Rob Shuman has plans to build a 26-ft. by 36-ft. house in Midcoast Maine to replace a smaller structure already on the lot. That sounds straightforward enough. The only wrinkle is that Shuman wants to use the existing foundation for the new house, and it’s currently about 10 ft. too small.
As he explains in this recent Q&A post, “I am building a 26-ft. by 36-ft. house at a location that is currently occupied by a 16-ft. by 36-ft. structure. That structure sits on a dirt-floor basement, the walls of which consist of 4 ft. of poured concrete that reaches to approximately ground level, and about 3 ft. of concrete block on top.”
His plan goes something like this: remove the concrete block and leave the concrete stem walls, remove the front wall of the foundation and extend the walls by 10 ft., then pour a new 4-ft. front wall. A new concrete slab would cover the entire 26-by-36 ft. floor of the enlarged foundation.
Shuman would insulate the concrete walls with 2 in. of rigid foam, with another 2 to 4 in. of foam under the slab. Access to the crawlspace would be via a door on the first floor and a bulkhead from the outside.
“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,” he writes, “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, in my opinion.”
He’s especially concerned about venting the space. “Insofar as I am, in essence, building a short basement,” he adds, “I am wondering what venting requirements apply.”
Is this solution brilliant green recycling or prone to problems? That’s…