Does a garage roof using SIPs need to have a cold roof on top of the panels?

Are they metal skin panels or OSB?

OSB

It's an interesting question. Seems OSB really needs the air gap to prevent rot resulting from interior air leaking past joints and condensing under the roof. But if your garage is not conditioned then it's a different scenario. Would it be a detached, unconditioned garage?

The garage will be attached to the house, but will be a non-heated structure.

Maybe someone else who has more experience with OSB panels will chime in, but I would think if it is attached to the house then you would want to continue the same venting air gap under the roof that you would use on the rest of the structure.

Although it's attached to the house, there is a mud room between the house and garage, so it's a separate roof from the house.

No heat should mean no warm humid air to condense. But I'd tape both sides anyway.

If insulation is not a concern, why would you use SIPs anyway?

I'm considering using SIPs for ease and speed of construction. The house will be a timber frame enclosed with SIPs. So if the garage can be put up at the same time as the house SIPs, I'm thinking that my labor costs will be lower in comparison to hiring a framing crew to stick frame the garage. I have to do a cost analysis comparing materials + labor for each method, thus, the need to know if a cold roof is needed for SIPs on a garage.

Posted By eweingarden on 14 Jul 2016 08:25 AM
I'm considering using SIPs for ease and speed of construction. The house will be a timber frame enclosed with SIPs. So if the garage can be put up at the same time as the house SIPs, I'm thinking that my labor costs will be lower in comparison to hiring a framing crew to stick frame the garage. I have to do a cost analysis comparing materials + labor for each method, thus, the need to know if a cold roof is needed for SIPs on a garage.

OK, I see the logic now, the short answer is no it's not needed,
however, you might want to consider doing anyway if you want to keep the fascia detail the same? or if you think you may want to finish it out at a later date as heated/conditioned space
or consider systems that don't require a cold roof

What kind of system doesn't require a cold roof?

Posted By eweingarden on 14 Jul 2016 11:12 AM
What kind of system doesn't require a cold roof?

metal skinned sips don't allow moisture to pass thru and is a good reason they are used in industrial cold storage, clean room and corrosive applications.

Thanks