Basement wall and floor insulation, water management
I’ve spent hours reading through many of the Q&A questions regarding basement insulation and water issues and they have been extremely helpful. My house is located in St. Paul, Minnesota, was built in the 40’s and the basement has had bulk water infiltration through walls and window wells and seepage through the concrete block, resulting in the usual wetness and mold problems. The exterior is brick and in a 20’ section along the front of the house approximately 5 courses were below grade. In one rain storm water seeped through the brick, down the main floor wall and dripped through the drywall ceiling in one of the finished bedrooms. Because of this and previous water issues we excavated down to the footings last fall on approximately 2/3 of the exterior, cleaned and waterproofed the block and below grade brick (masterseal HLM 5000), applied 2” or rigid foam below grade and added exterior drain tile that was tied in to an existing sump pump. The basement has been gutted (lots of rotten and molded wood) and water seepage/droplets through the concrete block can be seen on the exterior walls next to the slab for the garage and sunroom – these walls have no exterior waterproofing. There is currently interior drain tile around most of the basement. The basement will be insulated and finished but I’m not sure how best to address the current water problems. My initial thought is to remove the perimeter concrete, apply a dimpled membrane against the walls that are currently seeping (or all walls??), lap the membrane onto the drain tile and install new concrete. Rigid foam would then be installed against the membrane (air sealed with high quality tape and foam/caulk) and the top would be sealed with spray foam that would also seal the rim joists. Some of the other Q&A’s specifically say do not install a polyethylene vapor barrier anywhere (https://www.greenbuildingadvisor.com/blogs/dept/musings/how-insulate-basement-wall). Isn’t this exactly what the dimpled membrane would be, equivalent to a polyethylene vapor barrier? If a dimpled membrane is advised should it only be placed on the areas that do not have exterior waterproofing (slab walls, 10’ area behind front step)? Should the concrete block be painted with drylock prior to insulating? Regarding floor insulation, should rigid foam be applied directly against the concrete or should a dimpled membrane be placed underneath it? Will condensation occur between the rigid foam and the concrete on the floor? Any thoughts would be greatly appreciated. Please see pictures of the basement floor plan and proposed wall assembly.