One of the common questions we receive at UDA concerns whether a basement foundation is appropriate for an individual building site. To help you make the best decision, we have outlined the requirements and considerations necessary when deciding on a basement or other foundation type.
1. Site Conditions
The grade or lay of your lot will have a significant impact upon the suitability and location of a basement. Typically you will need a 6' to 10' dropoff in elevation height from side to side or front to back to accomodate for an appropriate walk-out basement. Lots that are lower in the front present unique considerations such as basement windows on the front of the home and/or excessive steps to access the front door. Other important factors that will contribute include subsurface water table level, flood plains and excavation. ( extensive surface rock usually indicates subsurface or hidden rock that could add significant expense )
2. Walkout or Cellar Type
By identifying the actual building corners and measuring grade elevations using a surveyors level or transit you will be able to determine if the lot you are considering will accomodate a walk-out / daylight basement ( a basement that has doors and windows to the exterior ) or if a cellar is a viable option in your region.
3. Exterior Walls
Exterior walls for basements can be
constructed from a variety of materials, typically 8" x 16" or 12" x 16"
concrete block ( CMU ) reinforced with poured concrete cells and reinforcing
steel ( rebar ) or 8" to 12" thick solid concrete poured walls. Both
systems will require an appropriate tar or rubber based waterproofing and
drainage system to function properly. Several alternate materials have
been introduced that offer additional features such as EPS ( expanded polystyrene
) interlocking blocks, etc. We will further discuss these new materials
in an upcoming eNewsletter.
Beyond the obvious structural considerations, proper drainage is the critical link in establishing and maintaining a dry basement. An appropriate system will provide positive drainage of any standing water adjacent the exterior surface of the basement wall by filtering hydrostatic water pressure through gravel to a french drain or perforated pipe at the base of the wall. If silt or clay is present you will want to wrap the drain pipe with a geotechnical fabric or silt fence that will keep the pipe from clogging up. The end / low side of the drain should be left open to drain freely. Cellars might also include a drain located within the slab that is emptied by a automatic sump pump.
5. Interior Structure
We always recommend that basements are built with a minimum 9'-0" ceiling height so that after dropping the ceiling for any mechanical systems such as HVAC ductwork / plumbing you will still have a minimum 8'-0" ceiling height. Interior structure can consist of loadbearing walls located directly under the main floor bearing walls or through a system of adjustable steel columns.
6. Cost Considerations, Plumbing, HVAC
If your lot will allow, basements can provide very cost effective square footage for enlarging the living space or storage area of your home with savings of $20 to $40 per square foot as compared to the rest of your home. For example, an unfinished basement might add additional costs of approximately $12 -$28 per square foot to the home, significantly less than expanding the first floor. If you are planning on finishing the basement at a future date, you will need to rough-in any plumbing, specifically drains located within the concrete slab. Depending upon your time-frame and local weather requirements consult with your HVAC contractor for options on heating and cooling your basement.
Standard and Custom Basement Foundations are available for most UDA Ideal Home Plans and Duplexes. For further information consult UDA Plan Modifications or contact UDA Customer Assistance toll-free 1-800-700-8321, M-F 9-7 EST
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