General Description: Foundation walls are sometimes underdesigned for the lateral earth pressure of the backfill soils. Also, as a house ages, the foundation drainage system may degrade or become compromised and excess water pressure can build up against the foundation wall. If the wall is not strong enough to resist the lateral loads, it can buckle, bow, or lean inward. Each of these mechanisms requires it's own repair method.
Bowing or Buckled Walls
Description: This type of movement is associated with insufficient bending strength in the foundation wall. The most common evidence of this type of movement is a long horizontal crack in a mortar joint of masonry block. You can also place a 4-foot level against the wall and notice that the level will "rock" or pivot over the crack. Common causes of this type of wall movement consist of lack of vertical reinforcing in the wall or excess hydrostatic pressure developing behind the wall.
Recommended repair procedure: Carbon Fiber/Kevlar straps are typically the most economical and feasible stabilization method. It is also a clean and quick method that is less noticeable after the repair is complete. The straps are as thin as a dime and are hard to notice if painted over. Most installations can be accomplished in one day or less and cause little disturbance to the basement. Another, more traditional repair method consists of installing vertical I-beams against the bowing wall. The I-beam is anchored at the bottom to the concrete floor and at the top to first floor structure. The gap between the I-beam and the wall is shimmed to transfer wall loads to the I-beam. This method is much more obstrusive to the basement than the carbon fiber straps.
Bowed wall after Carbon Fiber/Kevlarä straps are installed.
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Description: This type of movement is associated with insufficient bracing at the top of the wall. Most foundation walls have sufficient bracing at the top of the wall by the first floor structure of the home, especially when the floor joists are perpendicular to the wall. Insufficient bracing can be caused by improper connections of the wall to the sill plate and floor structure above or by parallel floor joists where additional cross bracing is not added. Excess hydrostatic pressure building up behind the wall can compound the problem by adding to the forces tending to lean the wall inward. If a wall is not sufficiently braced at the top, it will lean inward and not bow.
Recommended repair procedure: There are a number of different ways to brace foundation walls and prevent further leaning. It could be as simple as improving the connections of the wall to the floor structure above or adding cross bracing between bays of parallel floor joists. For severe cases, or where top bracing cannot be provided, it may be necessary to install helical screw tiebacks or a Dura-GripÔ wall repair system.
Description: Drying shrinkage cracks are a common occurence in cast-in-place concrete walls. Drying shrinkage is attributed to the loss of water from cement gel as hardened concrete continues to cure, resulting in a decrease in volume in the concrete. They do not pose a threat to the structural integrity of the foundation, but can allow water to infiltrate the basement.
Recommended repair procedure: We can stop the infiltration of water through shrinkage cracks by injecting polyurethane foam into the crack. The polyurethane foam will push water out of the crack and keep it out after curing. The product will last a lifetime since it is very stable and will only breakdown in the presence of fire or direct sunlight.