There are no perfect houses and that would include its foundation. Whether you have a new home or one that’s a hundred years old, house foundations crack. Houses shift and settle after construction. Houses will have cracks in either the cosmetic finishes or structural components. Most of these cracks have no structural significance. The common types of cracks in foundation walls will include;
Vertical (or near vertical) cracks; Just because a wall has cracked doesn’t mean that it has failed or that corrective action is required. If the crack is narrow (1/8 inch or less), is nearly vertical, has no lateral separation between the adjacent portions of the wall, and no water is leaking through the crack, no action generally is required. This is a shrinkage crack and occurs as moisture in the wall evaporates causing the wall to shrink into the voids created by the escaping water. This type of crack is controlled, or minimized but not eliminated by, using horizontal reinforcement steel, which helps distribute the stresses in the wall. If horizontal steel is present, you are more likely to get several very small cracks instead of one or two much wider cracks. Another method of limiting shrinkage cracks is to control the amount of water used in the concrete mix.
Reentrant Cracks; Whenever a concrete element has a sharp angle, there is a concentration of stress. This almost always results in a crack called a reentrant crack that emanates from the inside corner. It may be vertical, horizontal, or diagonal as it exits the corner. This phenomenon exists in nearly all materials. Round openings can dissipate the stress but this is not practical in concrete wall construction. The typical remedy to reduce this type of crack is the placement of steel reinforcement in the corners. It will not eliminate these crack but keep they tight and controlled.
Horizontal cracks; Horizontal cracks require greater scrutiny. Most residential foundation walls are designed to span from the footing or floor slab to the connection of the floor structure above. An 8-inch concrete wall in normal soil conditions usually is strong enough to withstand the forces exerted on the wall with no vertical reinforcement. Exceptions include areas with high ground water conditions or in expansive soil conditions. If there is vertical reinforcement in the wall, a horizontal crack is probably not a concern. An expert should be consulted when a horizontal crack appears to evaluate whether there is a structural risk.
These cracks typically result from one or more of the following;
1. Soil settlement beneath the footing resulting in downward movement of the footing, and shifting is common to most newly constructed homes.
2. Alteration of the local water table whenever a new home is built. Specifically, the soil beneath the home dries; the resultant soil shrinkage causes minor settlement of the footing which can result in hairline cracking in the foundation walls.
3. A new home, without of furniture and effects, does not impose a significant load on the … Read More