Retrofit Install: Is "Blocking" support normal?

For those self-installers
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Joined: Thu Feb 16, 2006 4:04 pm
Location: SF Bay Area

Retrofit Install: Is "Blocking" support normal?

#1 Post by kaydee » Thu Feb 16, 2006 4:41 pm

Hello Gurus,

I was reading the AAMA publication AAMA 2410-03 "Standard Practice for Installation of Windows", which I downloaded from Milgard site.

This is an interesting and useful document for retrofit installations.

It talks about "blocking" between the old frame and the new frame to ensure sufficient structural support. I would imagine this would be strips of wood placed into the channels. In particular, see the figures in the document at the bottom.

Is this "blocking" common practice in the industry? Do you professionals always use it?

I'm planning to do a DIY install and want to get educated.


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Joined: Sun Feb 12, 2006 3:21 pm


#2 Post by Tru_blue » Thu Mar 02, 2006 9:31 pm

The blocking you're referring to is the correct way to do it when installing windows into an existing aluminum frame. Otherwise the vinyl window frame would be potentially resting on a very narrow ridge of aluminum and could twist or sag. The blocking creates an even, flat, surface and provides support to the new window frame. It also fills in what would otherwise be a potential hollow spot under and around the window.

Is the blocking always done? It's supposed to be! But unfortunately there are always people out there who take shortcuts. Proper installation is SO IMPORTANT for a window to function and perform properly.

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