The House Foundation

The house foundation and how to Build a foundation:

Phase 1: Foundations

Most often, materials such as concrete blocks, preserved wood, cast-in-place concrete, or steel foundations are used for foundation building. The foundation is the strong-hold of the house; it carries the floor, wall, roof and other building loads, which includes weight from the occupants and other external weights such as snow. It is wise to consult with local builders to see what practices they used, since you should use proven methods when creating the foundation. At times, unstable soils that you come across can change the construction plan for your foundation.

Preparing the formwork for the walls is a very important step. It must be well-braced, tight and tied in a way so that it can withstand the pressure of the concrete. You can either build formwork from lumber or plywood with the appropriate framing members (built in sections), or use reusable forms. Reusable forms are made of plywood or steel. We used steel form ties to hold the two sides of the framework together, and once the concrete was set, we can broke off the ties.

Steel ties and separators were also used to hold the forms together and to maintain the width needed. If you decide to use wood spacer blocks, you need to remove them from the concrete. There are also new types form products being manufactured in Canada that can ease the process of foundation building. These new advances make it easy to work with formwork and insulation for concrete walls, and can eliminate steps from the process when building your own house.

The thickness we used for our foundation wall was 6 in. (150 mm) but the thickness can vary depending on the depth of the foundation below grade. Typical thickness ranges from 6 to 12 in. (150 mm – 300 mm).  When working with the formwork for drainage, it is best to use coarse granular mat or crushed stone around the perimeter and under the basement slab. Our builder spread the layer of stone around the footings in advance so that there was a dry, clean surface to work on.

Once the concrete has set and acquired enough strength to support the loads, you can remove the forms. Typically, this takes about 2 days but one week is ideal especially when it is cold outside. When you remove the forms, all of the recesses and holes from the form ties have to be sealed with dampproofing material or cement mortar.

At times, uncontrolled cracking can occur in the concrete slabs and walls. To help prevent this, you can use steel reinforced rods or vertical control joints that are properly placed to help minimize the cracks. When using control joints, put them in places where there is natural weakness (such as planes of windows, doors, etc.).

Preserved Wood Foundations

Wood foundations are best suited for low-rise dwellings or multiple dwellings. Make sure that the wood you use has been properly treated; look for a certification mark showing the material was treated according to local certifications. The size, species and grade of studs and thickness of plywood depeneds on stud spacing and backfill height, and the number of stories that the house will have.

Typically, when using a wood foundation to build your home, the construction follows the same methods used in house framing with some added bracing requirements. The foundation uses pressure-treated wood footings with pressure-treated bottom and top plates. All of the wood used in the foundation must be pressure treated that use chemical preservatives in accordance with your national standards. Using properly treated wood ensures that the wood is highly resistant to decay organisms and insects.