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will02 01-18-2012 05:15 PM

installing a metal roof on a shed
I am going to be building a 12' x 24' shed with a 12/12 roof pitch and the plans call for an asphalt roof but says you can go with a metal roof which is what I want to do. The roof rafters are 2x4 16" O.C. Obviously If I were going with asphalt shingles I would be putting down plywood, but since I'm not, do I still need to put down plywood and then install the metal roof over that or can I save $ and install 1 x's perpendicular to the rafters or will the 2x4's 16" O.C. rafters be sufficient enough to just put the metal on top of them? I live in Texas so I dont have to worry about snow. Also this will be my first time installing a metal roof so any other tips or tricks would be appreciated.


titanoman 01-18-2012 06:21 PM

You definitely need more than just the rafters themselves.
You can use 1x skip sheeting, but you must run diagonal laterals on the underside of the rafters and 45's on the gable ends.

will02 01-18-2012 07:07 PM

what do you mean by 1x skip sheeting is that basically the same thing that I mentioned earlier, about using say 1x4's to run across and sit on top of the 2x4 rafters.

mae-ling 01-18-2012 07:13 PM

Yes 1x4 every 16" (some go 2') apart on top of the rafters. Also need 1x4 on the angle under the rafters to provide bracing because there is no sheeting to do it.
I stack my sheets on the ground, say 12 at a time. measure the centers of the 1x4 on the roof. and transfer them to a 1x4. make sure you do this for both sides of the roof. as they can be different. and depending how you overlap your sheet the top on one side is the bottom on the other if you start at the front of the building for both. This acts as a jig to drill all holes evenly. I use an double ended drill bit I get at the auto store. It is 1/8" and tougher then normal bits.

Windows on Wash 01-18-2012 09:35 PM

Battens or Purlins.

No need to sheet the whole thing as mentioned.

joecaption 01-18-2012 09:40 PM

If you use an impact driver with a 1/4 magnetic bit you will not have to do any predrilling.
Once you've tryed an impact driver you'll find all kinds of uses for it.

will02 01-19-2012 12:31 PM

Do you guys recommend I use the asphalt paper under my 1x4 battens as shown in the picture above?Also I've looked around and have had a hard time with finding some good clear instructions on flashing around the metal roof.My plans call for a 6" overhang so I'm sure i'm going to need to add flashing, does anyone know of any good sites or threads where I can find this info or should I start a new topic? Thanks for all the help

Tom Struble 01-19-2012 12:41 PM

yes,it will help with controlling condensation,which is why i would also recommend you install sheathing,for the simple fact that it will protect the felt from damage

will02 01-19-2012 02:57 PM

2 Attachment(s)
So Tom just so I'm clear your suggesting I first apply 4x8 sheathing, then apply the asphalt paper, and finally the metal roof, is this correct? I've taken some pictures of my fathers old shed and this is the type of metal that I wanted to use on mine. As you can see from the pics his shed has no flashing, should there be flashing under the roof metal and running over the 2x4 batten to shed water? Also would I still need to use battens on top of the asphalt paper to keep moisture from building up under the roof metal as you can see the metal I'm wanting to use is flat in areas and I was just concerned about moisture build up. Thanks

Tom Struble 01-19-2012 06:11 PM

3 Attachment(s)
i used metal on my shed,i attached directly to 2x purlins i made the mistake of installing no paper under the metal:( at times during the year i get condensation forming on the bottom of the metal

as others have said you don't ''need'' solid sheathing,but i think you can achieve a better drainage plane and protect the felt from being damaged underneath using it than if you install the felt directly to the rafters or to the purlins

you absolutely should install a drip edge,i prefer a projecting type that allows the panel bottom to ''wrap around'' it will help with wind loads but your panel manufacturer may have a different detail

on a shed roof i don't think you need sheathing and purlins,just sheathing and 30 lb felt should do ya,some manufacturers want an additional layer of rosin paper to avoid the panel adhering to the felt and to help absorb condensation

start reading at page 31

OldNBroken 01-19-2012 06:33 PM

Tom, painted/primed metal doesn't sweat nearly as bad as galvanized.

will02 01-19-2012 08:07 PM

Thanks Tom that had alot of helpful info on it. According to their instructions the 5v crimp metal roof, which is the same metal roof that my father has on his shed was supposed to have decking under it, but does'nt it just has battens spaced 24" O.C. but it was already like that when he bought the place.Looks like I've got me another project after mine. again thanks for everyones help

mae-ling 01-19-2012 10:51 PM


Originally Posted by joecaption (Post 827400)
If you use an impact driver with a 1/4 magnetic bit you will not have to do any predrilling.
Once you've tryed an impact driver you'll find all kinds of uses for it.

Pre-drilling your holes does a few things.
1. It is actually faster as you do a bunch of holes at once.
2. It makes everything line up and look straight and nice.
3. You can reach over and put a screw in, when pushing the screws through the metal and not pre-drilling you have to be over top the hole and dead square to the metal or the screw will skip and not go in.
4. Very very rarely with just pushing the screw through the metal you can get a burr that will slice the gasket on the screw and cause it to leak.

Luckystiff 10-05-2012 09:12 AM

Wood shed/carport
I'm building a wood shed lean too and a carport and was thinking of putting on a metal roof.I wont need sheating? I was just going to strap the rafters and screw the metal roof to the rafters. because both structures are open on all sides with plenty of vetillation?

Brad Tombs 10-19-2012 09:21 AM

From central NJ, any recommendation on a metal roof panel supplier for small shed?

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