Sheathing: Alternatives to OSB and Plywood
Wondering if anyone has recommendations for good structurally insulated panels as an alternative to OSB/Plywood sheathing? I’ve been looking into various products which provide a WRB, Air Barrier, and continuous insulation; however, I find most of them use Thermoply or something similar as the structural component which doesn’t appear to be a very robust product.
ZIP seems to be the default to land at if I’m stuck paying the current prices of OSB but I’m looking into alternative materials that may meet or exceed OSB/CDX given the current high price environment.
I have inquiries out with ROK-ON and Armorwall and wondering if there are any other recommendations out there
EDIT: I originally titled this as SIPS instead of SIS. Please note this is about Sheathing options as replacements to OSB/Plywood.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Deleted
There's a building going up down the street from me. The SIPs were delivered last fall and sat in a stack on the ground all winter. This month, it took the crew well over 2 weeks to get the walls up. I wonder if the panels were screwed up after all that exposure. They managed to defeat the whole purpose of pre-building panels indoors.
If you were going to do SIPS, I believe the best SIPS would be with a polyurethane core instead of a polystyrene core. The polyurethane cores are fire resistant and don't melt when exposed to 300F+. They are also stronger and you can go thinner on the thickness and obtain higher R-Values vs polystyrene.
As mentioned, you do have to get all the details right to prevent issues. Also, as mentioned, SIPS are not the most inexpensive way to build either.
Time wise, SIPS have an advantage of speed as you are able to get the entire wall or roof assembly together in days, not weeks or months. I have an ICF wall and SIPS roof and my roof was completed in just 1 day. I had a completely insulated home, with 2' overhangs/soffits in just 1 day. The time/cost to stick frame or truss the roof, then frame out soffits/overhangs on all sides, then sheath the roof and soffits, then insulate the roof/attic. It would have taken weeks or even months based on crew availability.
Will,
From you title you are getting answers about SIPs, but reading your question I think you are asking about insulated sheathing, which is a different thing. It might be worth while changing the title of your thread.
Yes! I goofed up there, thank you.
Insulated nailbase used for roofing is commonly available, but most still uses OSB as the nailing layer. It would/could work as wall sheathing depending on specs. There aren't that many choices for structural sheathing. They're pretty much limited to ply/OSB, Thermoply, and gypsum. I am not aware of any gypsum sheathing products with pre-applied foam insulation. Rok-On and Armorwall are both interesting products, but I have no familiarity with their use.
You could consider using let-in bracing for shear loads, so that you can go ahead and use any insulation panel in lieu of structural sheathing. Some of the Thermax products are designed to be WRB, air barrier and vapor control layers in addition to insulation. And in residential construction, many people use EPS/XPS insulation with a plastic facing as WRB, air and vapor control. There are more and more options out there to replace OSB, but they are rather new and you might be breaking new ground with your contractors, designers and code people.
Do you have any recommendations for exterior Gypsum products without insulation or experience working with the material?
You are looking for Denseglass or Securock. The 1/2" stuff is much cheaper than OSB/CDX, 5/8" can be used for rated assemblies. With the right nail pattern it can be used for bracing walls.
It is pretty easy to work with, goes up quick with a roofing nailer or auto feed screw gun and the seams can be taped with something like 3M 8067.
Score and snap like regular drywall. It is heavier than CDX and does itch. Much higher perm than OSB or CDX. It won't hold nails, your siding needs to go into the studs.
Some folks, like Randy Williams, are proponents of fiberboard sheathing—something he recently wrote about: Upgrading Performance with Fiberboard Sheathing.
Thx folks. I'll look into recommended options. While I'd love insulated sheathing to skip a step I suppose the ultimate goal is finding alternatives to OSB/Ply at a better price considering how sky-high it all is right now.
There's a relatively new product out made by Huber called Exacor - It's a magnesium oxide panel thats structural, unlike most fiberglass / gypsum panels. I'm not sure about the availability or price, but it's vapor permenance is right around 15 perms, it has about 70% of OSB's shear capacity at a tight nailing schedule, and it can't rot. It requires a separate WRB, like OSB and plywood.