure to remove all the debris. A wet/dry vacuum is one of the best ways to accomplish this. Following this, trowel in the mortar mixture, once again working from one end to the other leaving no air pockets.

Excessive External Water Pressure Warrants a Weep Pipe

If the basement's crack repair fails again due to excessive external water pressure it will need to be redone. But to prevent the crack repair from failing again, it will be necessary to provide for permanent pressure relief.

The easiest way to do this is to incorporate a weep pipe into the crack.
The pipe should stick out approximately six inches and should be mortared in. Flexible tubing is connected to the pipe to route the incoming water to a drain. If no drain is available in the basement, a pump may need to be incorporated into the system to raise the water to an available drain elsewhere.

Commercial Alternatives to Repairing Basement Cracks

Sometimes the homeowner would rather have a commercial company come in and make a troublesome repair. There are companies that specialize in just this kind of work. One popular method is to use a low pressure injection system. The compound injected to seal the crack is usually a proprietary mixture of epoxies, foams, and polyurethanes.

When cracks first appear, the best course of action is to tackle the issue as soon as possible to ensure that the situation has a minimal time to worsen.