My wife and I are having a Timber Frame/ SIP home built in NW Michigan. The builder is competent but not an expert on SIPs. I’m hoping to get the benefit of the experience here on the forum.
We plan to have board & batten siding on the exterior but I don’t know how it should be attached to the SIPs. It’ll be 1×10 fir or pine with 1×3 battens and we were planning on using DrainWrap. My preference is that it’s attached with ring shank nails directly to the SIPs. My web searches are a mixed bag; many advocate using horizontal firing strips, some say attach it with screws, a few say ring shanks directly to the SIPs will be OK. I don’t doubt that using firing may be the ultimate best method but obviously ring shanks directly to the SIPs is a faster/cheaper and causes a lot less issues with the windows and trim.
Can anybody with experience with B&B on SIPs help me out on this? thanks
Replies
bruce
How thick and what is the exterior sheeting on the sip panel?
Will the B&B be green (fresh, not dried)?
More details
Calvin -- Thanks for jumping in. The SIPs are polyurethane sandwiched between sheets of 7/16" exterior rated OSB. The total width of the panels are 4 1/2" thick. We're still nailing down (bad pun) the specifics of the siding but it will likely be kiln dried and either pine or doug fir. We're deciding between several sources and the thicknesses range from 7/8 to 5/8"
I can't help you on the B&B, but I have lived for 8 years in a home built of SIPs in a cold part of the Colorado Rockies. Our heating costs are quite low, but our SIPs are 8" thick. I wonder what the R value is of a 4.5" SIP. That seems a bit thin to me, even for your milder climate. You might want to check this out and perhaps see if there is a thicker option that doesn't break the bank.
Polyurethane SIPs have high R value
Bergsteiner - My panels are Polyurethane, the vast majority of SIPs use Expaned Polystyrene aka EPS or Styrofoam. Polyurethane is R7 - 8 per inch and EPS is R2 - 5 per inch. I mistated the thickness earlier. My panels are actually FOUR inches from outside to outside. This four inch panel is rated at R24 whereas one of the big EPS outfits advertises a 6 1/2" panel as R23.
This actually enters into my quandry about the siding since one of the reasons I went with the Polyurethane panel was the walls end up at the same width of a conventional 2x4 wall. I'm really hoping that it won't be necessary to fir out the walls.
It made me chuckle a bit when you said my "milder climate" because we think it gets plenty cold.
With B&B siding, you NEED
With B&B siding, you NEED furring to provide drainage channel behind the wood
Your 3.5" of poly will give you R24.5 and another R1 for the wood, making it an R26 assembly at most.
But if you seal/control infiltration at sills and above or at windows, you can be very comfortable
Siding nailed to sheathing
comes right off if you pull on it. Ring shanks will make little difference in 7/16" OSB. In your situation I would felt the building, install horizontal 1x3 or 1x4 furring, then attach the siding. I would nail the boards using a siding nailer and 2" ring shanks, and then screw the battens using hot dip galv or stainless screws. The battens are what hold B&B siding on, the nails in the boards do little.
I would not screw siding directly to the SIPS because I suspect the screws would wick moisture along the thread into the OSB. If you let the OSB get damaged over time, your house is totaled.
Bottom line is furing strips are needed
Piffin and davidmeiland -- Thanks for your advice. I'm not surprised you are advocating using firing strips. I was holding out hope that the structure of a SIP would adequately hold nails and having grooves on the back of the siding boards and using drainwrap the water would drain away. Furing strips sound like the surest bet. thanks again for weighing in.