Does a crawl space save money?

            When you compare a full foundation to a crawl space it looks like there is a substantial cost savings.  In reality there are many things to consider.  Yes, the excavation may be cheaper since the foundation hole is more shallow.    There may also be less backfill required with a crawl space depending on how deep it can be excavated.  Lastly,  there is less concrete needed.  But there are many other factors that should be considered.

            With a crawl space the concrete floor is often omitted because of cost.  The concrete slab contains the vapor barrier, so without it moisture has to be dealt with.  This usually means a continuous vapor barrier down the walls and across the floor, and it has to be protected from punctures somehow.  Additionally this space has to be ventilated to protect the framing from rot.  Placing a bed of sand below polyethylene and above it is usually the easiest way to protect it,  and  foundation vents or a vent stack is often used to ventilate it.  Access with a crawl space is also difficult.  When building a house this means a lot of additional labor.  All of the building mechanicals are often run in the basement, so many more man hours are consumed just because of poor access.

            The payback storage cost is by far the biggest factor.  When the home is built on a crawl space it doesn’t provide any storage space at all, therefore accessory buildings are eventually built.  This future expense compounded with the extra construction labor for the mechanicals can offset the initial cost of a full foundation.  Assuming the site conditions will allow it,  a full foundation is the cheapest square foot cost of a structure.

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