Metal Roof - To sheet or not to sheet that's the question?

[ColchesterCabin]

On my build I like a lot of people are looking at putting on a metal roof. I was told by a contractor that there would be no need to sheet the roof before installing the metal rook. I told him I thought it would condensate he says if it is insulated and vented properly it would never condensate. Any thoughts?

[Squirl]

http://countryplans.com/smf/index.php?topic=11817.msg151843#msg151843

I remembered the topic from a few months ago.

[MountainDon]

Good memory squirl

Use sheathing, makes the roof structure stronger. It's a house not a barn, isn't it?

[offthegridcortland]

Mountaindon put it in the simplest terms.  Just to reiterate: plywood is one of the finest products made to resist racking forces.  After the first two screws or nails, each additional fastener creates new triangles- new points that would have to fail in order for the roof to shift.  Using metal roofing for that purpose would put a lot of stress on the roof and especially the fasteners which weren't really designed as a structural element so much as to hold the roof in place- this can cause leaks!  Like your foundation, your roof is a place to beef up, not lighten.

[offthegridcortland]

A note- using sheathing, (plywood), does dampen the rain on the roof sound.  Some people like that.  Some don't.  Consider a porch without sheathing for that rain on tin roof sound.  -Aaron

[NM_Shooter]

I could do without the rain on the porch roof sound at my house.  When sitting outside during a rare rain, it is difficult to hold a conversation!

Yes.... do sheet with OSB or similar.  The strength is vastly improved.  If you have to walk around up there you will be glad you have it.  Definitely worth the extra time and $$ to put it in. 

[offthegridcortland]

It also gives you a load-bearing structure when you eventually need to go up on the roof to inspect and/or make repairs.

[Checi]

A note- using sheathing, (plywood), does dampen the rain on the roof sound.  Some people like that.  Some don't.  Consider a porch without sheathing for that rain on tin roof sound.  -Aaron

Ahhh! My daughter was just commenting to me about how she likes that sound of the rain on the roof. The NY house we're in now has a quiet roof, unlike our FL house. She finds the sound comforting when she is warm and dry inside.

[MountainDon]

Sorry but to me the rigidity of the roof trumps over the sound that someone may enjoy. Then I can sit warm and dry inside and not wonder so much about what the next gust of wind may do

[rick91351]

Anything to take my mind off of or masks my tinnitus.   

[ColchesterCabin]

Thanks guys those are all awesome points. Especially the link to the old thread. I am not quite to that part yet of my project I think I will add the osb under the metal roof.

[ColchesterCabin]

Now lets put a twist on it. I was reading up and the new recomendation amoungst builders in my area is instead of using felt on the roof tyvek wrap the roof same as the outside walls pre-finishing. They say something about the tyvek breaths where as the felt doesn't. I don't know any thoughts?

[Don_P]

Felt breathes better than synthetics and can act as a hygric buffer.
Follow manufacturer directions.
http://www.fabral.com/technical#tech

[JRR]

Ditto ... I use felt.

[hpinson]

Having to deal with an old leaky metal roof on our temporary quarters, with no sheathing substrate... I hate going up there to do any work or fix leaks- it feels very unsafe. Sheath first if you can.

[Bill Houghton]

It also gives you a load-bearing structure when you eventually need to go up on the roof to inspect and/or make repairs.

+1