New metal roof without sheathing?


#1

HI. this past fall, I had a new standing seam metal roof put on an old house that used to have metal shingles. The old decking is just 1/4" boards (I think) that are spaced several inches apart. Unfortuantely, with the new roof, the wind noise is just terrible. IT keeps us up at night-- sounds like there are people in our attic flapping around sheets of metal. I have 2 questions.

1: Is this the normal way to go about putting on a new metal roof? Should the contractor have at least asked us if we wanted to put up new plywood sheathing?

2: Is there anything that I can do at this point to stop the noise? Any insulation products that can be put on the underside of the roof inside the attic to dull the noise?

Any help would be much appreciated !


#2

This is a tricky area & you will probably get responses akin to if you had asked “what’s yoru favorite color”?

Essentially, it’s a cost factor. If you had received a quote from someone & all other areas were similar (standing seam, thickness, etc) but the $$ was way off then chances are it was in the decking. If it was MY house, I’d sheath it & lay something like a Titanium UDL or TriFlex 30 on the decking prior to the metal… but that’s me.

You can get various types of insulation & nail or staple it to the truss system & purlins; 4’x8’ sheets of wall type insulation might be my suggestion (& will assist in energy efficiency as well as sound deadening).

Let us know what you decide to to; we’re a nosy lot around here.


#3

Well aside from tearing the roof off and putting the proper substraight in not a thing i can think off. Whom ever did it IMO should have decked the job before installing the standing seam.


#4

Hi,

I find it hard to believe that these two roofs were nailed to 1/4" purlins.

I would have installed over the purlins usually 3/4" - 1" thick. The noise should have been the same as the last metal roof.

To eliminate the noise, find a insulation contractor that sprays foam insulation. Spray it to the underside of the roof and between the rafters this will stop the noise and should help to secure the metal.


#5

Thanks for all the info! As I mentioned in my post, I really don’t know what size the decking boards are, so they may in fact be bigger than 1/4", I’ll check on this. And, the reason the previous roof didn’t make any noise was because it was metal shingle-- the pieces are too small and sturdy to cause much noise from wind. I wouldn’t have replaced it if it hadn’t absolutely been falling apart. This house is old. Previous roof was probably put on sometime between 1900 and 1920. Can someone explain to me what a purlin is? I initially thought that it was just another word for decking, but I think I’m missing something here.

If I had known then what I know now, I would have insisted on new sheathing and better substrate (even if it significantly increased the cost), but my roofing contractor didn’t even mention these options when I had the roof put on. Now I’m kicking myself for not being more involved. Anyway, thanks for your suggestions and keep them coming. I was hoping that we might be able to spray on foam insulation-- any more thoughts on that?


#6

read lefty’s post right above your last one. i also agree with the spray foam insulation.


#7

Looks like it’s time to start up a metal roof repair company.

Your old decking was probably 3/4" 1x4 boards.

I like the idea of spray insulation on the underside of the deck. But, if you have a bad installation and the roof starts to leak, I think the decking and rafters will rot before you know it’s leaking.

JMO


#8

http://dictionary.reference.com/browse/Purlin

Your rafters support / hold up the sheet rock that is the ceiling.

Trusses are the angled beams that hold up the roof deck.

Purlins are horizontal slats of wood that (in this case) support the metal roof components. You will also see these in a cedar roof as the part that is nailed into to hold the top portion of the cedar shakes.

Sometimes this purlin is called a lathe.

I do like the idea of a spray foam option. Anything that can add to the insulation is a benefit as well.