Bridging the gap between existing drywall and new glass block windows
November 2, 2014 12:46 PM   Subscribe

Some friends recently had their deeply recessed basement windows replaced with glass block. So far, so good. The problem is that there is now a 3-5 inch gap between the end of the drywall of the recess and the glassblock, giving a not-so-lovely cross-sectional view of their exterior wall. (If I'm not explaining it well, here are pictures.) The question is: what is the best, least time-intensive way to bridge this gap?

Part of the difficulty in researching this is that I'm not sure what the relevant terms are, but so far the ideas that have been floated include:

1. Just put in drywall.

Problem: There's nothing to attach the drywall to: no studs on any side, a ~2" drop-off on the bottom before hitting cement, and uneven masonry on the left, right, and top sides.

2. Just tear out the whole recess and redo it.

Problem: It seems like the most-correct approach, but it's way too time-intensive.

3. Building a wooden frame in place and then attach dry wall to that.

Problem: There isn't room to do it without introducing a weird "step" between the outer part of the recess and the new part closer to the glass.

4. Finish off the corners of the existing drywall, fill the bottom and left & right gaps with cement and bridge the top gap using some flexible aluminum flashing. Then paint the whole thing to more-or-less match the painted drywall.

Problem: Would need some kind of mold to make an even vertical slab of cement on the left and right sides, but so far this is the winner.
posted by jedicus to Home & Garden (7 answers total)
Is this purely a visual issue, or is there an insulation issue? If it just looks ugly, I'd spackle, sand, and paint.

However... shouldn't whoever did this work be dealing with this out of their own pockets? The job doesn't look finished.
posted by showbiz_liz at 12:52 PM on November 2, 2014

Response by poster: Purely visual. The windows themselves are properly installed (as far as I know), and there's no significant draft coming in through the exposed masonry. Evidently the job was just for window installation. Prettying things up afterward was not part of the deal, but the friends are kind of at a loss as to how to proceed. They had assumed the solution would be more readily apparent.
posted by jedicus at 1:04 PM on November 2, 2014

This may be a bit vague, since I didn't actually SEE how he did it,but my brother did a very similar project in his basement. He finished off the extra space with what looked like some sort of cement that was trowelled in a nice smooth arc all the way around the window. It's painted to match the rest of the room. It looks great, but then my brother has some seriously handy home skills.
posted by LaBellaStella at 1:41 PM on November 2, 2014 [1 favorite]

Nah. If you have a chop saw, Just buy some very big cove moulding from your local big box store. I'd put it in with some Liquid Nails.

The shape of the cove moulding will cover the gutter, and it will be a pretty frame. Stain it, or paint it white as a window frame.
posted by Ruthless Bunny at 2:14 PM on November 2, 2014 [1 favorite]

Don't really have a solution but here's 2 thoughts: what are the glass bricks sitting on??? freaking me out! and on a more practical level, if it's an outside wall make sure it's weather proof. Water getting into the wall cavity can only be bad news.
posted by Julanna at 3:30 PM on November 2, 2014

Response by poster: Just buy some very big cove moulding from your local big box store

That idea was also floated, actually, and the concern was that it would be too expensive (or difficult to find at all, in the case of cove moulding in the 3-5 inch range).

what are the glass bricks sitting on???

They are set into (and sealed in) the exterior wall. Since they were installed by a professional the friends are pretty confident about the weathertightness of the windows themselves.
posted by jedicus at 5:35 PM on November 2, 2014

Dressing it up is easy if a bit treehouse. Some 1x6 clear pine with a few shims, some paint and some hot mud will do that. This is also wrong.

The problem is condensation. Glass blocks have an R value [insulation] of 1.96 which means you don't want to have wood near the glass blocks because of condensation.

Looking at the pictures I would leave the bottom sill, wire brush the fuck out of it, and repaint the flashing. They make a lot of great products for that, you don't want to finish that any more because moisture will get in there and fuck up the program.

Wire brush the bricks so they look cool and span the gaps between the bricks and drywall with rabbeted moulding.

The top part, above the window, needs [re]painted, preferrably with Killz and trimmed out with some one by clear pine.

It's doable for maybe fifty dollars.
posted by vapidave at 7:47 PM on November 2, 2014 [2 favorites]

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