I need to replace a few basement windows in an old home.
The house has a rock wall foundation with a thick covering of cement on top and both sides of the area the windows are mounted with the top of the window in contact with the wood of the house.
The current wooden windows are badly rotted from now resolved water problems and the cement they were attached to is crumbling.
I suspect I will need to choose a window size that is close to what I need and build up a layer of fresh mortar in the area to fit the window into but I have never seen how basement windows are installed.
Can anyone give me or point me to an overview of the process for an older home like this?
All the information I have found talks about replacing windows with steel frames in the concrete but nothing about replacing older wooden windows and how to make it a nice solid fit. I do not want to have to order custom sized windows for every replacement needed but of course need them to fit solid.

Thanks.
Trent

Steel? No way. I would use solid vinyl.
Only you can know if they have to be custom or not. Since custom sizes are so expensive, I think it would be worth choosing standard sizes and re-mortaring the foundation to the required rough opening. If you haven't done that before, it would be worth it to hire a stone and mortar contractor who really knows the trade, or you will have something that crumbles off in a few years.
Then it's just a matter of caulking around the window to fill in 1/8-1/4" gap at most.
The specs with the windows will tell you what fasteners to use for a rubble foundation, or contact them, or the lumberyard will know.

Chances are there are no standard size for that application. Are they double hung , slider or just a sash in a frame? Post a picture and lets see what you have.