Finally started on my Texas pole barn!

[ericstac]

Eddie, What metal roofing are you talking about that doesnt need the OSB? I am familiar with residential construction and only know of the expensive metal roofings and was really wanting to go with a metal roof on our new barn but not at that expense. If you could tell me what metal roofing I could use that is cheaper for the barn I would appreciate it. Thanks.

 

[em14]

Eddie - I am no roofing expert but I know there are metal roofs going on structures just as ericstac is doing yes moisture is a concern. But it appears to be considered to be min. It seems there is a bit more concern about the moisture when "lattes", i.e., 1 x 4, are placed horizontal across the roof structure and the metal roofing is fasten to them. Then when the moisture collects on the bottom of the metal and it runs down it strikes the latte and has no place to go. There are some nice web sites about metal roofing and here is one: Metal Roofing Materials | Metal Shingles | Best Buy Metals (Edit: Perhaps you and I are use to building barns with metal "5 V Crimp Metal" roofing where we nailed to the purlins and the roof had no plywood or osb used!)
Leo

 

[Megado]

Eddie - Thanks for the response and willingness to cover the basics for not only myself but for all the others on TBN as well. I'm basically learning as I'm going along and I'm certain I will be making mistakes along the way so your insight and shared knowledge is always welcome.

As for the sagging 2x12's...I honestly cannot tell you if I placed the bow up or the bow down on the few that have sagged so badly. For the one's that the bow was detectable, I do know that I put the bow up when I installed them. For the others though, there was little or no bow detectable so I may or may not have installed them correctly. I'm thinking that I'm going to remove them, flip them over and then reinstall to see if they will settle back into place. From your experience, does that sound feasible or will I be wasting my time?

As for the metal roofing and using OSB decking, like SteelDust before me, my reasoning behind wanting to have decking underneath the metal roof is due to the amount of walking I will be doing on the roof as I finish the barn. Having a solid surface below me and not worrying about where I step will provide piece of mind. I have the same "Classic Rib" metal roofing w/o decking on the two houses on our property, and to be honest, it's a little unnerving when I walk around on those roofs. I'm always concerned about where I step and if I might end up stepping where I shouldn't. Even though it may be overkill for a barn, I'm willing to do the extra work of installing the decking for the comfort level and piece of mind of knowing I've got a solid deck below me.

I did do a lot research on the potential moisture problem. In fact, I spoke directly with the metal roof manufacturer of the material that I will be using (Metal Sales, Inc. out of Temple, TX - Metal Roofing Manufacturer Commercial Metal Roofing Metal Siding Manufacturer Indiana Metal Roofing Manufacturer Indiana Commercial Metal Roofing). Their recommendations were to use decking w/ #30 felt underlayment as a moisture barrier with the metal applied directly on top of the felt. They did not recommend the use of 1x4 "lattes" and felt doing so actually caused more problems due to the air gap between the metal and the felt which actually promoted condensation.

Bottom line...I'm probably going overboard with some of the extras for just a simple ol' barn, but I'm ok with doing so. I'd much rather be guilty of overbuilding than to deal with the results of underbuilding.

Jim H.

 

[EddieWalker]

I agree that the OSB gives it more strength and stiffness, and stronger is always better!!!!! With the use of felt paper, you will have a very good roof.

Rolled insulation foil over the purlins keeps the condensation off of them if that's a concern. I can't speak for very many buildings, but when there is a problem with construction, it becomes fairly common knowledge. I've never head of purlins rotting out from the amount of moisture they get from the condensation off of metal roofs.

With or without the decking, the real trick to walking on metal roofs is to wear white soled tennis shoes. For whatever reason, the white colored rubber holds allot better then any of the black ones that I've owned or tried. Be sure the soles of your shoes are clean too. It makes a big difference with just a small amount of dust as to how much traction you will have. Also be careful of early mornings on the roof. Morning dew is VERY slipery.

Eddie

 

[EddieWalker]

Eddie, What metal roofing are you talking about that doesnt need the OSB? I am familiar with residential construction and only know of the expensive metal roofings and was really wanting to go with a metal roof on our new barn but not at that expense. If you could tell me what metal roofing I could use that is cheaper for the barn I would appreciate it. Thanks.

I buy my metal from Muellers, which is a chain here in Texas and other states. They are very good and I highly recomend them. I've done several barns, quite a few sheds and my own house with their metal. All of them have been what is called an R Panel. It's a very common type of metal that has three high ridges and several small ones between the high ones.

One of the advantages to metal roofing is that you use fewer trusses. Depending on what you use for purlins, is how far apart you can space your trusses. Less trusses, less money. I build mine on 4 foot centers. This allows me to use 2x4's for purlins on the flat. You can go 6 foot centers and use 2x4's on edge and at 8 feet centers, you can use 2x6's on centers. Then for every 2 feet width, you go up a size in lumber. That's a general rule of thumb and not code or anything engineered. Snow loads wont apply to that either, it's just for us southern states.

