Last November, my company began remodeling a French cottage–style home in the Hudson River Valley region of New York. Built in the late 1960s, the existing wood-framed structure was set on a slab-on-grade foundation. It had half-round transoms above the doors and windows, a cementitious exterior veneer, and a hip roof with steep, unequal pitches and a curved “flare” at the eaves—all in keeping with its architectural style.
The scope of work included tearing down the existing 13-by-18-foot screened porch on the south end of the house and replacing it with a larger, 15-by-22-foot sunroom; providing a new bedroom and sitting area above the new sunroom; remodeling part of the existing second floor adjacent to the new living space; adding new dormers to both the existing and new roofs; and reroofing and re-stuccoing the entire home. In this slideshow, we’ll focus on the work relevant to the four-season room.
We broke up the job into two phases because of the late-November start date. For the first phase, our plan was to complete the demo work and foundations, then button up the place before the snow started. We began by removing the existing porch roof. It was a trapezoidal shape and had a flat top covered with single-ply EPDM. We stripped off the shingles, cut up the sheathing, and carefully removed the rafters by hand so as not to damage the main house.
Then we turned to the porch walls, which were stucco-clad. The posts and top portion around the existing half-round windows were wood-framed, with short block “knee walls” at the base. We pulled them down with the help of a skid-steer, which we also used to remove the top courses of the existing block frost wall and slab, and to help clean up the debris.
To gain an additional 100 square feet or so for the sunroom, the new frost walls were aligned with the foundation walls of the main building. We left the bottom block courses of the existing frost wall and poured footing in place, using them to hold back the soil on one side of the trench. After excavating to about 4 feet, we formed 10x16-inch (HxW) footings, ran two #4 rebar, and poured 4,000-psi concrete.
We waited a day, then formed the 8-inch-thick stem walls, which included a 3-inch-wide shelf to catch the edge of the slab. The tops of the walls were set at a height that would allow the new slab to match the finish floor level in the main house as well as maintain proper clearance above grade. We padded out the forms with 2x10s to create the shelf, ran #4 rebar top and bottom, then poured the walls with 3,500-psi to 4,000-psi concrete and wet-set anchor bolts every 4 feet.