Extension jamb over fiberglass

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phryder
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Joined: Thu Jul 12, 2012 12:56 pm
Location: Kansas City, MO

Extension jamb over fiberglass

#1 Post by phryder » Fri Aug 30, 2013 12:37 pm

Hello,
I am installing a Marvin Integrity all Ultrex fiberglass awning window in a bathroom. I am wondering what is the best way to attach an extension jamb, about 1-1/2 inches, to the fiberglass. Screws, nails, adhesive or ...? Another possible issue is that my intent is to use pvc for the extension and am wondering if any thermal coefficient issues might arise. Any suggestions will be greatly appreciated.

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HomeSealed
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Re: Extension jamb over fiberglass

#2 Post by HomeSealed » Fri Aug 30, 2013 1:09 pm

Despite what the fiberglass salesman may have said, no, no expansion coefficient issues will arise. The difference is negligible to non-existent over the length of material associated with a residential window application.
To fasten the extensions, your main "support" should be shims built up behind the lineals. Shoot through the shims, then you'll add strength when you tie it in with the casing. Adhesive would be fine between the JE and the window, but I would NOT shoot fasteners into the window frame. Alternatively, you could build the whole thing (JE and casing) on the ground and then attach in one piece, but it really needs to be put together well to do so.

phryder
Posts: 7
Joined: Thu Jul 12, 2012 12:56 pm
Location: Kansas City, MO

Re: Extension jamb over fiberglass

#3 Post by phryder » Fri Aug 30, 2013 1:35 pm

Alternatively, you could build the whole thing (JE and casing) on the ground...
That's exactly what I was thinking. Build the je and casing out of pvc, glue and screw it together to make one monolithic piece and use silicone caulk between je and jamb. The window is over the tub with the top of the tile about half way up the window. It's a small window, with an od of about 30" wide x 20" high. The tile is set in mortar. Normally, if this was new construction, I would wrap the tile around the opening to the jamb but I don't want to make that big of a deal out of this project.

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HomeSealed
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Re: Extension jamb over fiberglass

#4 Post by HomeSealed » Fri Aug 30, 2013 2:41 pm

That will work :D

Window4U (IL)
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Re: Extension jamb over fiberglass

#5 Post by Window4U (IL) » Sat Aug 31, 2013 8:47 am

I always nail or screw my extension jambs together before installing them. It's much easier to get them lined up with the proper reveals that way, and it just makes for a more solid installation. I also nail my casing together at the corners with brads and put it up like a finished picture frame for the same reasons. I couldn't imagine nailing it on a piece at a time after doing it this way for so long.

phryder
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Joined: Thu Jul 12, 2012 12:56 pm
Location: Kansas City, MO

Re: Extension jamb over fiberglass

#6 Post by phryder » Sat Aug 31, 2013 11:59 am

I always nail or screw my extension jambs together before installing them.
I hate to admit it but I never thought of that until now. Usually, I am working on wood windows, at least on the inside half, and the thickness of the je is considerably less than the 1+" that this job will take, and I attach the je to the jamb with glue and brads, followed with with the picture framed casing. Lately, I have become more comfortable with pvc trim, screws, and solvent. It's easy to work with and costs less then wood. I don't foresee any problems making a pvc je/casing assembly. With the aid of the solvent, I think it will be plenty sturdy, and I won't have to worry about any consequences of penetrating that expensive piece of fiberglass

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