Replacement windows in block wall?

If those old windows were done properly they are setting in a slot in the blocks on each side and then mortared in. When you cut the mortar if you can- you will find the Window frame still locked in to the block by the slot.

This is a big job for little gain- you must also consider that adding wood to the side will reduce the opening and no standard size window will fit, that means a special order window- higher cost

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Two years ago I was the foreman for a construction company. We were contracted to replace old aluminum slider windows with new vinyl windows that retrofit into the existing openings. The caveat was that we were replacing thousands (no exaggeration) of windows in a variety of apartment complexes. All of the openings were carefully measured and new vinyl windows were custom manufactured. Contact Milgard windows (who we used) or another manufacturer and inquire about your project's specifications. They can also assist you with installation techniques as well. As for insulation, we used 'Great Stuff' and foam weather seal that was caulked with a silicone bead. All of our projects were on stucco veneered apartments though an installation on brick or siding buildings would not be much different. In a few cases it was necessary to enlarge slightly the opening and in some we had to shrink and repair the opening due to previous structural problems. If you are a reasonably skilled carpenter you should have little difficulty accomplishing such repairs prior to installation of new windows. I can say that the sound insulation properties were phenomenal. Double-paned glass will make quite a difference in sound as well as temperature abatement.

Depending on the replacement window construction, you may be able to attach the window directly into the block using tapcon screws (I assume this was what you were going to attach the wood to the block with anyway). The new windows must be able to be installed by attaching through the frame. It would have a flashing kit to cover the openings after installation. As usual, you would need to add insulation between the window frame and the block and caulk the open areas.

This sounds dangerous to me. You're risking leaks for both water and cold air. I'd go to Lowe's or Home Depot and talk to the "window folks". Then if thats not satisfactory call a custom design vinyl window manufacturer in your area. There's got to be one or two. Basement windows are usually of standard size so to try to do Mr. Fix it yourself stuff is a sort of wasted effort I feel. Good Luck Stew

I'm not an expert but it sounds like a good plan. I would make 2 more suggestions. 1. paint your pressure-treated wood on all sides and joints (all 6 of them!) to help seal it off from the moisture, using a water resistant primer and paint, BEFORE installing the wood. 2. securely attach the wood to the cinder block with long lag screws or other bolts to make it more secure from an intruder (you want to make it as hard as possible for someone to just kick in the window).

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No...it's a huge "pane" in the butt (sorry) but you're goin' about it the right way.

Option "B" is to tear up the masonry to get the window frame fins out.