Replies

1. 
   popawheelie | Jan 10, 2008 03:51am | #1

   I'm putting on my first steel roof soon. I have it ordered. From what I understand a steel roof with open lumber underneath is fine. The fasteners tend to leak a little but it's not an issue because of air circulation under the roof. There are ways to put this off with better fasteners. But the steel panels shrink and swell a lot over their length

   Once you start putting up anything under the rafters you need to change the design. I'm sheeting the roof with osb and putting down ice & watershield. I will be using fasteners that have a rubber? washer under them but even they can leak so the ice and water shield seals around the fasteners below the panels. The steel roof really is there to protect the ice and water shield.

   How exactly are the panels fastened? Is there a way to have air circulate under the steel? Like a rafter chute?

    

2. 
   woody1777 | Jan 10, 2008 03:59am | #2

    As long as you prevent warm, inside air from reaching the underside of the cooler metal roofing panel, you should not have any condensation issues. If you insulate it and install a vapor barrier of some kind then you should be fine.

   Naive but refreshing !

1. 
   CapnMac | Jan 10, 2008 05:41pm | #12

   long as you prevent warm, inside air from reaching the underside of the cooler metal roofing panel

   Just outside Montogmery, AL?  All the air is warm, moist, and damp--about 225, 250 days per year <g>.

   Short of reroofing, this might be a good place for rigid foam between the rafters, and a paperless wallboard for the ceiling.  But, I live in a similar hot, humid lattitude, so that may bias my thinking.Occupational hazard of my occupation not being around (sorry Bubba)

3. 
   Piffin | Jan 10, 2008 04:09am | #3

   insulate well and use a VB on the warm side. seal all penetrations.

   You surte the roof is nailed on? That went teh way of the dinosaurs long time ago. We use screws with neoprene washers now

    

    

   Welcome to the
   Taunton University of Knowledge FHB Campus at Breaktime.
    where ...
   Excellence is its own reward!

1. 
   DaveRicheson | Jan 10, 2008 02:22pm | #8

   That went teh way of the dinosaurs long time ago. We use screws with neoprene washers now

   We still have a few of them lurking around here. At least one of the pole barn guys around here offers a lower price if he uses nails.

   I may be wrong, but wasn't the rule; nails on the ribs and screws in the flats?

   The last nail on roof I did was galv. corragated and was nailed on the high part of the wave. That has been at least 16 years ago.

    

   Dave

1. 
   Piffin | Jan 10, 2008 02:29pm | #9

   That is right for the old corrugated. The flat pan modern styles need screws with washers in the flats. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   NEXTLEVEL | Jan 10, 2008 02:48pm | #10

   Let me clarify this situation.  The metal is 3' wide painted steel panels and they are screwed on.  The slope is about 2/12.  The rafters have 2x4's nailed on top of them for the metal.  The rafters are 2x8.  Then there are 2x8 ceiling joists that run flat, not with the slope. 

   Of course the joists and rafters meet on the outside wall and I have about 30" attic space against the house where everything joins.  So I do have some space between the insulation and the metal.

   I can vent the soffit but should I also cut in some roof vents for air circulation?

   James Hart

1. 
   Piffin | Jan 10, 2008 03:25pm | #11

   Insulate and VB at ceiling level then.Whether to let in roof vents depends on how the roof was capped at top of this shed roof. It might be gasketed or might be open at top so it can vent already.I am one who believes not every roof needs to be vented when you can insulate well enough and totally control air infiltration at penetrations and use good VB. If no moisture can get to the cold metal, there will be no condensation.one problem you have is that this was done barn style. if it vents, there is a possibility of drawing damp exterior air into the space and having it condense on cold metal and cause drips even tho no moisture is getting to it from inside the house. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

4. 
   dirtyturk | Jan 10, 2008 04:24am | #4

   Nextlevel, there are a number of solutions to your question. But a couple of questions and assumptions first.  You say its nailed onto the 2x4s...is this roof a agricultural type of steel roof? (The panels would be about 3foot wide and continuous and installed with an overlap). Galvanized or painted? If, as you say, the system is nailed in that may be the source of some future problems, the owner's not yours. Any movement will, repeat will, over time start rust or movement at these.

   And I answered my own question. If you can see the nails then the system is not a standing seam roof...all the fasteners of a SS roof system are concealed.

   (Current attachment method is neoprene washers under a screw. Effectively self sealing.)

   The key to the whole thing will be in the effectiveness of the ventilation under that steel. The steel is much more reactive to sunlight heat buildup and with a little stagnant moisture in the space you will get the 'sweating cold water pipe' thing. Is there a half ridge vent at the main part of the building? A couple of mushroom vents?  I had the problem with a shed roof over the kitchen....really bad moisture buildup. I had to cut in vents at the top and put in eave venting (which never existed either) but it solved the problem.  I would install the insulation carefully so as not to allow any more potential moisture up into the void between the ceiling and the steel. That space must be kept dry as possible. I think putting plastic over the insulation only contains the moisture. 'course we aren't talking about a huge moisture buildup either. Most attic insulation batt I've installed was unfaced.

   Hope I made some sense.

   ciao, ted

5. 
   user-246028 | Jan 10, 2008 05:37am | #5

   If there is any doubt, use a j-mould on the edge of the drywall that will make contact with the steel. That should take care of any condensation problems.

1. 
   Tyr | Jan 10, 2008 09:33am | #6

   To be clear. You have rafters of an unknown dimension (but hopefully greater than 2X4)and then what would amount to purlins,(measuring 2X4) fastened to the rafters? And this is human occupied space? PolyIso not in the picture? Tyr

   Edited 1/10/2008 1:35 am by Tyr

2. 
   Piffin | Jan 10, 2008 01:37pm | #7

   There is no contact between steel and SR in what he describes. The SR is a ceiling on a plane parrallell to the roof, but on the bottom of the rafters, while the steel is on top of them 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!