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Underneath It All

Setting your cabin on a firm foundation.

Setting your cabin on a firm foundation.

100_6922 There’s an old proverb that says “well-begun is half done.” For your construction project to be well-begun and on its way to a successful finish, it needs to start with a stable, well-built foundation. Foundations are built in a variety of ways, depending on a range of factors. As you begin designing your new cabin, discuss with your designer or builder the foundation that best suits your project. You and your building professionals will consider foundation construction methods, local building codes and other factors. Your Site The climate in your area affects how deep your foundation needs to be excavated. The condition of your particular property could impact the design of your foundation. Is it too rocky to excavate? Is the soil stable? How deep is the water table? Does the site slope steeply? Take a look at the types of foundations used in other homes in your area. If concrete slab foundations are prevalent where you’re building, it’s a viable option for you. Otherwise, your cabin could require a fully excavated foundation. In colder climates, the top of the footings for the foundation must be below the frost line. This depth will help avoid movement of the foundation during freeze/thaw cycles. The frost line depth varies according to region: It’s closer to the surface in warmer climates. Your Cabin’s Purpose A small, seasonal cabin could be built on piers that support the cabin in the corners and along spans of the floor framing. If your cabin will be more than a place to spend a few weeks’ vacation, you will most likely look into a poured cement or cement block wall foundation. How often you use the cabin and how much storage you need could factor into your decision to choose a full-height basement or go with a crawl space. A crawl space can accommodate ductwork and heating and water heating equipment. Crawl spaces also offer the advantage of lifting a house up off the ground to help avoid termite damage. Full-height basement walls are more expensive to build, but do result in a lower level that provides space for storage and utility equipment. It could also potentially be used as living space. Building the Foundation The most common foundation for North American homes requires a poured footing topped with walls of poured concrete or stacked concrete blocks. Slab on grade foundations are found in some areas. All of these foundations start with site work. Once a building site is cleared, it’s surveyed and stakes are placed, marking the dimensions of the home. Excavators dig out an area larger than the house measurements to allow for the crew to build the foundation. Top layers are removed to reveal solid, compact soil. For a slab on grade foundation, excavators dig trenches for footings. These trenches will be outfitted with drainage systems to move water away from the foundation. Before the concrete slab is poured, the area may be layered with gravel, a vapor barrier, sand, reinforcing mesh and insulation. Radon gas evacuation systems (if necessary) and utilities are roughed in before the slab is poured. If a home will include a radiant floor heating system, the tubing for that system is set in place as well. Finally, the concrete slab is poured in place and made ready to be the base for the home’s walls. If the foundation will include a crawl space or full basement, footings are built. These poured-concrete footings help distribute the weight of the foundation walls to the site’s soil and help resist sinking or shifting. They are generally wider and longer than the foundation wall. At this point, drainage tiles or systems may be installed to keep water directed away from the home’s foundation. The foundation walls are built on top of the footings. Concrete may be poured into forms that are built on the footings and studded with rebar to give the concrete added stiffness. When the concrete cures, these forms are removed. For concrete block walls, the blocks are stacked and mortared in place on top of the footings to the desired height. Once the walls of the crawl space or basement are complete, waterproofing treatment is applied to the exterior. Some homeowners may choose to have their basement walls insulated on the exterior at this point as well. Then, a concrete slab may be poured into the base of the foundation, to create the basement floor. This final slab may not be poured until after the home construction is begun, and will be set on top of layers of gravel, vapor barrier, insulation and reinforcing wire mesh. For crawl spaces, steps should be taken to prevent moisture from the crawl space wicking up into the home’s wood floor beams. Talk to your builder about the best way to keep your crawl space warm and dry in your climate. The walls of the foundation are backfilled to give them added stability. This fill should be graded to encourage water to flow away from the house. Insulated and Precast Walls Some homeowners choose insulated concrete or precast walls for their foundations. The insulated forms, faced with foam, are set in place on top of the footings and filled with concrete. Unlike traditional forms, the insulated forms are left in place to provide an envelope of insulation around the perimeter of the foundation, making the home more energy-efficient. The foam on the interior of the foundation wall can be finished with drywall or any other common wall facing if the basement will be used as living space. With precast wall construction, sections of foundation walls are built to the home’s exact specifications in a manufacturer’s facility, then delivered to the construction site. This construction method cuts down on the time required to build the foundation. Precast walls may be purchased with or without insulation.

The Finished Basement

montana with windows in basementWhen building a new home, remember that a finished basement can provide plenty of living space with a reasonable price tag. With proper waterproofing, your basement space can be dry, comfortable and ready for you to enjoy. The Concrete Network (concretenetwork.com) suggests considering these issues with a finished basement:
  • Stair location: A central staircase, instead of one placed along a perimeter wall, could cut the usable basement space in half. Consider, too, how visitors will get to your basement: Should the stairs lead down from the kitchen? From a more formal entry hall? The great room?
  • Stair design: If you want your finished basement to feel as homey as the rest of the house, make the stairs as attractive as possible. Stairs with hardwood and turned rails can help the lower level match your main floor living areas. Windows: Natural light streaming through windows that are similar in size and style to the rest of the home will make your basement more appealing.
  • Artificial light: Recessed lighting, track lighting, table lamps and accent lights all can bring life to a lower level. Put these lights on dimmers to give your finished basement extra versatility.
  • Quality finishes: Choose paint, flooring, fixtures and furnishings that will stand up to the activities you have planned for your basement. Will the space be used infrequently as a guest suite or every day as a home office or recreation room? Choose your finishes accordingly.
  • Outlets and utilities: Think through placement of electrical outlets and switches, HVAC ducts and the entrance to the utility room.
  • Ceiling height: Higher (9- or 10-foot) ceilings make a lower level more livable.
  • Fireplace: Even if your budget doesn’t allow a fireplace now, installing a flue in the basement when you build gives you the option to add one later.
  • Walk-out: Many cabins take advantage of a sloped site to create a lower level with lots of light and easy access to the outdoors.