Get House Smart.com

A home’s foundation is, in my opinion, the most important structural system of the building. It anchors our homes to the earth and provides support to the walls and roof. It is also one of the most neglected areas I find while performing an inspection.

Foundations are constructed from several different types of materials and are designed according to soil characteristics and weight loads.

The first foundations were made of stone that was simply stacked on top of the ground high enough to keep the wooden structural components from sitting on the ground and rotting. This type of foundation is twelve to twenty-four inches thick but offers little resistance to water infiltration and pests because it has no mortar between the stones. Keeping the stones in place is an ongoing challenge as well.

Once cement became available foundation stones could be held in place for a longer period of time but the mortar between the stones eventually deteriorates and the stones will then move. This means constant maintenance is required. The amount of water infiltrating the walls is less but still occurs frequently with this type of foundation.

Brick foundations seemed to be a great improvement over stone because the bricks weighed less and were uniform in shape and size. They are laid up on top of concrete footings and provide more surface to surface contact so the walls do not have to be as thick as the stone ones. Bricks can also be stacked and mortared in a number of different ways to look attractive. However, because bricks are porous they deteriorate when they are in contact with damp soil for long periods of time.

Foundations constructed of manufactured concrete blocks became standard practice for several decades. The blocks are hollow, typically eight inches tall and eight inches wide making wall construction relatively short work. They are also laid up on top of footings and mortared in place. Metal rods or wire is inserted between the blocks during construction to provide reinforcement. A dampproof coating is applied to the exterior surface prior to backfilling to prevent moisture infiltration. The blocks extend two to four courses above original grade. Vertical cracks along mortar joints due to settling are common but may allow water infiltration to occur. Horizontal cracks and stepped cracks are signs of wall displacement and require immediate expert attention.

Poured wall foundations have become very popular over the years and is the foundation of choice in many parts of the country today. This foundation is made of concrete that is poured between pairs of steel forms that are temporarily held together with metal ties and pins. Re-bar is inserted uniformly throughout the concrete to provide reinforcement. Once the concrete has cured the forms are removed and a dampproof coating is applied to the exterior surface. Diagonal cracks near window openings and vertical cracks at construction joints are common but may allow water infiltration to occur. Any signs of wall displacement should be immediately investigated by a foundation expert.

Preserved wood foundations (PWF) are constructed entirely of pressure-treated wood. Top and bottom wall plates, wall studs, and blocking are assembled. The exterior side of the wall frame is then covered with a double layer of plywood. All plywood seams are caulked and covered with polyethylene for dampproofing purposes. The wall assembly rests on a bed of gravel. The spaces between the wall studs can be insulated and interior finishing is much easier to complete than with block or concrete walls. Wall displacement is rare but is typically the only defect associated with this type of foundation.

Backfill – To replace soil that was initially removed to allow for construction of a foundation.

Cure – The drying and hardening process associated with concrete.

Course - Horizontal row of bricks, blocks, etc..

Displacement - Deviation or movement from a set line, such as bowing, caused by lateral forces.

Drystone Foundation – Foundation constructed of stone without mortar.

Footing – Widened concrete pad located below ground used to provide support and stability to foundation components.

Mortar – A mixture of cement, aggregates, and water used to hold masonry in place.

Mortared Stone Foundation – Foundation constructed of stone and mortar.

Re-bar – Small diameter metal bars placed inside concrete to provide additional strength.

Structure – Components that provide support, i.e. foundation, framework.