I read your stone foundation article when looking into finishing our basement. In your experience, is a finished basement in an old house just a really bad idea?
In my experience, most "finished" basements under old homes are musty, dungeon-like spaces with delaminated paneling and moldy, sagging drop-ceiling panels. Today there are new products that, combined with proper planning, preparation and implementation, could create a pleasant, more useable space under the house.
Most old homes are built with stone or brick foundations, without waterproofing material applied below ground. Even older concrete block foundations, with original waterproofing and drain systems, can become quite damp after many decades.
To reduce the moisture penetrating these old foundations, be sure to maintain your gutters and extend downspouts well away from the foundation. Also be sure the grade slopes away from your foundation on all sides of the house and any surfaces that collects water, like patios, also slope away. If you've ever experienced water entering your basement, there are probably bigger issues to tackle before considering spending money on basement finishing.
Even if the basement seems dry, materials for finishing that are in contact with, or even near masonry, could attract condensing moisture. Even a little moisture might be enough to allow things to start growing. Where wood framing contacts masonry, appropriately treated wood should be selected. I suggest using mold and mildew resistant drywall for the walls. Vapor barriers and insulation should be correctly installed. For flooring, there are basement subfloor systems available that create an "air gap" below the floor with corrugated or cleated plastic panels that are usually 2 x 2 foot interlocking panels. The plastic also acts as a moisture barrier to help keep the finished floor dry.
Old stone and brick foundations eventually need maintenance. Any maintenance should be performed first. Finished walls close to the foundation may eventually need to be opened up during the home's history. Maybe by that time, the house will be ready for remodeling. However, I like to build things as if they'll be there forever. If you can't build the finished walls far enough away for access, there are wall panel systems manufactured for finishing basements.
There's often important stuff above basement ceilings that need periodic attention and sometimes urgent repair. Plumbing shut-off valves and clean-outs, electrical connections, and heating duct dampers are some of the items that should be readily accessible. The first-floor structure above the ceiling should be inspected periodically for wood-destroying insect infestations. Installing a suspended ceiling grid with drop-in panels can allow access above the entire ceiling. Today, there are many types of ceiling panels with dimensional designs that can be quite attractive, unlike the Styrofoam panels of the 1970s.
Health and Safety
In addition to the moisture (mold) concern, another air quality issue is radon. Radon levels are likely to be higher in a basement, where finishing usually means the family may have longer times of exposure. A simple test and mitigation, if necessary, can be easily performed before the finishing work begins.
In previously finished basements, I frequently find sub-standard and unsafe electrical work. Rarely are municipal permits and inspections obtained for work in a basement. It is often the homeowner or the remodeling contractor, who are not licensed electricians, doing the installation. This phase of the project is really something that should be done by an experienced professional.
Many old basements are only accessed by interior stairs from the main level. The new living space should really have at least one "emergency escape and rescue opening" to the exterior. If there will be a separate space that is used for sleeping, it needs its own opening. Check with your local municipal code office for required dimensions and locations.
Smoke and carbon monoxide detectors, adequate ventilation, and clearances to heating equipment also need to be considered. I'm sure you will want that extra living space created under the home to not only be pleasant, but healthy and safe too.
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