Metal Shed Roof is Bad Idea

I am replacing the metal roof on my shed because it rains condensation every night. My first year with it molded the center of a 6 cord stack. The shed is empty at the moment so it’s a good time to do it. I recommend never using metal roofing on a wood shed. It’s cheap and easy but not effective for keeping wood dry. I am in western Washington.

 

I haven't had that problem, but, I live in a less humid climate.

 

Weird... lots of metal roofed structures around here. I would guess poor ventilation more of a concern.

 

That's odd. How close was the roof to the wood stack? Also what where the dimensions of the stack? Was it a square or longer? I ask because lack of airflow might be the problem.

 

I can see a situation with lots of green wood drying under the metal roof; the warm moist air raising from the stacks hits the cold metal roof and condensing and dripping back to the wood that one is trying to dry. Maybe a higher pitch would help the condensed moisture to run to the edge and drip off. So what are you going to replace it with? You would probably have the same problem with the plastic or fibreglass roof panels.

 

The pictures of the shed show it empty, wide open and still dripping. The could be no ventilation issue at this time.

Western Washington is a very mild climate. We sit at and above freezing all winter here. It does not rain condensation when frozen. Ideally a shake roof, but wood deck comp shingle is what it needs.

Wood deck and asphalt shingle.

 

The shed is just a roof. I don’t think it’s an airflow problem. It is two 12’ x 12’ bays with a 1:6 pitch.

 

it will still condensate, the wood will just absorb the moisture more until it can't and will mold/rot.
This is why there are vents in roofs, ridge cap/gable vents and those square vents I can't think of the name right now.
I'm not sure how you could cut the condensation down on that though, it's open all the way around.
Is it in the shade all the time? no wind getting to it?

 

Wow, interesting. I put up my first metal rood shed this spring, filled it w. 15 cords of wood and have nothing but phenomenal things to say about it. It is wide open though, no sides.
I would think climate must make all the difference.

 

It is west facing, open to prevailing breeze. Full sun from noon on.

 

It must be. Everyone that loves them is in the northeast. I could then say that metal roof wood sheds are not so good in the western Washington climate.

 

My neighbor built a greenhouse that looks like a perfect wood shed, storage/kiln setup. All clear corrugated poly panels from Menards. Cheap. Stays Africa hot inside whenever there is a hint of sun. I'll be trying these. I've never seen any condensation inside his structure. May be worth a thought.

 

I'd be half tempted to put a weather station in it to log humidity and wind speed to see what is going on.
My tarps get condensation on them too. Which I blame on the ground being damp and the sides of the tarp being too low to let enough air thru.
I am now trying a double pallet situation where I stack 2 pallets and than stack wood on top to see if that allows more air thru the bottom.

 

Interesting...
Like said above, climate has a lot to do with it. My pole barn sweats when the temps swing, but not to where there’s water dripping.
What fasteners did you use? Screws w neoprene washers? No purlins?

 

I like the way you're thinking but I'm not going to go all psychrometric on my wood shed.

 

Regardless of roof covering, make sure you have good ventilation. Ive seen what that can do on residential structures in attics from many years of roofing.

 

Less mass and temp differential by using lath boards would probably work.
I don't think the problem there is the metal roofing.

 

The odd chance it snows, I don't know if lathe board can support any kind of load. Agree on the metal not being the problem though.
I did some modular homes with 1x3's for rafters, they couldn't support my weight when I was just bones and clothes.
Snapped one right in half and ended up in their bedroom.. oops..

 

I would think the metal would be fine if you sheathed the roof first with cdx plywood. Put down a layer of 30lb felt, Tyvek or Ice and Water Shield and metal on top. This would keep a barrier between the cold underside of the metal and the water vapor from the wood. Would still have to insure ventilation by having open relatively open sides and leave some space between the stack and the structural beams.