My plan is to turn the SE corner of the basement from a dim and dingy office/”bedroom” into a functional, bright and safe legal fourth bedroom.  For health and safety reasons a bedroom, especially one in a basement needs a window.  There was a tiny ceiling level window the the space before.  Once expanded, it now serves all those needs.Â
After a week and a half of protecting the house with just a well placed sheet of old faux wood paneling, I now have a functional window in place.
Before the window could go in, there was a bunch of concrete work to do – all the cut edges of the old concrete blocks needed to be filled in. I jammed old bits of insulation into the vertical holes to minimize the amount of mortar mix we’d need, then we mixed, poured and shaped. Â The trickiest bit was filling in the holes in the side walls – those needed some make shift “form work” of plywood to hold them – braced in place with cross braced 2x4s.
The base plate (treated) was set directly into the new mortar – a series of 3″ deck screws projecting from the bottom of the plate went into wet cement and then a mortar angled sill slopes down directly from that base.
From there we built up side panels and a top plate – also treated 2×6 – and connected snugly to the newly mortared side walls with concrete anchors. Â The top plate got two evenly spaced cripples to connect it to the house’s exciting mud sill. Â We used a construction window with a nailing fin attached on all four sides, then scored and snapped it off the bottom edge which sat flush on the base plate against a generous double bead of caulk. Â We also lined the side and top plates with caulk before installing the window and then sealed the edges again once it was in place.
I placed the window slightly lower on the wall than absolutely necessary so that it would be low enough to meet egress height requirements and to allow space above for a soffit to run continuously around the room above it. Â More on this later.
The final step was to close the gap over the window. Â I went with a PVC composite board for the window trim so that there could be no concern about rot or water intrusion. Â The outside is pretty much set for now (it needs some greenery come spring). Â Its time to turn my attention to insulating and furring out the interior of the basement bedroom.