Metal Roof

[Redoverfarm]

OK the manufacturer's don't recommend placing metal roofing on a slope less than 3/12.  Just like everyone else " I just need a little more".  Is it the water back up that they are concerned with or the weight load or combination of snow/water.  Maybe Bob will pick up an enlighten me or anyone else who had installed one on a lesser pitch. 

[glenn kangiser]

Wierd-- I built about 300 steel buildings with either a 1/12 or 2/12 pitch depending on the brand.  I'd say they are telling you that to limit their liability.

Get strip caulking for all the seams -- flash and caulk properly and I don't see how it could leak except in the case of poor craftsmanship. 

[MountainDon]

I don't see weight of water, etc being a problem. The metal probably weighs less than roll asphalt roofing that's recommended for low pitches. I know it weighs less than asphalt shingles.

Glenn may be onto the real reason.

[John Raabe]

I think you are getting the standard low pitch rule. Do as Glenn suggests. The seals will most important if you have some heavy wind driven rain and/or ice dams in the winter/spring. The lower the pitch the less gravity a leak has to overcome.

[PEG688]

   Use ice and water seal under it , also called peel and stick.  The whole roof that is . The tricky parts  are at wall step ups , if you have any, and wind driven rain , IF , it can stack up / be blown up and under any counter flashings.

  Extend your lower eave line / facia over hang at least 2 " so water can't capalary / wick back up and get to the facia and or roof sheathing.  In other words a nice long drip path right into the center of the gutter. 

  And Glenn and John ideas as well.

3/12's as low as we've done.

Any vents or skylights ? Those could be trickie. On that low a pitch MTL not recommended .

If you have to have any of those you might need to rethink or relocate them to another section of roof , IF,  possible that is.

   

[Redoverfarm]

Peg I am going to use perlins instead of sheeting on the porch roof so I guess storm/ice guard is out.  The lesser porch roof will be placed under the overhang of the main cabin roof(10/12).  There will be a 10-12" drop from the roof edge of the 10/12 to the porch roof. Maybe I can get a picture posted that will illustrate what I am doing.  Well I am up to the mountains to work on the soffit. This has to be done before the roof is addressed anyway.

[glenn kangiser]

If there is snow it may try to dam and water could back up and flow over the high end so I would get external rubber seals and preferably a longer leg flashing from the wall out.  The rubber seals go over the sheeting and under the flashing.   I would also caulk them top and bottom.   If no snow that probably would not be as much of a problem.  The buildings I did were in a no snow area.  The steel roofing company should have seals available as an accessory.

Most 26 ga. or 29 ga. high tensile will span 4 feet at 20 lbs psf.  Purlins at 2 feet would probably take that up to 40 psf.

[PEG688]

I'd say sheet it and use the Ice and water shield.

If your in a snow area you will have snow slides off the main roof and the metal alone will not take that without support , it's cheaper to do it once right than it is to do it twice.

[Redoverfarm]

Peg This is the area that I was speaking of.  The 3/12 or lesser will be put up under the overhang of the main roof.  There will be a 10-12" drop from the main roof to the porch roof.  The porch roof will start approximately 12" back from the edge of the main roof.  If I would use a pitch diverter or flashing then my pitch would have to be less than 3/12 which will not give enough headroom on the rafter tail end.  By using a 2/12 and a rim joist for the rafters to sit on I can probably live with the distance.

Another alternative would be to use a pitch diverter with a narrow top(2 or 3" elevation) and a seal on the diverter half the distance of the overhang attached to a 2X2 or 2X4 filler between the porch roof and the soffit of the overhang. Make sense?

I wanted to stay away from sheeting and use perlins 16"OC.  I could however use sheeting for the upper 4' to reduce the damage by the snow/ice slides.

Hope these photos help

John