Foundation slippage is a common type of foundation damage found in homes built on slopes. With this type of damage, a foundation element (wall, footing, slab, or column) can begin to move downhill in response to gravitational forces, soil pressure, and other factors. Since foundation elements are generally joined with a combination of steel reinforcement, continuous masonry, or truss; multiple elements can be affected when one element changes.
If left unaddressed, foundation warping is likely to worsen over time. Homeowners occupying slopes are advised to contact a foundation repair specialist if they notice damage to the foundation. When the proper repairs are made in a timely manner, high repair costs and the most dangerous damage to the foundation can be avoided.
Sloping sites present problems
Contractors prefer to build a house on a flat, open site, but they don’t always get away with it. Sloped sites often develop because flat sites are no longer available. They can also be chosen due to attractive views and other features such as rocky outcrops to create a special appeal. Regardless of the reason for developing a sloping site, homeowners have reason to be concerned when soil creep causes foundation damage.
Generally, when landslide occurs, a number of forces and factors are involved. Most obviously, the gravitational force causes the ground pressure to increase as the slope becomes steeper. Vegetation generally helps stabilize a steep slope, because plant roots consolidate the soil and also help absorb excess moisture. However, vegetation also adds weight to the soil. You can increase downward pressure on a foundation if most of the roots are above the glide plane where soil movement is most likely to occur.
A discussion of soil movement generally involves water. Soil stability is enhanced by a certain moisture content, in the same way that wet sand can be molded to create a solid shape. However, adding more water to a sand sculpture will cause it to crumble and wash out. The soil can behave in a similar way. On an inclined site, the force of gravity begins to affect the soil when a certain level of moisture saturation is reached.
Base creep can also be caused by clay-rich soil that naturally expands as it absorbs moisture. This type of soil pressure often damages foundations on flat sites. On a sloped site, the expansion of the soil generally causes a downhill push against the foundation.
Tiebacks and Tiebeams solve foundation problems
A foundation repair contractor is the best professional to diagnose and repair foundation slippage on a sloped site. Helical ties and tie rods are possible solutions to stop slippage and restore foundation stability.
A helical tie is a steel anchor equipped with helical plates that allow technicians to drive the anchor into the ground like a giant screw. Typically, a series of these anchors go through the foundation wall on the uphill side of the house and sink deep into the ground. Such an installation effectively fixes the upper foundation wall on the slope. The same repair technique is used to stabilize and restore retaining walls that lean due to soil pressure.
Since it is usually the foundation wall on the downhill side of the house that slides down, the repair strategy often involves installing joists to connect the stable uphill wall to the downhill wall. The combination of tie downs and tie beams is a commonly used repair strategy. However, your foundation specialist will likely suggest other repair work to help control drainage so that the soil around the house does not become too heavy or saturated.