The two main foundation types are Pier & Beam Founcations and Concrete Slab Foundations. Of the two, pier & beams foundations are generally less labor intensive to fix and are thus less costly. This is due to being able to access and work on the problem area through a crawl space.
The size and depth of the slab are determined. A concrete slab should have a minimum depth of 4 inches depending on use. For a garage, the depth should be 5-6 inches. The area should be carefully measured to final placement. The grade of the dirt also needs to be considered at this point considering the slab needs to be level. Additionally the dirt around the slab should be sloped away from the site at a rate of at least 1 inch per foot.
The dirt needs to be removed to make space for the concrete slab. Assuming a 4 inch slab, the hole should be dug to 6-7 inches to allow for backfilling of sand or crush and run.
The concrete form is made of 2 x 4's and secured with stakes. The positioning of the concrete form needs to be perfect because this will be the final layout for the concrete slab. A laser transit is used by professionals to ensure the proper height of the concrete form.
Any debris must be removed and the hole must be nice and flat. The soil should be compacted with a tamper. Sand or crush and run should be added to just below the bottom of the 2 x 4 concrete forms to allow for the proper thickness of concrete. The backfill will help with drainage and provide a good sub-foundation for the concrete. The backfill should be compacted again with a tamper.
Concrete wire, rebar and a moisture barrier can all be added at this point. The concrete wire and rebar will add extra strength to the structure and help reduce the chance of major settling. The moisture barrier will also protect the concrete from moisture below.
The concrete is poured to the top of the concrete forms and screeded and leveled off. Bolts are placed in the concrete around the perimeter to later fasten the wallplates. The concrete is edged and worked to a smooth finish. A machine is typically used after the concrete has partially dried to work the concrete to a slick finish.
There are several reasons why a concrete slab foundation could fail. It is important to both 1) Identify the CAUSE of your problem and also 2) FIX THE DAMAGE that has resulted. Common reasons for problems include:
Seasonal conditions cause the soil properties to change. When soil is full of water it naturally swells. When it dries out it contracts. The process over time undermines the integrity of the soil, and any foundation built on it. On the East Coast, namely Virginia Beach, and the Hampton Roads area, clay soils are the predominant soil type. Clay soils are the worst draining of all soil types causing a higher proportion of foundation issues.
The soil should be prepped prior to the pouring of any concrete. For a highly clay soil like that of Virginia Beach, sand should be added to facilitate drainage. Foundation contractors should also tamp the soil with a tamper prior to ensure the soil is compact as possible to reduce the chance of any settling. The soil should be even before pouring any concrete. Additionally the use of rebar and fibers can be used to further strengthen the concrete footings.
The building codes in Virginia Beach, Norfolk, and Chesapeake were much more relaxed in the past than they are now. Many homes in the Hampton Roads area were built in the 1960's - 1980's. Contractors could get away with pouring concrete without doing the proper prepwork including proper backfill, rebar, and concrete wire. Some concrete foundations were poured too thin to save money on concrete.
Water is your friend when you are drinking it or when you are taking a shower, but it is your enemy if it gets under your home. In some cases, busted plumbing under the soil compromises the soil and the foundation. Most commonly, the yard doesn't have proper drainage. The ground surrounding your home should be graded/sloped away from your home to allow the water to drain. If the water is pooling around and under your home, you have a problem you need to fix immediately before the damage is done.
Continue Reading: Concrete Slab Foundation Repair
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Foundation Contractor in Virginia Beach specializing in house leveling, slab jacking, installation of additional crawlspace piers, slab repair and all other structural repairs in Virginia Beach, VA