Filling and Sealing Cracks in Concrete

Cracks and small holes can appear in concrete for a number of reasons, including foundation settling. The first step when filling or sealing cracks in concrete is to determine the size and severity of the holes and cracks. Cracks and holes in the concrete which are not vital to structural integrity, as well as minor cracks in the foundation can be dealt with by a homeowner. Larger, expanding cracks should be dealt with by a professional.

Before patching any cracks in concrete, the surface should be thoroughly prepared. All loose material should be removed from the crack, using a wire brush and masonry chisel. Then all remaining debris or dust should be vacuumed out with a hand vacuum.

The procedure to patch the cracks in concrete varies depending upon the size and depth of the crack or hole. When small cracks in concrete are present that do not threaten the stability of the house, the fastest way to seal them is to fill them with gray latex masonry caulk. If the crack or hole is deep, a piece of fiberglass insulation can be inserted into the hole, and the caulk added on top of it. The masonry caulk should be inserted with a caulking gun and smoothed with a trowel or putty knife.

If the holes in the concrete are deep, the hole should first be cleaned with a wire brush. Using a hand vacuum, the debris and dirt can then be removed from the hole, and the edges coated with a latex bonding liquid. A concrete patch product can then be mixed with water, and bonding liquid added. This mixture is then poured into the hole and smoothed with a flexible knife or trowel.

If the cracks are in the concrete foundation, they should be assessed for stability. This can be done by monitoring the cracks over several months, especially during the spring and the fall. The cracks should be marked for width and length, and a foundation specialist called if the crack moves more than 1/16th of an inch (1.6 mm).

If the foundational cracks in concrete are stable, a cold chisel can be used to widen the crack. Create a backward-angled cut that is wider at the base than at the surface. The crack should be cleaned out with a wire brush and filled with expanding insulating foam. Next, hydraulic cement should be mixed, according the instructions of the manufacturer, and troweled into the crack, beginning at the bottom of the crack. Cement should be added in layers until the patch is a little bit higher than the surrounding area, then smoothed with a trowel.