I am getting ready to install some Andersen windows in my garage. (Four awning and two casements.)
The building is 2×4 framing with 1/2″ cdx plywood , then 1″ rigid foam board.
Do I need to put 1″ solid wood around the window rough openings?
I’m thinking no. Just set and shim the windows as one would normaly and use longer nails through the nailing flanges, but never having set windows over 1″ foam, I thought I would check here first.
Replies
yes.... we just spent a couple miserable months working on a house framed & sheathed just like that...... with no solid blocking
everything creeped
the windows all sagged
you need solid blocking to install the windows
We are working on a similar project. Same problems. You realize most people would not agree with your recommendation...too much extra work.
But, I would never install windows over foam.
We cut the nailers out of the appropriate thickness of plywood. It really only takes a little extra work to do the job right.
Thanks Mike.
I have installed windows over 1/2" foam a few decades ago, but they were the old brick mold/1x nailer/ double hungs. Since just about everything now has nailing fins I wasn't comfortable with just the nailing fins an shims keeping everything where it is suppose to be.
I'll cut back the foam and use a couple of layers of 1/2" sheat goods as the nailing base.
I'm courious about the "creep" thing. I noticed that Hardi siding is allowed to be installed over "up to 1" rigid foam. Ever see a job done like that. Seems like you would get some serious creep or possible sagging.
time will tell on the hardie creep...Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
dave... just went back & re-read your post
your proposed install is worse than the ones we've been fixing
they had 1" foam with 1/2" plywood sheathing on the outside
the sheathing creeped and the windows sagged
your creeping would be accelerated
this is one of the reasons we do not use foam on the exterior anymore... by the time you install enough nailers for trim , windows & doors... there are too many thermal breaks
you need the solid blocking to properly install your windows & doors
Installing nailers shouldn't increase the thermal bridging any more than not having the foam sheathing at all. Your foam still thermally breaks all the other numerous locations of framing that aren't around doors and windows.
Wonder what the manufacturers recommend for this kind of thing. I'd never thought about it. While not a huge amount of work ... it's not minimal, either.
Curious why you would sheath on the outside of the foam?? Never heard of that. Sheathing relies on the friction connection to framing face as much as putting 'x' number of nails in it for its structural integrity.
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Curious why you would sheath on the outside of the foam?? Never heard of that. Sheathing relies on the friction connection to framing face as much as putting 'x' number of nails in it for its structural integrity.>>>>
you're right... and my BI wanted that connection... the T-straps were not in compliance with shear requirements
anyways
windows, trim, doors... all need good blocking
siding needs a good nailbase... thus the plywood on the exterior of the foam
BUT i will not use foam on the exterior unless it is treated with Borates... too much vermin living and moving thru the foam otherwise
so we moved the foam to the interior wall
then , on the advice of Tim Mooney, we dropped the foam all together
we do Mooney Wall..... or, if you want more insulation... we do Super Mooney wall
foam only goes in headers, dams, and cornersMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
I knew a guy once who didn't sheath but at the corner and everywhere else 1/2" foam ... or he did only angle bracing and 1/2 or 1" foam. Then wrapped w/ Tyvek. Said he liked being able to poke a nail to ensure a stud was there for siding (no he didn't do it everywhere!). He installed bevel lap siding. I don't think he ever had a problem w/ it.
Once you nail siding e.g. through foam, you should have a pretty secure connection. Guess I would avoid 'expanded' polystyrene and go extruded or polyiso ... more consistency and much higher compression strength. Just thinking out loud ...
Mike,What was your basic approach w the foam on the inside?2x4 wall w FG, 1.5" foam, VB, no blocking out windows and doors?Thanks, HarryAlso, my dad has a house (down the cape) w the foam on the outside.She's holding up OK. Its about 10 years old. The builder is a nieghbor -and now freind- of my dads. The builder said "never again".
last foam we did was 2x4 wall, 1" EPS foam, 3/4" furring @ 16"oc
the 3/4 furring also used as trim nailbase
now we just do Mooney wallMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Sorry for the dumb question, but what does sheathing creeping mean?
I have seen and worked on homes that had framing.... 1" foam... and plywood sheathing
the windows , doors, cornices, and other loads deflected the sheathing.. and it creeps down the side ..... just enough so the windows stop working, doors come out of plumb
foam details need solid blocking ... wether the foam is inside the sheathing ... or outside the sheathingMike Hussein Smith Rhode Island : Design / Build / Repair / Restore