Installing a window in a freshly framed opening is one of the more simple tasks in a construction project.
Most new construction windows have what is called a nailing fin. These are found on vinyl or aluminum clad windows. This nailing fin is either vinyl or metal and has nail holes every 4 to 6 inches and about 1 and 1/2 inches wide. Nailing fins take the place of brick molding which can still be found on primed wooden windows.
Not only do these fins make installation easier, but also make a better seal against water and air infiltration. These windows can be flashed if desired but not deemed necessary. A window that does not have the benefit of a soft fit or porch roof above it may need flashing or a drip edge above it.
When getting ready to install a window, make sure the sheathing is not hanging into the rough opening. This could cut down the size of the opening and not let the window go into the opening. Once this is done, measure the rough opening to make sure the it is big enough for the window. You don’t want to lift a heavy window to an opening only to find it won’t fit. Rough openings are usually 1″ wider and 1/2″ taller than the window unit. Rough openings are spec and provided by the window manufacturer.
Depending on the size of the window, you’ll need 2 or 3 people to install a window. One or two outside and one inside.
Once you know the window fits, lift it to the opening from the outside. Set it on the sill and push it into the opening until the nail fins hit the wall. Make sure none of the fins folded themselves back into the opening especially the bottom one. The person on the inside then centers the window in the opening. Then using a level, checks it for plumb and level, and applies shims where needed. You may also want to check the window for square, although a window that’s closed and in the locked position usually is. The window can now be nailed in. My preference is roofing nails but 8d nails or cap nails will do the job.
If it is a standard jamb (4 9/16) another thing to check is how far it runs past the rough framing. This should be 1/2 inch. You’ll also want to make sure the window operates properly. Double hungs should slide up and down easily and casements should crank in and out without hanging up.