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Laying the Foundation - TYPES OF HOME FOUNDATIONS

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by Allison Gunkel

Home building discussions often span many topics from basic home decor schematics to hardware and appliances.

Home Foundation

Home building discussions often span many topics from decorating schematics to hardware and appliances. However, a very important decision that should be made first is what residential foundation type will be laid for your home. The simple definition of foundation is the portion of a building's structure whose purpose is to transplant the weight of the building into the ground. Sounds simple, right? One may not realize that something so basic and essential has so many options.

Before delving into the different types of home foundations, there are some requirements that apply to all foundations, from the smallest garden shed to the largest sprawling villa.

  1. Ability to hold the house up –
    Many of today's foundations are over built to support the load of the house constructed upon it. However, it is vital that the load does not exceed the foundation's bearing capacity – the foundation is guaranteed to fail if this happens. Foundations must also be placed on undisturbed soil that will not considerably deform over time, as this will cause problems and damage in the future.

  2. Keeping the ground water out –
    The main cause of damp foundations is ground water that finds its way where it ought not to be. The solution may be simpler than you think. An obvious choice is to build on a hill, that is, slope the ground away from the foundation and let gravity take its course. Another solution is efficient gutters and downspouts that direct roof runoff clear of the structure. Drainage material such as sand, gravel, and other porous substances allow water to pass through rather than pool up, directing excess moisture away from the foundation. Waterproof seals are not a solution to a bad drainage system. Good drainage combined with waterproofing can ensure long lasting moisture protection.

  3. Blocking soil gas/water vapor -
    Installing a subslab drainage pad is another way to keep moisture out away from the foundation. Placing a layer of polyethylene sheeting between the drainage pad and the foundation blocks water vapor from permeating the foundation and causing indoor air pollution. That same drainage pad keeps unknown soil gases from hurting indoor air quality also. When building a home, it is difficult to know what your soil has been exposed to. Taking measures like these will ensure these potentially harmful materials cannot find a means through your foundation into your home.

The residential foundation type you choose will depend largely on the region in which you are building, your specific lot of land, and your budget. Consulting with your contractor before any construction begins is an absolute must. The contractor's suggestions should be carefully considered; do not hesitate to ask why a specific foundation is recommended. If you are unsure about the recommendation, take the time to consult with a number of area contractors and see what the consensus is before you go on building something that you may not want, or may not actually be good for your home.

Slab Foundations

A slab foundation is a foundation built directly on the soil with no basement or crawl space. The build site is leveled and a trench is dug around the perimeter. Gravel is spread across the site and concrete is poured approximately four inches thick over a mesh and moisture barrier layer. The trenches that were dug allow concrete to be poured where the load bearing walls are placed, providing additional thickness and support. No piers or joists are used, as this foundation transfers the weight of the building directly to the soil via the slab.

Slab foundations are popular among builders and homeowners alike for their relatively low cost, minimal excavation needs, and the fact that slab foundations tend to accelerate projected construction schedules. However, the lack of basement or crawl space provides minimal protection from fierce storms. Plumbing and heating and cooling systems are all buried beneath the slab, so should issues arise, repairs are often costly and time consuming. Insulation precautions must be carefully taken with the knowledge that thermal conduction issues almost always arise. Similarly, protection from moisture and runoff damage must be taken seriously as the home sits closer to the ground than with other foundation types.

Crawl Spaces

A crawl space foundation is one where the footing is poured as well as short foundation walls to support the home. These are very short walls, some only 16-18 inches deep. This foundation will save you slightly in cost, however there is no time saved in comparison to other foundations. Crawl spaces keep the utilities accessible (as long as you do not mind being on your hands and knees). Insulation of the interior walls and the ceiling of the space is usually needed, as this is the floor of the home above. A vapor barrier over the soil of the crawl space also is recommended to defer mold issues. Crawl spaces eliminate many of the issues found with slab foundations; however, they still offer very little protection from storms.

Concrete Foundation for Home

Basements & Walk-Outs

All buildings have footings that anchor the structure into the ground. These footings have to be extended below a region's frost line in order to avoid damage that could compromise the integrity of the structure. In cold climates, where the frost line is quite deep, you find that many homes have basements. After all, if you are already digging deep to support your home, for a minimal additional cost you could add another living space. Many homes that do not have to dig deep for the footings are including basements in their plans as they are extremely functional and worth the money.

Basements are idyllic for storage and for easy access to mechanics. This aids to the proper maintenance of plumbing and heating and cooling systems. Basements also can be finished as extra living spaces that stay nice and cool during hot weather (great for wine cellars and home theaters) and include installed safe rooms for storm protection. Small lot homes especially appreciate the additional space a basement can provide, both in storage capacities and living space.

Some drawbacks to basements are the lack of natural light, the humidity that is simply a fact of nature, and the accessibility issues. Without natural light, some basements feel stuffy or uninhabitable. But this can be combated by walk out basements installed on sloping lots as well as daylight basements that allow some light access via small windows. Humidity is always present in basements and can be minimized by dehumidifiers and waterproofing. However, it is necessary to continually keep an eye out for mold or mildew so as to not compromise the air quality of your home. Since stairs access most basements, utilizing the basement as living space is not always a viable option for those with additional mobility needs.

Pier Foundations

Pier foundations use small square or circular pads of concrete located at strategic points around the outer perimeter of the building. These pads are placed into the ground with vertical posts of treated wood or steel connecting to the underside of the structure via horizontal beams. These beams support the floor joists and exterior walls. This type of foundation is necessary to use on lots where traditional foundations are difficult to lay. For larger structures, more pads and posts may be placed inside the outer border for additional support.

Any residential foundation type you choose, as long as it is properly installed, will serve your home well. Discussing the options for your home with your contractor is the best place to start to ensure that what you have in mind can be done. If you have future intentions for your home, such as add-ons, basement refinishing, additional porch space, etc, bring these ideas into the beginning conversations so they can be taken into consideration when planning the base of your home.

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