A conventional foundation is known as a “Pier & Beam” or “Crawl Space” foundation. This foundation begins with concrete footings. Concrete footings are poured into trenches in the ground. They provide a wide and stable base for the foundation walls. The footing is made of concrete and rebar. After the footings have dried, the foundation wall is built on top of the footings. This wall allows the wood floor structure to be elevated above the ground to avoid moisture problems. The foundation wall is typically concrete block filled with rebar and concrete for extra support. The foundation wall and the footings go around the outside perimeter of the home.
When the footings, the foundation wall, and the piers are in place, a wood floor system consisting of floor joists and headers is placed on top of the foundation wall and the piers. The joists and headers support the sub floor and the finished flooring material. The floor joists are spaced at 16” or 24” intervals (known as “on center”) and this allows the sub floor to be installed on top of the floor joist. Modern sub floors are made from plywood, OSB, or particleboard. In older construction, solid wood was used. Due to the high cost of lumber, solid wood is rarely used today.
To gain a better understanding of what the conventional foundation looks like and how it supports the weight of the home, look at the diagram below.
In most instances, footings or foundation walls will not be involved in the loss, but an understanding of their nature is necessary for a working knowledge of the make-up and purpose of the load bearing components. Before the footings and foundation walls can be started, a trench is dug around the perimeter or foundation line.
The foundation wall is typically a poured concrete wall or a concrete block wall.
In the diagram above, a large beam is running throughout the center of the home. In the diagram, it is called a “center girder”. It is also known as a “support beam”. This is required as dimensional lumbar (2”x10” etc) is available in standard lengths up to 16’. As most homes are deeper than 16’m a center bean (girder) must be added to allow the shorter length joists to overlap and span the depth of the home.
When the footings, foundation wall, floor joists, and center girder are installed, it is time to add the sill plate. The sill page is connected directly to the foundation wall by anchor bolts. It should be made from pressure treated wood. When the sill plate and the floor joists are in place, it is time to install the sub-floor. As noted earlier, modern sub-floors are typically made from CDX plywood, OSB, or particleboard. Older homes may have a solid wood sub floor. When the sub floor is in place, it is time for the finished floor (carpet, hardwood, vinyl, etc.)
If vinyl or ceramic tile is used, it is common to add an underlayment layer on top of the sub floor. A common underlayment material used today is ¼” luan plywood. The addition on this extra layer of material guarantees a smooth surface free of knotholes and imperfections that are common with plywood, OSB, and particleboard.
The majority of the conventional foundation losses you will see will be limited to the sub- floor and underlayment (when underlayment is present). These two items are damaged commonly by water losses and fire losses. With that in mind, you must be able to recognize and understand the material, which you will be inspecting while working insurance claims. We will be reviewing plywood, OSB, and particleboard construction at a later time.
