When we left off last week, we had removed the old wood sash windows and prepared the opening for the vinyl replacement windows. Now it's time to install your new windows. You should have someone there to help you when doing the installation. First, Remove all shipping materials from the window. Now, if you are installing several different sizes, make sure you are putting the correct window in the correct opening. You need to put the window into the opening to make sure it's going to fit, then remove it and run a bead of caulk on the face of the outside blind stop where the window will rest. You don't want to caulk, only to discover the windows are too big or too small. It's worth the extra few minutes to make sure it's going to fit. Lift the window and set the bottom in first. Then raise the top until it rests against the outside blind stops. Sometimes, when raising the top into position, the window frame will hit the top of the wood frame. You need to tap down on the top of the vinyl frame while keeping pressure towards the outside.
Once you determine that it's going to fit, remove the new window and set it aside. Run a bead of caulk on the face of the outside blind stops. White latex painters caulk works fine. Raise the window into position again. Now have your helper hold the window in position while you raise and lower the sashes, making certain that the window is square in the opening. Remember how you ordered the windows 3/16"- 1/4" shorter than the tightest measurement? This is where you use this space to adjust the frame to be the most plumb and level. Get a box of popsicle sticks and wood coffee stirrers at the grocery store. The coffee stirrers are about 1/16" thick, and the popsicle sticks are approximately twice as thick. You want to put the shims in the four corners and when you have the window plumb and level, put one screw into the top center and bottom center of the window to hold it in place. Then caulk the gap on both sides and along the top before installing the inside stops. I don't recommend putting any screws in the sides of the window frame as they can interfere with the mechanisms that raise and lower the sashes. Remember, we still need to re-install the inside stops.
Before installing the inside stops, remove all the old nails and replace them with new nails. A 1"- 1 1/4" finish nail is fine. Before installing the inside stops, scrape all old caulk off the stops. Then nail your stops back on. If the window has 4 stops, install the shortest ones first. That way you can bend the longer stops into place between the two short ones. Use a nail punch to sink the head past the surface of the stop. If you have several windows to do, I suggest doing the first window to this point before going to the next. How frustrating would it be to have a helper removing the old sashes, only to discover that the windows aren't going to fit!? If the first one goes in fine, then you can send your helper ahead of you to start removing old sashes. The best way to avoid the nightmare of having a bunch of new windows that won't fit is to make sure you measure CORRECTLY. Remember, tight minus 1/4" on the width and 3/16" on the height should be fine. Finish the inside by caulking the area of the inside stop where it meets the casing, and the point where the stop meets the new frame. Fill the nail holes in the inside stops with caulk to hide the nail heads.Now it's time to finish the outside. A quality replacement window will either have a sloped frame to match the slope sill, or it will come with an insert that fits under the new frame to fill the gap created by the sloping wood sill. If you buy a lower grade window that doesn't come with anything to fill the gap underneath, you can buy some wood trim to fill the space, or you can get a flat vinyl trim that attaches to the face of the bottom of the new frame. The flat trim is available on my website under the "shop" tab. Once you cover the bottom gap, it's time to caulk where the outside blind stops meet the vinyl frame, and where the bottom gap filler meets the wood sill.