Then you just screw the roof panels to the purlins. With screws, you put them through the flat part of the metal so when thight, there is no gap. There has been some discusion on here about screw placement, but that's how I do mine and how Muellers recomends it to be done. Then you put sticky tape on top of the end peak and lay your next panel on top of the previous one. It's fast, easy and effective.

Here is a picture of my wife on our roof when we installed our roof. This was her first time, so she was nervous at first, but by our second panel, she had it down and we got it done fairly quickly. I carried the panels to the house, slide them up to her and then she held them in place while I climbed the ladder. we put it into position, measured for square and I held it in place while she put in a few screws.

Areas of metal over a living area or heated and cooled space should have some rolled insulation under the metal and over the purlins. Areas that are exposed and no heated or cooled don't have to have it, but it's nice if you want to spend the money. I didn't spend the money at the time, but wish that I had now. My house is the part that's already covered, my shop is the area in the picture that is not covered yet.

Eddie

 

[EddieWalker]

There are some nice web sites about metal roofing and here is one: Metal Roofing Materials | Metal Shingles | Best Buy Metals (Edit: Perhaps you and I are use to building barns with metal "5 V Crimp Metal" roofing where we nailed to the purlins and the roof had no plywood or osb used!)
Leo

Leo,

I glanced at the website, but didn't see anything that supported your claim of the purlins being an issue with moisture. I won't deny that they get when when condensation forms on them, but with good peak vents and air flow, that is a very minimum amount of moisture that dries up very quickly. My concern with OSB is that it has to have the felt paper to protect it from the moisture, or it will sit there for an extended period of time and not dry out, which will lead to rot, mildew and eventually, failure. With the use of felt paper, this shouldn't be a problem, but I honestly don't know for sure what happens in there either.

You either want lots of air access to the underside of your metal roof, or you want it sealed up solid. Spray foam is the best for this, but rolls of insulation designed for metal roofs works too.

That said, there are metal styles that lay totally flat and require OSB or some other decking underneith. I've seen them installed on commercial buildings, but don't have any personal experience with them. The difference is that they do not have any air cavities in them and when installed, there's no place for condensation to form.

Remember, sweating roofs or buildings is just a generic term to explain condensation. Metal does not sweat, it collects condensation from being in the middle of two different tempatures when the water in the air is at saturation level. The colder the air, the less water it can hold. The water in the air forms ont the surface of the metal, or whatever is around, and you have condensation. Same with dew and fog.

Eddie

 

[weldingisfun]

I did do a lot research on the potential moisture problem. In fact, I spoke directly with the metal roof manufacturer of the material that I will be using (Metal Sales, Inc. out of Temple, TX - Metal Roofing Manufacturer Commercial Metal Roofing Metal Siding Manufacturer Indiana Metal Roofing Manufacturer Indiana Commercial Metal Roofing). Their recommendations were to use decking w/ #30 felt underlayment as a moisture barrier with the metal applied directly on top of the felt. They did not recommend the use of 1x4 "lattes" and felt doing so actually caused more problems due to the air gap between the metal and the felt which actually promoted condensation.

I got the metal from these folks for my barn as well. No OSB used. Fastened directly to the purlins. No sagging.
Second to Eddie's recommendation of being careful in the AM with the dew on the roof.

 

[Megado]

Thanks guys. Perhaps I should take the opportunity to clarify that my inquiry to the manufacturer was to get their recommendations if I chose to go with decking. Should I use lattes or nail directly on top of underlayment, what type of underlayment did they recommend, etc, etc.

Also...when I do get around to installing the roof panels, I will be nailing through the decking and directly into the purlins. The OSB does not have the holding power to do the job alone.

Jim H.

 

[SteelDust]

Thanks guys. Perhaps I should take the opportunity to clarify that my inquiry to the manufacturer was to get their recommendations if I chose to go with decking. Should I use lattes or nail directly on top of underlayment, what type of underlayment did they recommend, etc, etc.

Also...when I do get around to installing the roof panels, I will be nailing through the decking and directly into the purlins. The OSB does not have the holding power to do the job alone.

Jim H.

The manufacturer of my metal roofing also recommends 1/2" decking with 30# felt as an underlayment. I did ask about the use of OSB, they said it was acceptable but not ideal. I asked if the warrnty would still apply if I were to use OSB, they told me that it would. But, like you, I am also driving 1.5" metal roofing screws though the metal, through the OSB and into the purlins.

 

[Megado]

The manufacturer of my metal roofing also recommends 1/2" decking with 30# felt as an underlayment. I did ask about the use of OSB, they said it was acceptable but not ideal. I asked if the warrnty would still apply if I were to use OSB, they told me that it would. But, like you, I am also driving 1.5" metal roofing screws though the metal, through the OSB and into the purlins.

After rereading what I had writting previously...I should probably clarify that I too will be using 1.5" metal roofing screws.