I'm planning to replace the double-hung windows in my house, which are about 40 years old. They don't seem to match the examples I've seen, so I'm a bit unsure about my measurements. I want to do insert replacements, and I think the unpainted wood in the photo is the frame that will stay in place. However, the distributor wants the measurements based on the rough opening, assuming the windows will be a half-inch smaller. I feel that's incorrect since the gaps, shims, and frame exceed half an inch by a lot—there's a one-and-a-half-inch gap below the bottom frame in my second picture. I'm confident with tools and woodworking, but I'm anxious about making a mistake and ordering expensive, custom windows that won't fit!
1 Answer
First off, measure the rough opening height and width. Ensure everything is plumb, level, and square. That's crucial so you know how much smaller to order the windows. You also need to check if your rough opening will work with the home's exterior. Sometimes, if you've got brick or stone, the rough opening measurements won't be as useful. If you're unsure, consider gathering your measurements and having a professional review them before placing an order!

I have siding on the outside. How do I check if the rough opening will fit the exterior? Since I’m using inserts, shouldn’t they fit behind the exterior trim without any issue?