Common questions about crawl spaces
- Can ‘dormant’ mold spores appear and affect a crawl space?
- Can I use plastic sheeting as a vapor barrier?
- Can you build a pole barn house with a crawl space?
- Crawl space is infested with mold, how do we go about properly fixing it?
- Does crawl space encapsulation increase home value?
- Does encapsulating a crawl space really work and is it worth the money?
Lexington crawl space encapsulation — local context
Encapsulating a Lexington crawl space means sealing it with a 12-mil wall / 20-mil floor vapor barrier plus dimpled drainage matting, a dehumidifier, and a sump — not a loose plastic sheet. That matters here because Lexington's water table is shallow: the U.S. Geological Survey's monitoring well in town (MA-LTW 104) is just 20.7 ft deep and screens an unconfined glacial-deposit aquifer, so groundwater loads crawl spaces from below. The crawl space is also a soil-gas path, and Middlesex County sits in EPA Radon Zone 1 (predicted indoor radon above EPA's 4 pCi/L action level). Massachusetts even requires new one- and two-family Lexington homes to be built with passive radon controls "regardless of the radon levels at the site" (780 CMR Appendix AF §AF101.1). With over 50% of Lexington homes built before 1960 (Town Comprehensive Plan), fieldstone foundations and dirt floors are common — our specialty. Crawl space encapsulation runs $3,000–$25,000; radon mitigation, if needed, is a separate $1,950–$2,250 add-on. See our crawl space services or radon mitigation.
What a recent customer said
Gerald and his crew did an excellent job, first cleaning out all the debris and the dislodged insulation in the crawlspace. they were very communicative and understood my concerns and handled them professionally. When they were finished laying the sublayment and the top vinyl covering, carefully taping all the seams they put insulating foam around the perimeter, sealing the top of the vinyl. Gerald communicated two issues that were not part of the contract that I will subsequently take care of myself. Great job, very satisfied. — Alex C Arcisz, 5★
Frequently asked questions
Is radon a concern for crawl spaces in Lexington, MA?
Yes. Lexington is in Middlesex County, which the EPA Map of Radon Zones lists as Zone 1 — the highest-risk tier, with predicted average indoor radon above EPA's 4 pCi/L action level. A crawl space is a direct soil-gas entry path, so encapsulating and sealing it reduces that pathway. If testing shows elevated radon, mitigation is a separate add-on (typically $1,950–$2,250) on top of encapsulation.
Do new homes in Lexington legally need radon controls?
Yes. Because Lexington is in a high-radon-potential county, the Massachusetts State Building Code (780 CMR Appendix AF §AF101.1) requires every new one- and two-family home to be built with a passive radon-control system "regardless of the radon levels at the site." That requirement applies to new construction; for existing homes, encapsulation plus optional active mitigation is the practical retrofit.
Why do so many Lexington crawl spaces have moisture problems?
Two local reasons. First, groundwater sits shallow — the USGS monitoring well in Lexington (MA-LTW 104) is only 20.7 ft deep in an unconfined glacial-deposit aquifer, so soil moisture readily reaches crawl spaces. Second, over 50% of Lexington homes were built before 1960 (Town Comprehensive Plan), and older New England houses often have fieldstone foundations and dirt-floor crawl spaces that wick moisture. A full 12-mil wall / 20-mil floor barrier with drainage matting, a sump, and a dehumidifier addresses both.
Crawl Space Encapsulation in nearby New England towns
More 603 services in Lexington
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- Radon Mitigation in Lexington, MA