Basement Glass Block Replacement Installation
I am an experienced DIY-er hoping to leverage some expert knowledge for a window installation. My recently purchased home is from 1955 with a block basement. I would like to replace all of the the basement windows (below grade, inside a well, no egress currently or needed).
I ordered one preassembled glass block window from Lowes that is slightly smaller than the wall rough opening. The instructions that came with the window are pretty self explanatory but they do not touch on three questions that I need to resolve.
1. Is there any prep on the existing block that should be done before mortaring the windows in?
2. The top of the rough opening is not masonry, but is instead the sill plate of the house. Can/should I create a mortar joint directly against this sill plate, or should I be prepping this somehow also?
3. This is my most pressing concern and question. The bottom of the rough opening has been raised and tapered to a point of sorts. I believe this may be called a cap? Please see attached photo. The top of this cap on the flat is no more than 1″ or so wide (the metal frame of the existing window sits perfectly flush on the edges of this cap. The new glass block window, however is 3″ thick. So at this point, if I install the window without altering this cap, I would have about an inch of the lower part of the window on both the inside and outside of the that would not look right to me.
At this point, the window is already purchased and delivered to size. I really don’t want to cut part of this cap to create a wider base and reorder a taller window. So these were my two thoughts I was having to resolve this issue:
Install the window with it sticking out an inch at the bottom (inside and outside of the basement opening) and try to create a large mortar joint that will be flush with the window bottom.
Or fabricate a two small forms and affix them the the bottom of the rough opening after removing the old window. I would fill these small forms on either side of the cap to level it out. After it dries, remove them and proceed with the window install.
Any expert opinions would be greatly appreciated.