Pole Barn Question - OSB or not for Roof

[PoleBarnGuru]

Question #2: House wrap
Would there be any advantage in wrapping the frame with Tyvek prior to installing the metal? I am thinking that I will insulate the barn next year and the Tyvek might help. I live in NC, so the walls will get warm in the Summer sun. The additional cost would be minimal, but I am not sure about the impact of putting insulation right against the metal without some type of barrier. Houses have OSB and wrap to minimize vapor. Any thoughts or suggestions?

Thanks for your help.

Go with the housewrap in the walls, if you intend to insulate them later. For more on this subject: How to Design a Climate Controlled Pole Building

 

[PoleBarnGuru]

If your using 26 GA or 24 GA, I wouldn't use OSB, but if your using 29 GA, I would think you might be better off with OSB. 29 GA metal has very little structure of it's own. Obviously this depends on the type of panels as well; Rib-12, rib-6, standing seam, corrugated...

29 gauge steel roofing will do everything your need it to do structurally. Read more: Let's Talk Steel Thickness

 

[PoleBarnGuru]

As for tyvek, years ago, when I built metal buildings, are insulation came with a tyvek type material facing the inside of the building, with bare fiberglass agaisnt the metal, held in place by being pinched between the purlions and the metal panels. The rolls where 6' wide, so they did 2 panels per roll.

The referenced product is Metal Building Insulation: Metal Building Insulation in Pole Buildings Part I and Metal Building Insulation in Pole Buildings Part II

 

[PoleBarnGuru]

Have you priced a PEMB? (Pre engineered metal building) They are surprisingly low cost for the square footage.

Pole buildings are nearly ALWAYS a better value than an all steel building. Myth Busters and All Steel Buildings

 

[randy41]

OSB=old sh---- board.

 

[radioman]

oh boy - if you go with OSB, then go with shingles. shingles are not cheap. As for house wrap, I might use it if I built here in Northeast due to winds and no insulation.
Look at the long term picture. you are more south and I'd be more concerned with keeping it cool or heating up much during the day. If you went with purlins and sheet metal roof, no house wrap - I would spray foam the WHOLE building . just a half inch of foam is enough to stop sweating. It would double as a vapor barrier, and insulation. If you do go this route, you would need to cover up the walls so you can prevent fires if foam catches spark.

 

[CentralNC]

If using osb, then 30# felt needs to be installed on top of the osb and under the roof steel. 7/16" osb prices are currently down to around $11 per sheet (roughly 35 cents per sft) and reflective insulation with adhesive pull strips attached is about 1/2 of that. (see Buy Reflective Insulation | Foil Insulation | Radiant Barrier | Vapor Barrier as an example)

Even 29 gauge steel is plenty strong enough to carry any imposed loads, without the osb. The osb will add less than two psf of weight to the roof, so the difference in truss costs would prove negligible. And no, the roof will not sweat with the osb.

I appreciate the thoughts and suggestions on the pole barn. I think I will add OSB under the metal roof. I had planned on using trusses every 4'. Your comment has me thinking that maybe I should add trusses? Maybe standard 2' apart like a shingle roof?

 

[PoleBarnGuru]

I appreciate the thoughts and suggestions on the pole barn. I think I will add OSB under the metal roof. I had planned on using trusses every 4'. Your comment has me thinking that maybe I should add trusses? Maybe standard 2' apart like a shingle roof?

I'd be more inclined to recommend placing sidewall columns every 10' going with a 2 ply truss at each interior column, single truss on ends. Use 2x6 on edge for roof purlins.

For information on widely spaced trusses: Pole Barn Truss Spacing

If the plan is to place trusses every 2' and sheet directly over them, then screw steel to the sheeting, you will need to use 5/8" cdx plywood, as osb will not hold the screws. This will change the cost factors significantly.

 

[PoleBarnGuru]

oh boy - if you go with OSB, then go with shingles. shingles are not cheap. As for house wrap, I might use it if I built here in Northeast due to winds and no insulation.
Look at the long term picture. you are more south and I'd be more concerned with keeping it cool or heating up much during the day. If you went with purlins and sheet metal roof, no house wrap - I would spray foam the WHOLE building . just a half inch of foam is enough to stop sweating. It would double as a vapor barrier, and insulation. If you do go this route, you would need to cover up the walls so you can prevent fires if foam catches spark.

For information on spray foam insulation: Spray Foam Insulation: What's the Stink? and Lawsuits Amass for Spray Foam Insulation

 

[DaveOmak]

If you spray foam the interior, for insulation and moisture barrier, there is a polyurethane foam that is rated for fire retardant qualities... and it stops air infiltration....