Is a wooden buck necessary when installing windows into full width brick?

Question

I'm looking for pointers on installing a new window into a full width brick wall. Pictures are here. They are the basements windows in a rowhome. There's a slanted brick sill on the bottom. The brick is covered with formstone on the outside. At the top there's a wooden shelf on the backside and arched brick on the front.

Specific questions:

1. I'm considering installing directly into the masonry without the buck frame. In that case, do I have to use a separate sill? The house already has a slanted brick sill; should that suffice? Also, it has formstone that wraps around the masonry on the sides and top, do you think it's necessary to add framing or something so that the lip of the formstone doesn't trap water? I think it would be minimal if it did.
2. If I do add buck, can I just do it on the sides and top? If I add it on the bottom, should it be slanted like the sill underneath?
3. I'm also planning to install iron bars later. Should I make the buck framing go from formstone to the inside brick edge (about 7") or is 5/4*6" PT pushed up to the formstone okay? In which case, I guess I would line the window up on the inside of the buck to leave space on the outside for the iron bars and I could install extension jambs later if needed?

Answer 1

Windows are installed directly to structural masonry openings in Europe all the time. Since you already have a sloping sill, you're good there. You'll need to have the windows fabricated for a very small gap between the windows and the brick. Then screw the windows into the brick with shims and masonry screws, and fill the gap with backer rod and caulk on the outside (100% silicone, butyl, or polyurethane--no latex/acrylic!) Spray foam the remainder of the gap from the inside, and finish the interior however is most appropriate--likely with plaster.

Don't worry about your formstone cladding. It won't hurt anything, especially if the brick sill extends beyond the formstone, allowing water to fall down through the air rather than dribbling down the side.