Is it possible/feasible to raise a house built on a concrete slab?
Yes; it is possible. It is frequently cost prohibitive. The steps that we have used to raise slab built houses on the coast of North Carolina, USA are as follows:
- Remove all interior personal effects. Typically the contractor will provide some storage containers for the homeowner.
- Remove Sheetrock on exterior and load bearing walls up 1′ up from the floor. Removing and anchor bolts. Cut through the plumbing lines and any other through the slab utilities.
- Secure cabinets and fiberglass tubs securely to their respective walls. Disconnect the hot water heater and store if good, dispose if old. Tile showers are removed, expensive light fixtures or other easily damaged high valued items are removed for safe storage.
- Cut through exterior walls and slide steel beams through the house perpendicular to the main second floor or roof loads.
- We use 2×12’s perpendicular to and over top the beams. These are installed by using lags directing into every stud. This transfers loading to the steel evenly so there is minimal deflection between the spans. The bottom plates are crossed braced at this time also
- The house is then raised. A new foundation is constructed, and a floor system constructed.
- The house can then be lowered, and reattached to the new floor system.
- Interior finishes are completed at this time, in the same manner that they would be for any other remodel.
A side note: Although it is not usually a problem with slab houses, as the ductwork is in the attic, it bears mention. I have an associate who didn’t take this into account. Depending on the municipality, air ducts are required to be above the 12″ of free board that is required by FEMA. So if air ducts are to be installed in the crawl space if the newly elevated home, this extra distance must be accounted for in addition to the flood shot for the finished bottom of floor height. By the way, my associate had to raise the house a second time the extra two courses of block, because he didn’t take that into account. That’s an expensive oversight.