Re-Using and Venting an Existing Foundation
I am building a 26’x36′ house at a location that is currently occupied by a 16’x36′ structure. That structure sits on a dirt-floor basement, the walls of which consist of 4′ of poured concrete that reaches to approximately ground level and ~3′ of concrete blocks on top. The site is located in the midcoast region of ME, CZ 6.
I would like to make use of the existing foundation by doing the following:
1.) Remove the concrete block, leaving the 4′ walls of poured concrete
2.) Remove the front wall of the existing foundation, extend the 16′ side walls by 10′ to achieve the 26′ depth of the new building, and pour a new 4′ tall front wall.
3.) Pour a concrete floor over the entirety of the new 26’x36′ foundation.
The 4′ tall crawl space walls would be insulated with 2″ of foam on the exterior and interior sides, 2-4″ of foam and poly would be placed under the slab. Access to the crawl space would occur via a door or trap door from the first floor and a short door (or bulkhead) into the space from the exterior of the house.
The advantages of this approach include a dry insulated storage area, access for floor plumbing and electrical work , and space for a pressure tank and water heater, while saving considerable money on the earthwork, demo, and concrete work needed to build a full basement. The lower profile of the house is also a plus IMO.
I have read about options for venting a sealed crawlspace on GBA but in many cases those articles deal with spaces with dirt floor, rubble walls, and the like (i.e. situations with high moisture potential). Insofar as I am, in essence, building a short basement, I am wondering what venting requirements apply. I have lived in various houses that were essentially sealed, save for an egress door, that did not have active ventilation. Do I need anything more in this case?
Thanks for any advice you can offer.
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