Do you have a picture or drawing? I'm having a really hard time envisioning that.
Is the glass block currently set in the masonry, or in the rough framing?

Masonry house (two wythes of weight bearing brick) or brick veneer (one layer of brick over a wood frame house?

I'm in the process of demo'ing the bathroom (floor to ceiling tile set in mud and metal lath).

I'll get some pictures of the window soon.

I want to decrease the height of the current window (from the bottom), and replace it with a strip of glass block ( the magenta rectangles) and a casement window. The red is the framing I'm going to add.

The casement is going to be set into the opening, I can get an Anderson 400, built to the exact size of the rough opening, so this is no problem.

The green is the window sill that I'm having problems figuring out how do it.

Internally, the glass block and the window have to rest on something and I figure it needs to be waterproofed?

The sill needs to slant downward.

How do I tie all these elements together?

Modern windows are not really designed for masonry openings.

You often end up having to instal some wood framing to anchor the window.

I would dread the idea of using Tapcons into masonry on a modern window.

+1

A buck frame is usually required to get a really good attachment point.

I have a solid masonry house and am considering replacing the old rope/weight wood windows. Inserts seem to loose way too much glass and change the ratios that make the house look original. But isn't this also a problem when using a buckframe for full frame tear outs? What exactly is the problem with just using masonry clips and anchors directly to the masonry. I agree that Tapcon screws into porous block to secure the masonry clips would be problematic. But there are other anchors specific for concrete block- sleeve anchors or the screws using the plastic or lead surrounds.

Brickeye, I noticed comments on this forum from you from 2007 basically saying that buckframes in solid masonry for new full frame windows just serve to lose glass and increase installation costs and hassle. It almost seems like a boondogle for installers considering all the flashing and molding that buckframes require. Have you changed your mind?

Well here's what I ended up doing:

I ripped off the brick mold - and found out that the window opening was framed - and had about 3/4" reveal.

I measured this rough in opening, and ordered a custom size Anderson window, with no nailing flange. It came predrilled with installation screws.

I removed the old window, and temporarily attaced 1X4's across the outside window opening (on the 3/4" frame) - this prevented the window from falling out. It was just a matter of pushing the window into the frame and shimming. You're going to have to add extension jams.

Took me about 2 hrs to install. I used some composite brickmold, screwed into the frame, and caulked. The composite stuff is expensive - but you don't have to paint - if you like white.

If I were you I'd gently pry off a piece of brickmold and see how your windows are framed.

There is no casing on my windows, brickmold or otherwise. The frame is set into the masonry opening with some sort of messy caulking around (its clearly been calked over several times). That is how I would like to have it done with a replacement window - no casing, no buckframe - just the windowframe right up to the bricks and sealed with a sealant. I am not sure how the frame is presently attached to the masonry.