Common Addition Problems

Structural Deficiencies in House Additions

As a general rule, there are two types of structural problems that crop up in an addition project. One type involves additions that rest on existing house foundations. Examples include bump-outs, upper-story additions, and ones that replace existing extensions (such as a porch, garage, or storage shed).

Bump-outs put extra stress on one particular section of a foundation. If the material used to build the foundation is in poor shape or if the ground underneath it is unstable, cracking or heaving could occur. One remedy is to add piers outside to help support the extra weight. Another is to reinforce house foundations with steel bars or rods. Some single-story homes and most types of extensions are built on concrete pads with shallow footings around the perimeter. This kind of system isn't designed to handle the extra weight of an upper story. Where houses are concerned, substituting stronger footings isn't a practical solution; a more sensible strategy is to add a post-and-beam system to support the upper level independently. As for extensions, it's usually necessary to remove the old footings altogether and build a proper foundation from scratch.

The other common structural problem involves floor framing for upper-level additions. The ceilings in many single-story homes are framed with 2x6 or 2x8 joists that, depending on the span, can support themselves plus drywall and insulation but may not be strong enough to support an upper floor without bouncing or sagging. The simplest remedy is to "sister" additional joists onto the existing joists to beef up the system before the subfloor for the new level is laid.