Shims

[newton homeowner]

Hi. I'm currently having windows replaced in my 104 year old Massachusetts home. We are using new construction Pella 250 series vinyl double hung windows with nail fins. So far, our contractor replaced about 10 windows and none of them have shims on the sides. The gaps on the sides of each window between the rough framing and the window frame vary between 1/8" to 1/2". Every window frame is slightly wider in the center than at the top and bottom. The difference varies between 1/16" to 1/8". Is this okay? The windows are fully nailed using the nail fins, which I assume will need to be undone for proper shimming. Any advice on what to do would be greatly appreciated. Should I leave it or make the contractor fix it?

Thanks!

[TheWindowNerd]

The frame width should be the same at top, bottom, and in the middle. You are correct they should have been shimmed at the time of setting.
Yes it should be corrected.
You are walking a tough line pointing out this error. In addition to unnailing the lenght of each window, if the fins were back caulked that to will need to be undone. This will piss off the crew and make you the bad guy. I would ask to speak with the owner or production manager at least. Stop all work till you get this resolved. You might ask for a new crew, they get pissy when called out.
No matter what you will now have to be the supervisor/inspector.

[Delaware Mike]

Ideally, the spacing would benefit from being uniform but keep in mind that rough framing is almost always performed as fast as possible rarely square and rough sills aren't typically perfectly level You do not want your new windows "pickle-barreled" at the meeting rail of a double hung or any other taller window like a casement. We composite shim the bottom of a new construction window atop the pan flashing membrane, and at the meeting rail. Nothing else on a vinyl window benefits from the 2" of vinyl window inside of the rough opening as one cannot flex the interior vinyl frame from the nail fin.

Keep in mind modern vinyl windows aren't doors with slabs that get slammed with constant frame torque if not screwed, shimmed, anchored, and foamed correctly. I'd take a level from the interior a check the jambs to see if they're true, or bowed inwards or outwards. It's common to "hour-glass" the middle a little in a little with over shimming to close weatherstripping gaps from the sashes to the master frame, however too much shimming will make the sashes pinch and not open and close nicely. You can tilt the bottom sash in too to check that contact area.

[Ricknez]

He may have used jamb adjusters that come with the window. They work well if the gap is 1/4 inch or less.
For replacement, shims are almost never used because of the built in jamb adjusters that are designed into the window which are also called “ jamb jacks”. This is assuming there is a narrow gap.

[TheWindowNerd]

the Op states "Every window frame is slightly wider in the center than at the top and bottom"
If the windows are hour glassed then either the jamb jacks were not used properly or they need to be shimmed.
theWindowNerds

[HomeSealed]

Seems to be the opposite of hour-glassed?

I'd agree, if the center of the window at the meeting rail measures wider than the top and bottom, that is concerning. The meeting rail area is generally the area of greatest air leakage on a double hung window, and lack of shimming (via actual shims or jamb jacks) in that area is problematic.

[TheWindowNerd]

Yup, sorry, as DM calls it pickle barreled.

[toddinmn]

I would also check the reveals at top and bottom by raising the upper sash slightly above frame and look for straight line between the 2. Do the same by lowering the upper sash. Great time to also check out flashing details.