Do You Put DPC Under The Window Sill?
Do You Put DPC Under The Window Sill?
No. Only the sill and inner wall/sill need DPC. The old sill isn’t needed. This is because a sill that has the potential to be damaged is needed to support the weight of a window. By fully supporting it, you are allowing it to hold up the weight of the window.
For safety reasons, when installing wood window sills, we highly recommend still using a sill plate for support since you can easily damage the wall below this with a falling window, especially if you have hardwood floors. Your peeling and rotting windows are more obvious with a wood sill without these plates.
The exterior wall and/or I-joists should be flashed where they contact the new construction. The exterior wall cavity should be packed with fiberglass insulation to R-19.
You need to replace all of the existing framings through 2 courses of brick (approx. 3″) and install a water-resistant barrier on all interior surfaces; including sheathing, subfloor, drywall, etc. Tighten all floor joists that are attached to these exterior walls with wood fasteners that are 1/2″.
If there is no draft guard, you will need to install one or an extension of the same material onto your new wall. The windowsill is considered part of the building envelope and should be constructed using as described above.
It’s a good idea to check with your local building department before putting in a new sill made of wood. For example, in some areas, you need to adhere to how wide apart the studs are or how far from the wall your window needs to be measured from so that it doesn’t violate any codes.
