Posted on January 14th, 2016 by Aaron Presley
Certain geographic areas present unique challenges when building a home. In areas that are prone to flooding, that have loose or sandy topsoil, or that are swampy, house pilings are often driven into the ground to reach more stable soil or bedrock, and the house is constructed on top of the pilings. This raises the house above the typical flood line, protecting it from damage during major storms or other flooding events.
House pilings are also used in some areas where the bedrock is near the surface, and it would be less cost-effective to dig a traditional footing and foundation. Instead, holes are drilled down to the bedrock or into it, in some cases, and house pilings are inserted to support the structure of the home.
In order to function well, house pilings must be strong, durable and able to withstand the elements, including wind, rain, snow and UV radiation. They must also be able to resist damage from insects, fungus and other organisms that cause wood to deteriorate, eventually leading to structural failure.
Here are a few of the things that should be considered when purchasing house pilings:
#1 Location Characteristics
The conditions at the building site need to be analyzed to determine the type of house pilings that will be needed. The amount of moisture will affect the choice of chemical treatments that are used to protect the wood, with drier areas requiring a lower concentration of preservatives, typically chromated copper arsenate, alkaline copper quaternary or copper azole, and moist areas receiving a higher concentration. Areas that are exposed to salt water or that have a healthy population of pests like termites or carpenter ants may require alternate formulations. The location will also help determine the length that the pilings that must be driven into the ground, as well as their size and spacing.
#2 Home Design
The size, structure and design of the home will be a major factor in determining the type of pilings needed for the project. For houses in major flood areas, like the Gulf Coast, longer pilings are necessary to raise the home the necessary height, often a full story above the ground. Other areas may need to only raise the structure a few feet, in addition to the length that the piling will be driven into the ground.
To provide the proper amount of support, the structure of the home will have to be considered. Single story small homes can use less expensive pilings with a smaller diameter, while larger homes or heavier two-story buildings will require either large-diameter pilings, or a series of smaller pilings placed closer together. This will depend on the structural requirements of the building, the site conditions, the cost of the pilings and the installation costs.
House pilings are typically available in three cross sections, including standard round pilings, uniform-diameter pilings and square pilings. Standard pilings have a shape that is generally round, but due to natural variations in the wood, it will not be perfectly round and it will taper from one end to the other. These are the least expensive, but they may require some extra work to line them up properly and account for the natural variances so that the resulting structure is level, plumb and square. They have the most protection for the vulnerable heartwood that is at the center of the piling, which is softer and more prone to rotting or being preyed upon by insects.
Uniform-diameter pilings have been machined on a lathe to obtain a perfect round shape with a continuous diameter from one end of the piling to the other. These are easier to work with than natural pilings, but they are more expensive, and they may leave the heartwood more vulnerable where the natural tree was narrower.
Square pilings have been cut to create a square cross-section, which is more aesthetically pleasing and easier to work with than the round pilings. The significant milling required to to create the square shape, however, leaves much more of the heartwood exposed.
During flooding, the round pilings stand up to the force of water and debris better, because the shape does not inhibit the flow as much. Square pilings can create turbulence in the surrounding water, with significant high and low pressure areas, making them more likely to suffer from erosion and debris damage.
#4 Moisture Resistance
Constant exposure to moisture can soften wood and leave it vulnerable to fungus growth, insect damage and other processes that slowly rot the wood away and leave it prone to structural failure. By using a process that forces chemical preservatives deep into the grain of the wood with high amounts of pressure, house pilings can be treated to withstand different levels of moisture exposure. They can be used in areas with dry soils, or ones that are consistently moist. Some formulations are designed to protect from occasional exposure to salt water, for areas near the ocean, and, with higher chemical concentrations, some house pilings can even be used where they are permanently immersed in either fresh water or salt water.
#5 Insect Resistance
Some areas have large populations of wood-boring insects, such as termites or carpenter ants. These insects can cause significant amounts of damage in a short amount of time, and they can also lead to dangerous structural failures. By burrowing into wood beams and joists, they can make them nearly hollow and unable to support significant amounts of weight. House pilings in infested areas are available with several types of insecticides, such as borate, which not only prevent damage to the pilings themselves, but also discourage the insects from venturing into other areas of your home.
By selecting house pilings with the correct chemical treatments for the area, and taking into account factors like the structure of the building, you can build confidently, knowing that the structure will withstand the forces of nature and last for many years to come. In addition to building a home, house pilings with the correct chemical treatments and specifications can also be used for structures such as docks, piers, pole barns, light poles and many other projects where the structural elements are exposed to the environment.