Q.My husband and I are getting ready to build a new house, and the builder is really pushing us to simply pour a concrete slab directly on the soil. I feel uneasy about this for any number of reasons. The builder says it will be cheaper and that Im needlessly worrying. What would you do, and why? Donna S. Orlando, Fla.
A. I can understand why your builder is pushing for a slab-on-grade solution for your new house, as your water table is so high in the sandy soil of Florida. But the builder may be blind to at least one other option that has been around for many years. In fact, I would be willing to bet that within one or two miles of your downtown area, we could find several houses that are 50 or more years old and are not built on slabs placed directly on the soil.
The older homes we would discover would undoubtedly have a raised wood floor system. The original builder or architect of these houses probably cleverly disguised the fact that they are sitting up off the ground 20 or 30 inches.
I love concrete and think it is a fabulous building material, but I would never personally own a house that is built on a slab. There are several reasons for this. First and foremost, I want to be able to have complete access to all plumbing, electrical and mechanical systems in my house.
Houses built on slabs, at the very least, have the plumbing drainage system buried under the slab. In some instances, heating ducts and some electrical cables are also buried. In a house with a raised wood floor system, all mechanical systems are readily visible and almost always accessible.
Besides increased functionality, a house with a raised wood floor system simply looks better than if the same house were built directly at grade level. The wall area of the raised foundation helps to give the home both stature and balance.
Houses that can be built with raised foundations in areas where basements are possible allow basement windows to be placed above grade. Windows placed above grade permit the maximum amount of available light to stream into the lower basement space.
People who live in areas where expansive clay soils are especially troublesome can really benefit from raised wood floor systems. Pier and beam foundations can be used that bypass the pesky clay soils that often cause significant cracks in slab-on-grade houses. Slabs can be engineered to resist expansive clay soils, but if the workmen dont build the slab exactly right, the best intentions of the engineer become worthless as soon as the soil expands or contracts.
Another often overlooked benefit of raised wood floor system construction is a savings for those who live in flood plain zones. You can often build in these designated areas, but if your first-floor level is exactly at the elevation of predicted floods, you pay a steep flood insurance premium. But for every foot you raise the floor level above the projected flood level, flood insurance premiums significantly decrease.
The savings over time can be dramatic. But in addition to those savings, imagine the peace of mind knowing your house stayed dry during a flood while a neighbors house built on a slab might have had 28 inches of murky polluted water invading his house for days.
There isnt much of a cost difference between building a raised wood floor system house or a slab-on-grade house. If a builder were to do an accurate labor-and-material cost comparison for an average home, the extra cost of a raised wood floor system probably wouldnt exceed $1,500. Yes, it is more money, but that extra cost buys you numerous advantages as well as increased curb appeal.
Some opponents of raised wood floor system construction say it is too difficult to go up and down steps to get into and out of the house. It is very easy to grade the exterior of the ground around some of these houses to create a gently sloping landscaped berm that serves as a pathway to the front porch so that only one step is required to enter the home.