Question: Is there any benefit to using lime in a crawlspace other than for odors? Is it a deterrent for spiders, snakes, mice, etc.? What type of lime is used? If it goes under the vapor barrier, won't the moisture from the ground mix with it and produce heat that will ruin the vapor barrier's effectiveness?
Answer: Crawlspace odors are usually caused by a leaky sewer pipe, damp fiberglass insulation, dead animals, mold, cardboard and debris, to name a few possibilities.
Lime powder, found at home stores, garden centers and some pet stores, can be used to absorb strong odors that might be coming from a crawlspace. An additional benefit of lime powder is that it dehydrates and suffocates insects that come into contact with the powdered form of lime.
Calcium hypochlorite can also be used as a disinfectant, but this form of lime, found at pool dealers, can become unstable when exposed to air and moisture. Calcium hypochlorite lime creates heat as it off-gases chlorine gas, which may not be suitable when confined to a crawlspace.
Spread the powdered lime on top of the existing vapor barrier, adding more powder after a few days if the odors persist. Once the odors have dissipated, remove all the old vapor barrier and lime. Remove all debris and vegetation and then install a new 6-mil-or-thicker black or clear vapor barrier, securing it to the crawl floor with bricks, stones or vapor-barrier pins.
You should also consider a product called CleanSpace, which is a 20-mil-thick white liner that encapsulates the floors and walls of a crawlspace foundation, eliminating virtually all possibilities of ground moisture reaching the floor system of the home.
Where there is no moisture, you have essentially eliminated all possibilities of decay and odors. It is imperative that a crawlspace have a secure, insulated access door to prevent pest entry and to conserve energy.
(Dwight Barnett is a certified master inspector. Contact him at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 268, Evansville, IN 47702 or firstname.lastname@example.org.)