Ted Stephens
1/8/2014
I am thinking about putting a metal roof on a double wide. One roofer tells me he can lay plywood over the old shingles and metal over that. Another roofer says he will remove the shingles then put down the metal. Removing the shingles cost more. Any problems with leaving the shingles? Thanks Much
Todd Miller
Classic Products, Inc.
1/8/2014
First of all, make sure that your roof has adequate pitch for whatever metal roof he's installing. I like the idea of another later of decking as it will help avoid transferring cold and possibly creating condensation issues. Has anyone discussed putting the metal on battens to create an airgap or possibly even venting the airgap. My one concern with adding decking is weightload. It may be wise to contact the home manufacturer and see what they can tell you as far as the weight the home can handle.
Ted Stephens
1/9/2014
The roof pitch is 2/12. I think they both are talking about Ag metal roof. No battens were mentioned by either roofer. The home has 10 square vents across the roof now. The roofer that wants to remove the shingles said he will reuse the vents. The other said he will install ridge vent. As far as I know Fleetwood is out of business so I don't know how I would check weight load.
Todd Miller
Classic Products, Inc.
1/9/2014
Thanks. I will reiterate my caution on roof pitch and making sure the product you use is appropriate. I have seen a few jobs over the years where there was very limited effective ventilation and insulation. And, when the metal roof was installed, it's contact with the roof deck dropped the temperature of the roof deck just enough that it became the straw that broke the camel's back and created condensation on the underside of the decking even though this had never before been an issue. This is my concern for you. Even though there are roof vents, they may or may not be doing anything. Having the metal on battens and/or over the old shingles will help prevent this issue of dropping the roof deck temperature in a way that leads to condensation.
Ted Stephens
1/9/2014
Thanks. So you are saying the layer of plywood over the old shingles would be a good thing and adding battens would be even better? " If weight load is ok" One more question and I will leave you alone. Should the battens go under the plywood or above and under the metal. That may be a dumb question but I'm just trying to understand so I can sound like I know what I'm talking about when I talk to my roofer.
Todd Miller
Classic Products, Inc.
1/9/2014
Yes, anything you can do that adds a thermal break (air gap) or R Value (thermal mass including insulation) will help avoid the scenario I described. Not all metal roofs can be installed on battens. The location of the battens is really not a huge issue ... Now, this makes things more complex but for maximum energy efficiency (keeping heat out of the home in summer) cross battening would have the greatest effect. This consists of vertical battens followed by either horizontal battens (or decking actually) and then venting the resulting vertically oriented air chambers.
Ted Stephens
2/21/2014
I have a nice new metal roof. But, Now that it's on I started to think " Should have done that first". It's a doublewide with cathedral ceilings. The roofer put in a ridge vent. Before it had 8 or 10 square vents near the ridge and vents under the eve. I can't get in my mind how a ridge vent would work. Is the space between the rafters not closed off by the ridge beam, On both sides? And, mostly full of insulation? I don't think he cut any openings in the decking to allow air flow. I called the roofer to come back and explain it to me but I would like to have any info I can before he gets here. It's a year 2000 mobile home. All the decking look good when he tore off the old shingles so the old vents should have worked, I think. Thanks
Todd Miller
Classic Products, Inc.
2/22/2014
Ted, for a ridge vent to function, the roof deck is cut open for about a 3" width at the ridge. A great source of venting information is available for homeowners at www.airvent.com
Ted Stephens
2/24/2014
I called the roofer back out Saturday and we went over my roof. This is what I pointed out that I did not think was right. 1. No over hang. There is a metal lip of about half inch all along the edge that was installed with the old roof. In my mind the new metal should over hang this one inch or so. In most places it does not even come to the edge of this. 2. There is no closure strips in the ribs. I told the roofer that if he put the closure strips in I may let the over hang go. But I'm having second thoughts. Should I let it go? 3. I have a large metal stack on the fire place that was put there when the house was built 14 years ago. It near 18 inches in dia at the base. It goes from touching one rib, The next rib hits dead center and the third rib had to be cut to get it to fit. So it blocks two channels from draining. Rain just sits behind the stack and can't run off. He put a bead of silicone caulk to seal the stack. Seems to me that water should not stand on a roof at any penetration like that. Silicone used as a sealer on a roof? 4. The ridge vent. The old roof had 8 or 10 box like vents. He removed them and said he put in a ridge vent. When I looked at it I found he did not cut the decking back to allow air to escape. Really all he had on the ridge was flashing in my mind. I told him I could not except that and he said he would cut the deck back. He was going to cut it back and just put the flashing back. But, What about insects, Wind and rain blowing back under? Later he said he would put in a material to allow venting and keep out insects. Is that the correct way? 5. The roof makes a lot of noise during the day, Not from rain. I think it's caused by the sun heating the metal and expansion. Is that normal ? Thanks for your time and any advice you can give. Ted
Todd Miller
Classic Products, Inc.
2/24/2014
Ted, there are all good questions. To help out, do you have any photos you could email to me please? [email protected]
Ted Stephens
2/24/2014
I sent the pictures. I did not send pics of vent because I would have to remove the flashing. Thanks
Todd Miller
Classic Products, Inc.
2/24/2014
Got them. Thanks! Will email direct to you.
Rob Willey
9/26/2014
Homeowners often ask us whether a metal roof is right for their home. Fact is, metal roofs can be a great addition to just about any home. The key considerations in making a decision, though, are what the homeowner’s goals are with a new roof and also what special considerations there may be with their roof.

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