Condensation on Metal Roof

[Sweetrun]

Installing a new tin roof over 1x3s 12 inches on center. The roof pitch is 9 over 12. The sugar house is 14x16 with a 2x6 evap and a cupola. Worried about the possibility of condensation/rain in side. Anyone have any thoughts? Thanks!

[tuckermtn]

how big is your cupola? see previous posts on cupola sizing...but general rule of thumb is equal to size of your evaporator...

We sized our cupola for the 2 x 6 we started with...was fine for 25 gph. then we put in a 2.5 x 8. 50 gph. you can see where this is headed...

we have alum. roof on 1x3, 12" on center. gets pretty wet in there...wound up putting rigid insulation in the main bays between the rafters..helps some...also have pvc pipe cut in half to serve as gutters (pitched to the side) hanging over the pans to catch the drips coming off the rafters...

I think it was Amber Gold who was putting chip board under his metal roof?

[WESTVIRGINIAMAPLER]

I have a full hood on my 2x8 but the front part of the hood is suspended above the syrup pan several inches, so I do get some steam leakage around the front pan. I don't have any condensation problems unless it is raining or snow on the roof as I have a metal roof similar to what you have. Since I don't have a coupla, it can get 80+ degrees in the sugarhouse when I am boiling and this is a 24 x 48 building with no insulation and only a 2x8 evaporator. All the heat in the building pretty much takes care of any moisture problems unless there is rain or snow. That is one of the disadvantages of a coupla is that it does let out a lot of heat and cools the building a lot.

[Russell Lampron]

I have a metal roof on 1x4's spaced 2 feet apart and the first season I got dripped on alot. I put a steam hood on the flue pan and problem solved.

[Sweetrun]

The cupola is 8 feet long, so there should be enough area. I guess one option, in lieu of a steam hood, would be to completely strap the roof in 1x instead of 12 inches o.c. Might work?

[Lwood]

My sugar house is 12 X 16, galvanized steel roof with the 1x3's 12 inches on center. When I built it it was for a 2.5 x5 homemade rig. I knew that I was going to have a condensation issue. So my soultion, while not perfect, has worked quite well. I took some 1x3's and made a frame that fits the bottom of the coupula and and extends down to about a foot above the pans. The ends go straight down from the roof, But the sides taper out slightly. Lined the inside with plastic. Works great, only get any drips when the wind is blowing hard. It is still in place even now with the 20x66 that is there now. However I am adding a hood and preheater this year so will be removing it.

[3% Solution]

Sweetrun,
I'd buy some 7/16 OSB at Home Depot for $7.?? something a sheet rather than strap the whole roof.
Put 15 lb. felt on the plywood, then your metal.
No leaks, no drips. got a roof that will last for many, many years!
How wide are your rafters apart?

Dave

[halfast tapper]

Sweetrun,
I would do what 3% said. You"ll have a good no drip roof then. You could also build a tunnel to your cupola with plastic sheeting. Then all your steam is going up the tunnnel and not against your roof. But then you have to cut drain pipe in half and nail it to the bottom of the tunnel frame work so the condensation drips in the drain pipe and not back into your pans or all over your rig and floor.
I definately would go 3% way. Alot easier and nicer.

[royalmaple]

I boarded my entire roof with 1x pine boards left over from the construction of the sugarhouse. Then I put went over the boards with ice and water shield, then screwed down the metal roofing. I get very very little dripping. Most anything that drips just runs down a rafter and drips at the edge of the wall. Best thing you can do is to not have exposed metal roofing to steam. Little more work and a bit more money but you'll have a much more solid building and way less dripping.

[paul]

I agree with matt, we boarded the inside of the roof with 1x pine looks good and no drips.

[gmcooper]

The ridgid insulation works well especially as a repair if your roof is done.
We used 1" styrofoam but the 1" foil covered might work a tad better. The added insulation will keep in a fair amount of heat if that is an issue.
Mark

[Haynes Forest Products]

Keep in mind that you my want to walk on the roof so make it strong with OSB

[maple flats]

I have 1x6 at 12" on center and got a lot of dripping the first year. Then I made a hood, covers all of the flue pan and is above the syrup pan about 18" and covers 20" on a 2' pan. I get no dripping now. My hood has 2 10" steam stacks.

[Sweetrun]

The roof tin is not on yet, so I think I will go with the complete 1x underlayment with no metal exposed. Thanks for the input folks!

[Amber Gold]

I agree with tuckermtn. I have rafters 16" o.c. and went with 1/2" OSB. Plenty strong enough and I think it was $9 per sheet at the local lumber yard. I also put 15# felt between the metal and OSB. This is a cheap, effective, and quick method to sheath a roof.

[Yorkholomaple]

We nailed rough cut 1 by 12s to the rafters then put felt down then the metal and i have never had one drip!

[Buckeye mapler]

is this the same felt used under shingles? i too have a metal roof and would not want to learn the hard way about condensation.

[peacemaker]

yes same felt
if u had lots of money to spend u could ice and water the whole deck then screwed the tin down

[Haynes Forest Products]

If you overlap the tin and use the recemended rubber washer screws why the tar paper

[peacemaker]

between the tin and wood will condesate as well this way your wood is protected

[royalmaple]

Peacemaker gets an "A" for the day.

[peacemaker]

yippie do i get a smiley face sticker in the corner of my paper to take home to my mom

[Russell Lampron]

Yes you get a smiley face too.

[peacemaker]

yeah mom will be so proud .... never got A's in school except shop class and since my shop was nicer then the schools figured that was like cheating

[WESTVIRGINIAMAPLER]

My baked enamel roof is white on the underside and looks nice, I would rather get a few drips every once in a while as to look at black felt.

[Haynes Forest Products]

There is no reason to put felt down if your putting tin over firing strips. Hell I wouldnt put felt down over OSB.

[dano2840]

what im going to do once we get the roof on is put wide 1x on top of the rafters and then put down tar paper on top of that and then put the tin roof on that

[Haynes Forest Products]

WHY? A metal roof that is properly overlaped and screwed down with rubber washer screws will not leak unless it is layed flat.

[peacemaker]

haynes its not that it will leak it will condensate between the tin an wood thats what you are ptotecting from and brandon u wouldint see the felt

[tuckermtn]

I spent 3-4 hrs today taking the metal roof off, pulling the straping off, and then replacing it with 1x8 shiplap pine 2nds from the local pine mill. Only did the area right around the evap where the most moisture is.

I did not do the felt on top of the pine boards. My feeling is that with the wood on the inside, facing the steam, the steam won't linger long enough to condense on the underside of the metal roof...but we'll see in a few months...

-tuckermtn

[WESTVIRGINIAMAPLER]

I have 1x6 rough cut pine boards on 12 or 16 inch centers, I am not sure. What I was saying is that I can see a lot of white on the underside of the baked enamel roofing I have and I would hate to have to look at ugly felt. Metal roof does sweat and I would think if you did have solid sheeting like plywood or osb underneath it, felt would cause problems down the road due to it making it difficult for moisture to escape that gets trapped between the felt and the metal roof. I may be wrong, but I see rust problems on the underside of the metal roof down the road or am I overthinking this??

[Haynes Forest Products]

I think its over kill If you dont close up the ends top and bottom with the foam it will breath and the moisture will disipate. Come summer time the sun on that roof will cook all the moisture out.