How to Install Vinyl Windows

Most houses have to retrofit windows because the measurements of the old windows are odd sizes. Home Depot, Lowes and other major hardware stores won't carry the odd sizes so you will have to retrofit (special order) the new window. In this case, my friends, the Chases, have new construction size windows. Meaning the windows are 4x4, 3x3, 5x5, etc (even though it is not a newly built home). This means that Home Depot and Lowes will carry these size windows and there is no special ordering involved. However, these windows come with a plastic flange that plaster or siding will attach to. I will be cutting off this plastic flange so we don't have to damage the existing plaster and re-lathe and plaster around the new window. This way will save time and money. I will be adding backer rod and caulking to it. I'll show you. Let's make it happen!


Your standard 4x4 wood window. We want to update the house by putting in a new standard 4x4 vinyl window.

First we want to measure the existing RO (rough opening) to make sure that the window that we purchased will fit in there BEFORE we take apart the old window.

Now that we know that the new window will fit we want to take out the old window without breaking it and the way we do that is by prying all the existing molding from the inside jams. Those are what are holding the window in.

From the inside of the house you want to take out all the casing (molding) from around the window. Without this molding the window should come right out.

Most old sliding wood windows will have a wire or some kind of spring on the sides of the window so that the window won't slam shut. When taking out the window you'll have to remove this wire or spring. In this case it's a spring and we're cutting it off with snips.

Now that we have our inside pane removed we move to the outside. Pop the exterior moldings off and....

it should slide right out! Again we'll have to snip out the spring. On this particular window both panes were able to slide so both panes had a spring (or in some cases a wire)

Break time! Just kidding. Now that we have our old, outdated window taken out and the inside jams are all smooth (no nails) we're ready to install the new window. First let me show you what I was talking about with that flange.

This flange is used to attach to the king studs (the 2x4s on the sides), the head (the 4x4 on the top) and the sill (the 2x4 on the bottom). We will not be using these flanges to attach the window to our framing because we do not want to mess up our existing plaster. If we were to use these flanges we would have to take 6 inches of plaster out all the way around the window and then screw the flanges to the existing framing (king studs, head and sill). I would not recommend cutting the flange off unless you have a 3/4 inch slope windowsill. With the 3/4 inch slope windowsill water will never enter the window because water travels downhill and not uphill.

You want to pre-drill a hole in the bottom, top and sides of the window so that once you have the window up it's easier to screw it in.

Center your window. In this case we have a 48 inch RO (rough opening) and a 47 1/2 inch window. So, by centering the window you will have a 1/4 inch gap on each side of the window. Set a 1/4 inch shim on each side of the bottom of the window and screw both ends of the bottom. Make sure you are flush with the interior of the drywall so the molding can go right around it.

Level up the side and...

screw the top. Again, make sure the top is flush with the interior drywall. The exterior side doesn't really matter right now because you are going to cover it with molding anyway. Do the same to both sides of the window.

Now with the window installed add backer rod (a foam round backing) Backer rod is so that you don't waste a lot of caulking. You want to push your backer rod about 1/4 inch into the gap between the window and the framing. Install the backer rod all the way around the window. **Side note: Another option is to use spray foam but to me it's messy (it'll get all over your new window), it costs more and backer rod is just plain easier to work with. **

With your backer rod installed go ahead and caulk around the window applying the caulk against the backer rod (1/4 inch deep). Most caulking says it won't shrink but just in case check it in the morning and make sure there are no shrink spots. Shrink spots are gaps or holes where water can get through and cause water damage. After your caulking go ahead and apply your finish molding to the inside and outside of your window.

And...you're done! Once again...we made it happen! Stay tuned to see how me and Mr. Michael Chase apply the molding.

P.S. Thanks to my friend, Heather, for taking some great pictures and helping me with this project!