PATH - A Public Private Partnership for Advancing Housing Technology
[IMAGE: foundation image]Foundations and Site Work
You may be envisioning a gorgeous kitchen, a spacious master bath or a perfectly designed family room, but none of them will give you much pleasure if your house sits on a poorly built foundation. It's not sexy, but the foundation is the underpinning of quality homebuilding.
Homes with improperly built foundations settle unevenly, causing serious structural problems, sloped floors, cracked ceilings, sticking doors and broken pipes. Fortunately, building a quality foundation is easy to do. With a watchful eye and some understanding of today's reliable building materials, you can ensure that this phase of the homebuilding process ends with a solid foundation for a sound and durable home.
Before work on the foundation can begin, the building's footprint must be cleared of trees and debris. If you are building on a wooded lot, tell your builder to preserve as many trees as possible: they keep the sun from overheating your home and protect your walls from strong winds. Mature trees significantly increase property value, too.
The land must then be flattened, or graded. A good foundation is built so that rainwater flows away from the house. If not, your home will be prone to water infiltration, rot and mold.
Ask the builder:
»What is your plan for preserving trees on the site?
»How will you situate the house to avoid ponding problems?
The three common types of foundations are slab, basement, and crawlspace. They are typically built from concrete blocks or poured concrete. Consider substituting fly ash for portland cement when pouring concrete; it will improve the strength of the concrete, and offers an affordable and environmentally friendly alternative.
Slab-on-grade foundations are used throughout the country because of their low cost and relative ease of construction. Concrete is poured over the entire base of the house. Slab foundations rely on the ground to support the house, so the soil must be thoroughly compacted to minimize settling.
Basements are common in the northern and eastern states. They maximize the amount of usable space in a home. Basement walls usually double as the foundation walls. A concrete slab, which becomes the basement floor, is usually poured to connect the foundation walls.
Crawlspaces are popular in the southeast and in areas with high water tables. A crawlspace is created with an above-ground perimeter of concrete or block that holds up the home. When built properly, this foundation type tends to keep termites away. Although vented crawlspaces are common practice, experts are finding that unvented crawlspaces are more energy efficient and improve the durability of the home by better controlling moisture.
Although not required by most building or energy codes, insulating the foundation walls is a good idea, especially in cooler climates where the U.S. Department of Energy says you can save from $250-450 per year on heating bills.
Ask the builder:
»Will you insulate the foundation?
»Are you using fly ash in the concrete?
»Is there a proper foundation drainage system in place to keep standing water away from the foundation?
Precast Concrete Panels are built in a factory, where they can be made to be significantly stronger than either concrete block or concrete poured on site. A typical precast foundation is installed in about 5 hours, which is about one-sixth the time needed for a formed concrete wall. By reducing the labor and disruption at the site, the use of precast concrete panels can save money while providing an improved foundation.
Frost Protected Shallow Foundations can save money on homes without basements in northern climates. Traditionally, a foundation must be dug below the frost line, which can be rather deep, and expensive. Frost Protect Shallow Foundations allow the foundation to be dug only 12 to 16 inches below ground. Aside from the shallow depth - which is allowed because insulation is placed alongside the outside of the foundation - they are identical to conventional foundations. They simplify and accelerate the building process and can save the builder - and you - from hundreds to thousands of dollars depending on the location and the size of the house.
Insulating concrete forms (ICFs) are rigid plastic foam forms that hold concrete in place while it dries, or cures. The forms then remain in place to serve as thermal insulation. They accelerate the process of building concrete walls and foundations, and the insulation will reduce your energy bills and make your house more comfortable. Because of their benefits - including sound attenuation, impact resistance, and high R-value (link to a definition on lingo page) - ICFs are desirable in above-grade applications as well as foundations.
Ask the builder:
»Can we benefit from using frost protected shallow foundations?
»Are we getting the strongest, most durable foundation we will need?
Toolbase has a wealth of information on foundations and foundation-related issues.
Builders Web Source has a detailed overview of foundations.
Content updated on 8/7/2006
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