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yamster 06-18-2011 02:13 AM

Replacing Windows... How Do I seal the Outside Gaps?
Hello everyone. First time posting.

When installing replacement windows (the ones without flanges around them), what should I do with the outside gaps? For inside gaps, I guess i will fill them up with some sort of expanding foam and then cover them with a frame, but what about outside? Will/shall the gaps be small enough that I can simply close them with some caulkings?

Thank you for your answers in advance!

Have a nice day.

Just Bill 06-18-2011 06:31 AM

If you have gaps, the windows are the wrong size. And NEVER use expanding foam on door or windows, it can cause the frames to bow, and possibly jam things from working.

Replacement windows should be about 1/4 smaller than the opening. With this dimension, there will be no gap on the outside, and a small gap around the perimeter that gets insulated with NON expanding foam such a DAP Foam. That gap is also small enough to be covered by the original stop molding.

yamster 06-18-2011 07:31 PM

Just Bill,

Thank you for your reply.

Obviously, I haven't replaced windows before... :)

Fortunately, it's not like I have already installed a window and wondering what I would have to do with the gap I see from outside... I was just assuming this 1/4-1/8" gap around the frame would also be visible from outside as well.

So, if that "wiggle room" gap is visible from inside but from outside... I guess that means the exterior wall must be covering the gap, overlapping the window casing a little bit. Is that the case?

Oh well, I can't help feeling that I am asking dumb questions... but then again, who will I ever learn if I don't ask? :)

Thank you for your reply and patience.

thomasjmarino 06-18-2011 08:29 PM

You need to follow Bill's direction and find yourself a competent sider to cap the exterior window frames with pvc aluminum.
A good sider knows how to bend the aluminum so that it slides between the window and window stop.
Then all you have to do (or the sider has to do) is run a nice clean bead of caulk (silicone).

Tom Struble 06-19-2011 07:28 AM

well actually i think the op is right,there should be an exterior stop

yamster 06-19-2011 07:37 AM

Hmmm... so... there's this cap or stop on the outside that covers the gap?

Well, then can we say the outside gaps are closed by this cap/stop, instead of there should be no gap outside (because of the cap/stop)? :)

Should I take some pictures of how the windows in my house look from outside?

kwikfishron 06-19-2011 07:45 AM

199 Attachment(s)

Originally Posted by yamster (Post 669875)

Should I take some pictures of how the windows in my house look from outside?

We like pictures.:yes:

yamster 06-19-2011 09:08 AM

I can't really see any stops or caps around the window from outside. When removing the existing window, everything inside the caulking line (white stuff) should go, right?

Here are some pictures. First time trying to post pictures... I hope it works.

Thank you!

kwikfishron 06-19-2011 09:34 AM

199 Attachment(s)

Originally Posted by yamster (Post 669924)
When removing the existing window, everything inside the caulking line (white stuff) should go, right?

Yaall the white stuff goes.

Your replacement (no fin) windows are the wrong choice for that application IMO.

yamster 06-19-2011 10:11 AM

I haven't bought any windows yet... So, when I do, is there certain type of replacement window (other than it being a casement window, which is the style of the existing one) that I should get, for the particular type of installation method used for my window?

kwikfishron 06-19-2011 11:10 AM

199 Attachment(s)
What you want is a new construction windows with the fin.

There are two ways to do the install. With one you end up with exterior window trim, the other will look just like you have now.

1) cut back the siding a couple if inches to access the nail flange to remove and then install the new window. Then hold your new trim against the window, scribe and cut the siding again. Install new trim.

2) Remove the siding around the window. Pull the old, install the new and re-install the siding.

With both options you may or may not have to mess with the interior trim. In most cases you do though.

That is a very quick overview. There are other critical details involved with both methods but it gives you the basic idea.

yamster 06-19-2011 01:35 PM


Thank you for your explanation.

So... this confirms my greatest fear. I've seen one YouTube video in which the installer had to remove the siding to install the window... It sounds like I would have to do the same with my windows.

This would be considered as one of the more difficult window replacement jobs, right? I've also seen some YouTube video from Home Depot, and they claimed replacing window is very easy thing to do - in their video it actually looked very easy; all they had to do was literally "dropping in" a new window into the opening. What I would have to do with my windows, I believe, is certainly a lot more work than that...

At first this new information made me think that I may have to hire pros (since it's more complicated than I initially thouhg), but on the second though, maybe this gives me more reason to do it myself; I would think pros will charge me more if there's moer work to do.

By the way, are the siding panels (I think they are cedar) usually reusable? I mean, if I don't butcher them when prying them out, will I be able to put them back up after installing the window? Or, will I need to install new boards and paint them?

I would like to thank everyone who took his/her time kindly answering my questions.

kwikfishron 06-19-2011 02:18 PM

199 Attachment(s)
There are installers that will cut your window out of there, drop in a no fin replacement window, attach through the frame with screws, caulk and be done with it. Its fast money.

The problem with that type of install is your relying on only caulking as your defense against the weather.

If you do decide to hire a contractor be sure you know what method of installation hell be using.

Removing and replacing your cedar lap without destroying it can be a challenge at best to impossible depending on how old and brittle the siding is. This is one area where experience could be key.

You dont have to remove the siding if you dont mind the look of trimmed windows.

yamster 06-19-2011 03:06 PM

So, I guess I can ask contractor prospects how they are going to install a new window and judge their workmanship by their answer. :) Great tip.

I don't mind look of trimmed window personally, but one fact I didn't mention in my previous postings is that I live in a townhome. I am quite positive the association won't allow me to have different looking windows from my next door units. :)

HomeSealed 06-20-2011 04:33 PM

An insert style window (goes inside your existing frame) can be installed and flashed effectively in that application (not just relying on caulk), however it is a "higher-level" task. Most guys would probably do it it the cheap way as ron warned against. Most times in situations where we are dealing with condo associations,etc, they have preferred the insert style as we can get the trim to mimic the original look and match more closely to the other units. The fact that you have no 1xX or brickmold around the exterior would pretty much necessitate the removal of all of the surrounding siding for a full tear-out, due to the fact that as you described, the HOA/Condo Assoc. probably won't accept fat trim around the opening. A full tear-out of that nature is also a pretty high-level installation. I really don't recommend DIY either way, or anytime where substantial flashing detail is necessary, but I guess this is the DIY forum, right? Just do alot of research, maybe find some good youtube videos or something.... Messing up twin casements would be a pricey mistake.

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