new construction window install: q. about shims and expansion

tom248October 31, 2011

I am in the process of installing new construction windows (Andersen 400 Tilt&Wash Double Hung), and have a question about the installation.

The installation instructions say to shim the sides at top, middle and bottom. Fine, I can do this. I believe this is to prevent bowing of the windows. But I wonder, what about expansion/contraction? How will expansion/contraction occur when the sides are shimed in three places? Won't the shim interfere with the normal expansion/contraction of the windows within the rough openning? The windows I am replacing are 30 year old wood windows and they were not shim'ed at all on the sides.

Sorry if this is a silly question. And I have no problem following the recommended install instructions. But I just can't get past the expansion issue when the shims are concerned.


Thank you for reporting this comment. Undo

I will start by saying expansion and contraction on the windows installed in a home is less of an issue than windows not properly shimmed to keep the jambs straight. I would make certain the units are properly shimmed per the manufacturer.

    Bookmark   October 31, 2011 at 4:13PM
Thank you for reporting this comment. Undo

Wood does not change length appreciably with moisture content.

It changes width and thickness in a typical piece.

The windows do not need any room top expand in the rough opening.

    Bookmark   October 31, 2011 at 7:22PM
Thank you for reporting this comment. Undo

Installed properly, you should not have any issues.

Proper shims and spray foam are your best tools in this application.

    Bookmark   October 31, 2011 at 9:21PM
Thank you for reporting this comment. Undo

thanks everyone for the replies and assurance i was not missing something. I guess the 1/2" extra dimensions in the rough openning to window size spec is to allow for the rough openning to be 'rough' and therefore not as precisely square as the window, as well as to allow for sealing (with insulation or foam, i'm intending to use mostly foam).

I guess after installing hardwood floors throughout my home over the past year, i've been so focused on the expansion gap necessary at the walls, that not having space for the expansion in the windows seemed strange. However, flooring of course has a lot more wood surface from which to expand.

thanks again.

    Bookmark   November 1, 2011 at 12:42PM
Sign Up to comment
More Discussions
Feedback / sanity check on Marvin & Kolbe quotes
So I got my rough quotes from a local Marvin Design...
Opinions on Sunrise vinyl sliders?
I bit the bullet and went with Okna windows! Not biting...
Decorating a new windowsill?
Hi everyone, We are a small growing business specialising...
LightGlow UK
Replacement and New Coastal Impact Windows
We are doing major renovation on a waterfront home...
Best garden window?
I am remodeling our galley kitchen. It's small and...
© 2015 Houzz Inc. Houzz® The new way to design your home™