About to install a SIP roof system for the first time. designed and pre cut from the factory; 8×24 ft panels;56 ft roof length. the concern is…. if the first panel installed (or first on each side)is slightly off,by the time the last panel in the 56 ft length is put up,it may be off by a mile! what technique is used to insure the first panels are EXACTLY on. with gluing and screwing with these massive screws it seems that once theyr on,… theyr on. is there anyone out there that has been through this before and can give words of wisdom.
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If you read the manufacturer's installation instructions they will, or at least should, say how the pannels are trimmed to fit if need be. Most SIP installs require fine tuning since it's still construction not an exact science.
Typically this is trimming the osb so the pannel is the right size and recessing the foam so the edge stiffeners have enough space to fit correctly.
Reading worst case scenarios, the worst thing you can do is not seal the edges as per manufacturer's specs. If moisture gets into the osb it doesn't have anywhere to go. If you are worried about anything worry about that.
If a pannel needs a little extra room it's ok to have a slight gap between osb edges, say 1/4" or so. More than that and it depends on how critical the joint is. It may be that you simply need a wider joint board or joist. For instance if you need to come up with a wide gap, I'm confident the manufacturer would okay a wide flange I-joist in place of a narrow flange one, or a doubled 2x glued and screwed with structural screws instead of a single.
Did I mention how critical it is to seal the edges completely? If the manufacturer says you need 5 cases of their special caulk/construction adhesive, then you are wise to use at least that much. Same with sealing the seams with vycor or similar. Use expanding foam on any penetration such as wiring and seal, seal, seal till the cows come home or all the gaps are closed.
Plan your vent penetrations now and if you have to cut a hole in the SIP makes sure it was accounted for in the design or call the manufacturer with what you need to do. They might say to just drill the hole and stub the pipe through, or it may need to be opened up to a square shape and additional edge supporting 2x material glued and nailed into place.
Where the manufacturer says to nail, you should nail, where they say to screw you should screw. Joints may seem tight, but they rely on the large number of nails to obtain the strength in the shell. Joints not nailed will open up over time and let moisture in.
If something doesn't make sense let us know. It's hard to draw on simple carpentry experience with some SIP issues since they aren't 100% intuitive to figure out, but once you hear a fix it will, or should, make sense.
If in doubt call the manufacturer since you have to install them per their specs to retain the warantee. In a worst case senario you don't want to be the one picking up the cost of replacing a pannel simply because you used pl10 construction adhesive instead of the foam friendly one, or other similar deviations. From what I've read, most roof pannels that need to be replaced are due to improper installation, or more precisely, installation practices that the manufacturer didn't or wouldn't authorize.
In a way SIPs are very simple and in other ways they need to be installed according to very exact practices.
Best of luck and shoot us some pictures and the name of your SIP manufacturer.
Beer was created so carpenters wouldn't rule the world.
I haven't installed one lately. but I did install one maybe 13 or so years ago. I don't think things changed too much since then. If I remember correctly check for square, snap your lines and cut, seal and screw as per manufacturers specs. Have at least three healthy bodies around to move the beasts. I remember having a Prazi beam saw but we also had skillsaws and a hot wire foam cutter that worked well too.
Do a serach here at BT. I seem to rember a sip roof failure where the seams were telegraphing through the roofing material. I might be mistaken though.
ckt.
Trimming panels is a normal part of every SIP Job.. while great care can be used sometimes things just don't work out as designed.. with plywood they cut it and nobody notices it but when SIP's are installed everybody focuses on it..
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Think of SIP's a really thick plywood and there is no problem..