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Replacement windows in concrete block construction

Replacement windows in concrete block construction

Old 12-30-10, 07:31 AM
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Replacement windows in concrete block construction

I am planning out a project to replace windows in a concrete block constructed house. I have replaced windows in a house constructed with wood, but never in concrete. I do not plan to change the size to avoid any cutting; however, I seem to be clueless as to how to buy replacement windows. I proved this talking to the guys at the big box store. I took several measurements of the existing windows to price out the cost, but they could not help me. I have the following questions:

1) I plan on buying the replacement windows before removing the old ones, is that crazy? Do I risk not ordering the right size? Any tips on measuring would be appreciated.

2) Assuming the right size is delivered, I believe I will be able to remove all of the old window and replace with the new window in the same opening. I know I will have to trim it up, replace drywall, stucco, and spray foam any gaps. Is this too simple of an assumption?

3) Once I am into the project I will figure out how to screw the window to the block, but I figure I can use tapcons or connect wood to the block and screw the windows into the wood.

Thank you for the time to review my question.
Old 12-30-10, 08:31 AM
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Yes, measuring is the most critical part of the process, since if you measure wrong then you are stuck.

You can install a window in a masonry opening at least 3 different ways. Either you can order it about 1/4" smaller than the masonry opening and shim/screw it in place then caulk the edges- this is the easiest, best way IMO- (provided it is straight on all 4 sides and the opening is perfectly square) or you can anchor some stops onto the masonry and push the window against the stops, shim/screw it in place, and caulk it to the stops. Some guys will install a 1 1/2" woodbuck to the masonry opening so that they can install a window that has a nailing flange. But on small windows that isn't too practical, because you lose a lot of window area.

In both instances, the masonry sill would need to be sloped to provide drainage. If it isn't, you need to mortar up a slope onto the sill.

Replacement windows are usually about 3 1/4" wide, so you can kind of get an idea about how wide the window will be, compared to the existing window. You can install it wherever you want in the wall as far as depth is concerned. If the old window was thin, the new window may stick into the house farther than before. I usually prefer to keep the exterior of the window in the same spot as it used to be.

So in answer to your questions, 1). yes you can figure out what size it needs to be- you may need to remove some drywall on the inside to make sure. Measure inside and out so that there are no surprises. 2). That is pretty much it. But you will be wise to use a urethane sealant on the exterior, such as OSI Quad or Vulkem. If you foam be sure you don't overdo it, and be sure you use window and door foam so that it doesn't over-expand. Foam the window first, let it dry, cut off any excess, then caulk. You don't want foam oozing out of a fresh caulk job. If you can, caulk the inside perimeter too just to air seal the frame. If there is drywall on the inside it is sometimes better to just remove the drywall inside the jamb, and install new drywall up against the new window. Or forget the drywall and trim it with wood. 3). Use wood shims to shim the window in place at the corners. If you install shims in the middle of the window be sure you are not bowing the frame in. Tapcons will work well, I prefer the 1/4" hex heads. As to the length of screw you need, they will need to screw into a minimum of 1" of cement, so a 2 1/4" screw might be what you need. Maybe have several sizes just in case. Do not overtighten them or they will strip.

If you want to take a picture and post it, then we can see what your window opening looks like from the outside, which might help us give you better advice.

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