Yes, glass size is important. I think I'm going to remove the old windows and try to use the existing buck, if it's sound and solid. (but, keep some treated 2x4 on hand in case I have to build a new buck)
2 more questions:
-New construction windows (with the nailing fin/flange) if I screw through the flange into the buck, is that enough to hold the windows? Or do I still need to shim and screw through the shims?
-How do I weatherproof the whole thing? Liquid flashing on the existing buck? or cut/rolled flashing? I've seen people use tar paper, etc. is this needed?
Check the exterior dimensions and the interior dimensions. My guess is that the interior is smaller because the windows are mounted to the exterior brick veneer and back up to the interior stone/concrete. If that's the case you can just caulk that lip at the stone/concrete, slide a window into the brick opening (Which should be square.), attach it with Tapcons, and caulk the exterior joint. If the interior dimensions are significantly smaller it's a slam dunk. If it's only marginally smaller you're going to have to tear out at least one window to determine construction.
In any case if you frame/buck the opening I'd suggest all the wood be replaced. Those windows are very old and I suspect the wood is seriously degraded.
What I did was determine the minimum rough opening height and width and order the window to fit with 3/8" gap all the way around. This allowed me to shim the window squarely in the concrete RO & secure with tapcons into the concrete. I then sealed the gap with the minimal expanding foam.
For my small basement window I used PVC quarter round to trim out the exterior, mounted and sealed with an adhesive silicone based caulk. I have 24" overhang eaves so my windows do not see much rain unless it is blowing sideways.
Thanks for all the advice. I think I will be building a buck out of 2x6 treated lumber. I will probably use Tapcon blue screws, but was wondering- is there any type of brick anchor that doesn't require pre-drilling? This might simplify the installation. Thanks for any help, again.
Brick is probably soft enough that you could use a powder charged nail gun like a Ramset, but I think it might shatter the brick. Also, I've never tried it so you would have to check to be sure it would work before pulling the trigger. I think a hammer drill and Tapcons are the best way to go in your situation.
Yep, I think tapcons and hammer drill would be best too. Thanks all for the help!
For a basement window, in my opinion, I would go with vinyl or aluminum with spray foam insulation.