Monday, April 25, 2011

DIY: How to replace a window in a brick opening

Just in case you want to try tackling some replacement windows in brick openings yourself here's what we did in 18 or so simple steps. Actually, not so simple, but with the right tools it's not too bad. I'd rate it an intermediate DIY level - at least it is when you have brick openings rather than wood framed openings. We measured our rough opening from the outside which made it quite a bit harder to replace the window. The reason is that the inside of the brick rough opening is a few inches shorter than the outside. So we had to rip everything out, chip out enough of the brick and block in the way to make space for the new frame that fits the replacement window. There's not a ton of good information on the web about replacing windows in brick openings. Everything I found wasn't very detailed so hopefully this will help somebody else out. In the end using the larger rough opening allowed us to get a slightly larger window and a nice 4.5" window jamb that will better match the new windows we're installing in the addition. We're trimming all the windows out in a picture frame design so there's no window sill. We didn't save anything we ripped out other than the windows themselves so we weren't too gentle on removing all the pieces.

Time: It takes us about 4 hours from start to finish to replace one window as we tend to only work on 1 or 2 at a time (tool setup and cleanup account for a decent amount of time).

Tools: basic hand tools, demo bar, reciprocating saw, hammer drill, compound miter saw, angle grinder, and air nailer

Start with one old window

Tear off all the trim

Once you remove the trim casing there will be a little strip of wood attached to the window. Remove this and the bottom window slides forward.

Our top windows were held in place by this aluminum strip. Pull this off and the top window can be removed.

Pull out top window. We had storm windows so those were able to be removed next.

We did save the aluminum from the storm windows so we can recycle it, but they were only attached by a few screws.

Sawzall the old frame and pry it out.

Close up of what we were left with after demo.

The inside brick and blocks sticks out a little further so that needs to be cut down.

We measured and marked 4 inches from the interior wall and used an angle grinder to cut the line cleanly. Then followed up with a chisel to break up the rest.

New window in place. We built a new frame out of 1x4 material, attached that to the brick using tapcon screws (that's where the hammer drill comes in handy), and then set the window in place. Our windows have 4 screws at each corner that simply attach to the new wood frame once you have it level and plumb.

Trim the outside and then caulk it to make sure it's all water tight. We used 1x2 and 1x3 to trim this out. The brick sill was shaved down to make it ready for picture frame PVC trim.

Outside is already water/air tight, but I like to add spray foam all around the window to better seal it up.

We built the new jambs out of 1/2 inch plywood.

Slide it in and tack it up ensuring it's level and plumb and more importantly the reveals around the window match side to side and top to bottom.

I add a little more spray foam in the top and bottom once the jamb is attached.

Cut and tack up the new trim casing.

Putty the nail holes and caulk. Once you paint, you're done!


  1. when you order a new window, do you give them the measurements from the inside of the brick or after you install the 1x4's then take the inside measurements for order the correct size window?

  2. When you tear out the old window you could reuse the old rough opening and use those measurement. Our designer took the wrong measurements and our windows ended up being slightly big for the old rough opening. So we build new openings with 1x4's and were able to fit the windows. If you tear everything out like we did then I would build the 1x4 rough opening and use those measurements to make sure they size the windows 1/2" less than your opening. If you paid a company to do it they would just pop out the old and pop in the new windows. The only problem with that is you get a slightly smaller window than you had before. The way we did it was a lot more work, but the end result looks better with the largest possible window for the brick opening.

  3. Right now it is an old glass block window that is flush with the outside and on the inside I probably have a foot of window sill. THe old frame that is still there looks original from 1907 when the place was built. My idea is to take everything out, and reframe it with 1x4's up against the brick. Should I flush the window to the outside brick again or bring it in a few inches? Once I frame it in, i'll give them that measurement and i think they said the window comes 1/2" on the sides and a 1/4" on the top smaller to fit. Or something like that.

  4. Yea, that's what I would do too. Our walls were about 12" thick so I pushed the windows forward as much as I could and still allow for outside trim. None of our openings were 100% plumb/level so we had to fudge them a bit to make it look as level as possible. We made the insides more even than the outsides.

    Then on the inside we created a custom jamb to finish it out. If you do the demo before the ordering the window I would just have them include the jamb. You could even get new construction windows and probably cut away the flange enough to fit in your opening if they don't offer jambs with replacement windows. If you left a little flange you could use that to attach the window to your 1x4. Then foam and it would be solid.

  5. My plan was to not do the demo first just because I dont want a opening in my wall for the week or two it takes to get the window in. Also, it's a basement level and the window only sits about a foot about the ground so I dont want any mice/rats getting in. Thanks for the help but 1 more question. If i do a new construction window do I still need to fram it out with 1x4's or can I just slide the window right into the brick opening?

  6. Oh I see. I don't think a new construction window will work for that since it's a smaller opening. For my basement windows I just used an off the shelf from Home Depot. I definitely sacrificed some window size, but it was an easy install. Just take the rough opening on the inside or outside and subtract 1.5" or so to find a new window that will work. For mine I just got as close as I could, but I definitely could have fit another inch or two if I wanted to special order a window.

  7. Hi Brian,
    We have old 1976 windows on a brick house. We'd like to install the new window by attaching the flange to the outside brick, and then placing trim over the flange to hide it. In that way the window sill on the inside of the house is much deeper. It looks like your's is pushed out pretty far also. Is that what you did? Do you think our idea would work?

  8. Hi Selma,
    I would not use a new construction window with a flange for this. It will require a ton of caulk to get the trim and flange waterproof and most likely will fail over time and allow water in. We built out the frame to the back edge of the first layer of brick so we have about 5 inches to the front of the brick on the outside of our windows. Inside we have about 6-8 inches that we had to build a return for. Our walls our 1950's construction so we have a layer of brick and then two layers of concrete block before we get to the interior walls. I'm not sure how they did it in the 70's. The brick openings most likely aren't going to be perfectly square and will definitely not be flat so a flange would stick out too far I'd think to make it work. Get a replacement window without the flange and either build a new box or simply get a replacement window that fits in the current opening. That's what most window replacement companies will do to minimize the work. You end up with a slightly smaller window, but it will only take 20-30 minutes per window to replace.

  9. Hi Brian,
    OK, so maybe we'll use a replacement window, build a frame out of pvc and attach it to the brick. Then install the replacement window to the PVC, so that it can be pushed towards the outside further than a standard installation. That would give us a larger trim (I like craftsman styled houses) and a larger sill on the inside of our house.
    Thanks, this is the only place I have found where the window sits further out on a brick veneered home. I like it...

  10. Yea, I think that's a good idea. You could build a frame out of pressure treated wood too. You'll just need a little something to screw the replacement window in from the side - usually only 4 screws each window. Don't worry too much if it's not 100% secured as once you add spray foam and trim the window will be sealed up and solid. The way we did was definitely the hardest way. Any window replacement company would have just thrown in a smaller window and used the original framing to screw it into, but our way looks better in our opinion. The easy way would reuse the existing molding inside and out so the whole window would be done after some foam and caulk - probably only 30 minutes per window. Our way required about 3-4 hours each window.

    For the trim we opted to just picture frame all of the windows inside and out. We still have about 5 inches of a return on the inside as our sill. We preferred that look rather than a traditional sill plus I found it easier to install.