Foundation creep is a common type of foundation damage found in houses built on sloping sites. With this kind of damage, a foundation element (wall, footing, slab or pier) can begin to move downhill in response to gravitational forces, soil pressure and other factors. Since foundation elements are usually tied together with a combination of steel reinforcement, continuous masonry or framing; multiple elements can be affected when one element shifts.
If not addressed, foundation creep is likely to worsen over time. Homeowners who occupy sloping sites are well-advised to contact a foundation repair specialist if they notice foundation damage. When proper repairs are done in a timely fashion, high repair costs and more perilous foundation damage can be avoided.
Sloping Sites Present Problems
Contractors prefer to build a house on a flat, open site, but they don’t always get their way. Sloping sites are often developed because flat sites are no longer available. They can also be chosen because of attractive views and other features like rock outcroppings to create special appeal. Regardless of the reason for developing a sloping site, property owners have reason to be concerned when soil creep causes foundation damage.
A number of forces and factors are usually involved when soil creep occurs. Most obviously, gravitational force causes soil pressure to increase as the slope grows steeper. Vegetation usually helps to stabilize a steep slope, because plant roots consolidate the soil and also help to absorb excess moisture. However, vegetation also adds weight to the soil. It can increase downward pressure on a foundation if most of the roots are above the slip plane where soil movement is most likely to occur.
A discussion of soil movement usually involves water. Soil stability is enhanced by certain moisture content– in the same way that damp sand can be molded to create a solid form. However, adding more water to a sand sculpture will cause it to crumble and wash away. Soil can behave in similar fashion. On a sloping site, the pull of gravity begins to effect soil when a certain level of moisture saturation is attained.
Foundation creep can also be caused by clay-rich soil that expands naturally as it absorbs moisture. This type of soil pressure often damages foundations on flat sites. On a sloping site, soil expansion typically 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 creep on a sloping site. Helical tiebacks and tiebeams are possible solutions to stop the creep and restore stability to the foundation.
A helical tieback is a steel anchor equipped with helical plates that allow technicians to drive the anchor into the soil like a giant screw. A series of these anchors are typically driven through the foundation wall on the uphill side of the house, and deep into the soil. Such an installation effectively pins the upper foundation wall into the slope. The same repair technique is used to stabilize and restore retaining walls that are tilting due to soil pressure.
Since it’s usually the foundation wall on the downhill side of the house that is creeping downward, the repair strategy often involves installing beams to connect the stable uphill wall with the downhill wall. The combination of tiebacks and tiebeams is a commonly used repair strategy. However, the foundation specialist is likely to suggest other remedial work to help control drainage so that the soil around the house doesn’t get too heavy or too saturated.