Best way to insulate metal sided pole barn?

[SteveBenson]

I recently built a 34x48x10 center isle horse barn of typical pole construction (8' pole spacing, truss roof 4' spacing, 2x4 girts/purlins 2' spacing) with 29 ga. steel roof and siding (Fabral). This was the first pole barn I’ve built and I didn’t have a lot of outside experience to draw on, except from the lumber yard I bought the barn “kit” from. The “kit” consisted of lumber/trusses (appropriate for my size building), siding, and basic 2-page pole building plans.

I insulated the roof to prevent condensation (live in Northeast where humidity is a factor, plus moisture from livestock) and to keep the barn cooler in the summer and warmer in winter. I didn’t need much of an R value to prevent the condensation so I went with 1/2” foam insulation board (R4) that had thin foil on one side and thin plastic film on the other. I put the 4x8 sheets of insulation (metal foil side down) between the purlins and metal roof then fastened the roof down. Performance-wise, I’m happy with the results. Condensation is not a problem even with snow on the roof and the barn stays very cool in the summer. The problem is that I think I got some compression in the insulation when I screwed the roof down. When sighting along the roof it has a slightly wrinkled appearance. It is more apparent when the sun is out and low throwing shadows off the ribs of the siding. I know the trusses where straight before I sided the roof and it’s more wrinkly, not a bulge like you’d expect if the roof wasn’t straight. The side walls, which I didn’t insulate, are as flat as a pancake. The wrinkle is really kind of subtle and I’m probably the only one who has ever noticed it, but since I built it I do.

I was wondering if anyone out there has better suggestions on insulating metal sided barns. Also, any opinions on nailing vs. screwing metal siding. I did my siding with screws, but I’ve heard some say that nailing is better as the nails are driven thru the rib, where screws go in the valley and are more likely to leak. I wonder if there would be less of a chance of compressing the foam insulation with the nailing method.

 

[cowboydoc]

Steve,
When I insulate the roof I just use the insulation that you can roll out from one side to the other. It's alot quicker and you don't get the rises that you spoke of. As far as nails vs. screws almost everyone I know does the screws. If you ever have to repair anything it is sure alot easier to do it that way than to try and qet nails out. You can also screw on the rib. I do it that way and always have. I also don't like the idea of the screws being in the valleys.

 

[cedarranch]

Steve, I am no expert on metal siding/roofing but I have built several pole barns, a carport, and roofed our house. I have used both nails and screws and nails go a lot faster than screws. They both seem to seal fine - never had a leak in years. Use nails with the 'rubber' washers. The nails with 'lead' compression heads don't seal as well. I have always used the roll out insulation like cowboydoc mentioned.

 

[njrqs]

Steve

Screws are used exclusively over here and ALWAYS through the rib not the valley !

Cheers

 

[cowboydoc]

Believe it or not Neil they actually tell you to put them in the valley!

 

[DVerbarg]

The only time I saw screws in a valley was on a roof that had problems lifting. Apparently moisture was getting in and slowly rotting the wood around the screw threads and allowing the roofing to "lift" during wind storms. This happened over many, many years.

It does take a little extra effort to put the screw through the rib but is well worth the effort.

 

[SteveBenson]

That's right. The Fabral docs state that nails should be driven thru the rib and screws should be in the valley next to the rib.

CowboyDoc. I don't think I've ever seen the type of insulation you mentioned in any of the barns I've been in around here (and I'm always looking at such details). What kind of insulation is it, how thick and what kind of facing. Do you roll it out in the same direction as the panels (up/down), or across the panels (left/right). Does the insulation sag at all between the purlins or do you stretch it tight?

One problem we had with the 4x8 sheets is that the panel is 3' wide and the insulation 4', which required stretching an extra 2' over on every 3rd panel or so.

 

[cowboydoc]

Steve,
This stuff is great. You just roll it out tack it down and it stays in place forever. You can do a whole roof in no time at all. You roll it across the purlins so it would the same way as the tin. It's just a plastic type facing and is about 2" or so thick. It compresses to near nothing with the tin on it.

 

[Corm]

re positioning nails or screws in the valleys instead of the ribs - The explanation for this that has been told to me by a couple of local contractors is that screwing metals roofs thru the ribs tends to spread each sheet out as most folks tend to give each screw an extra turn or so to make sure it is tight, and as a result push the rib down, which has the effect of spreading the sheet (hope I explained that well enough to be understood..). The rest of the story goes that nailing in the ribs is O.K. because most folks won't set a nail hard enough to spread the metal sheet (typically to set a nail hard enough to spread a sheet you will dent the metal). Like I said, this is what I've been told by a couple of local contractors....

I've done roofs thru the years using both methods, and none of my roofs have ever leaked or blown off, but I did have a problem on the first roof I did where I screwed thru the ribs. You do have to be careful not to make 'em too tight! Once I learned the correct 'feel', I had no more problems. For what it's worth, if I ever do another metal roof, I will screw it thru the ribs using screws with rubber washers.

Corm