Vinyl Window Sill Bowed Up

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Texwindow
Posts: 27
Joined: Sun Jun 27, 2010 2:53 pm

Vinyl Window Sill Bowed Up

#1 Post by Texwindow »

I am in the process of installing a 48in x 80in single hung Jeld Wen Premium (3 1/4" frame thickness) single hung window and the sill is bowed up about 1/4". The bow in the seal is present with the lower sash closed or open. When installed the window sits directly on the floor, which is concrete. I was thinking the bow would pull out when I screwed the jambs to the rough-in jamb, but it did not. I am thinking of screwing the sill to the floor and using some silicone to water proof the screw penitration. According to Jeld Wen paper work for windows or sliding glass doors, you should not have to put any screws in the sill. The concrete in the rough opening is level. Anyone run into this before? Any suggestions? Please advise.

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Delaware Mike
Posts: 947
Joined: Mon Jan 30, 2006 1:32 pm
Location: Delaware, New Jersey, Philadephia Area

Re: Vinyl Window Sill Bowed Up

#2 Post by Delaware Mike »

Very wide vinyl double hung units can have a slight frown or bow to the sill in the center especially if they don't have a hospital or water dam integrated into the design of the window. We I've run into this I try to set the window's corners up onto shims and then determine where I would have to run a stainless screw through the sill at, should be dead center if one screw will work. With a fresh 3/8" forstner bit I will drill through the sill in just the first wall making sure to drill a clean precise hole with no burrs or boogers. I then would take my stainless anchor and get silicone on the threads and and shaft and start to go through the sill into the wood sill. I would hand tighten the anchor until the sill is level and not bowed. Then we take a factory supplied screw hole cover (vinyl like the nice one's Sunrise supplies in their screw packs) and put some more white or clear silicone on the bottom side of it. Press it in letting some sealant press out of the edges. Clean the excess sealant with some solvent and you should be good.

Of course in you case you may have to you Tapcons and some pre-drilling. I hate drilling through the sill but it's the lesser of 2 evils. You don't want a severely bowed sill that inhibits proper locking of the sashes. This is the method that Sunrise Windows teaches mechanics at their install program on a super wide double hung.

Texwindow
Posts: 27
Joined: Sun Jun 27, 2010 2:53 pm

Re: Vinyl Window Sill Bowed Up

#3 Post by Texwindow »

Thank you Mr. Delaware Mike sound like good advise, especially the part about installing the screw by hand with screw driver. Those screw drill/drivers can get addictive, but nothing gives you better feed back than a good old manual screw driver. Thanks again

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