Common problems encountered during home addition projects, including structural deficiencies, outdated wiring, mechanical systems, and more. Awareness of these common downfalls will save you time during your addition project.
Even if you give careful consideration to basic design determinants and challenges your house additions may pose, it's likely that your remodeling project will hit a few snags once it's underway. Knowing ahead of time what to watch for may not head off hurdles, but at least it will help you take them in stride and perhaps build a little cushion into your budget to cover any extra costs they'll likely entail.
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.
Adding on nearly always requires adding circuits to your house wiring plans and system, and it often includes upgrading the lighting, appliances, and other electrical equipment throughout the house. Unless your system has been updated recently, you'll probably need to boost its capacity to handle the increased power load. Any new cable and receptacles you install will need to meet current safety standards, and while you're at it, it's a good idea to bring the entire system up to code.
If you're adding only one or two rooms and your furnace and air-conditioner are relatively new, your existing mechanical system may be able to handle the extra load. Sizable additions or older, simple mechanical systems are another matter; you'll probably require either a second, separate system that's dedicated to the new space, or a total upgrade that can handle both the existing space and the addition.
If your house is more than 25 years old, it may contain hazardous materials or substances that require special handling during demolition—either safe removal or permanent stabilization (sealing or isolating). One example is lead paint, used extensively until the early 1970s. Particularly hazardous to small children, fine particles of lead paint, if absorbed in the bloodstream in significant quantities, can cause irreversible brain damage. During and after removal of lead-painted surfaces, the house must be thoroughly ventilated and vacuumed. Another example is asbestos. A cancer-causing fiber, asbestos was used in numerous construction products from the 1940s through the 1960s. Examples include insulation, ceiling and floor tiles, roofing materials, and certain kinds of wall paneling. Removal requires special equipment and protective clothing, plus total evacuation of the house for several days to prevent inhalation of airborne fibers.
Before moving ahead with planning for house additions, zero in on any other problems that might develop once you begin construction. The best way to track them down is to give your house a thorough checkup ahead of time. Compile an area-by-area checklist, then examine and rate each area yourself or hire a professional home inspector to do the job for you. If you decide to handle this task on your own, be sure to wear protective clothing, including gloves and safety goggles, and keep a respirator handy to guard against breathing asbestos fibers, old paint dust, and other toxins.