Rib metel roofing

[moodnacreek]

Unvented, no air flow probably.

Sheds, barns unheated buildings during certain weather changes will do this. I think solid sheathing under the tin will stop the drips. You don't always have the natural air flow to beat the condensation.

[Don P]

Or tarpaper over the purlins under the tin. With dirt floors it is usually much worse, the damp ground gives up moisture and the metal is below dewpoint. For an experiment you can put plastic down over the dirt to see if that is the source. The other source is humid outside air hitting the below dewpoint metal. A lot of people vent their metal roofs but again that is one of the folk wisdom kind of things. As per most manufacturer's directions I put metal on  over a solid papered deck and seal the ends to keep outside air from getting under the cold metal. With all of this read the directions then decide but do bear in mind those directions come from more experience than most of us have. I work on stuff that belongs to others so unless the owner makes a specific call it takes some pretty compelling arguments for me to go against the company instructions.

[Tom King]

Boathouses here with open purlins, rain most mornings.

I have put 1/4" plywood over 2x4 purlins, to hold synthetic roof paper, and that worked fine to stop the condensation rain.

[Skip]

When the Amish built my garage they used 'double bubble ' under  tin, no rain forest ,adds bit of insulation . Used it on my open front equip. sheds, no more wet butt in the mornings when I get on the tractors.   No signs of any trouble been 10 yrs .

[SwampDonkey]

Unvented, no air flow probably.

Sheds, barns unheated buildings during certain weather changes will do this. I think solid sheathing under the tin will stop the drips. You don't always have the natural air flow to beat the condensation.

The garage here is unheated, it is sheathed and vented, no water on the floor. No rust on metal. Since I was never going to heat it, I wasn't wasting insulation. Insulation would just trap water from the air in high humidity and dry rot the place. As it is, it is bone dry and breaths. Seen unheated, insulated garages sweat in temperature swings.

[mike_belben]

Hard to read the directions on used tin.   ;D



The stuff im talking about now isnt much more than a hay roof thatll get sorta walled in and maybe have a barrel stove to warm up near when im working, but no expectation of warming the space daily, its just a work shed.   Floor is gravel now but will be poured in time.  Doing my best to transport all roof runoff far and away. 


Cant really justify a plywood layer when allocating the funds i dont have so these are just rafters with purlins then tin.  The tin came off one chicken barn and onto another except im the chicken. 


I guess ill oil one side of a movers blanket to put over the lathe and bridgeport when i get them down and just let it rain.  Once the sun hit the drops flash right off.  

[moodnacreek]

Hard to read the directions on used tin.   ;D



The stuff im talking about now isnt much more than a hay roof thatll get sorta walled in and maybe have a barrel stove to warm up near when im working, but no expectation of warming the space daily, its just a work shed.   Floor is gravel now but will be poured in time.  Doing my best to transport all roof runoff far and away.


Cant really justify a plywood layer when allocating the funds i dont have so these are just rafters with purlins then tin.  The tin came off one chicken barn and onto another except im the chicken.


I guess ill oil one side of a movers blanket to put over the lathe and bridgeport when i get them down and just let it rain.  Once the sun hit the drops flash right off.  

Plywood? I thought you had a sawmill!

[mike_belben]

Its a chainsaw mill so ill be as old as you by the time i make that much plank! 

:laugh:

[Larry]

Whether you get condensation and how much is location dependent.  When I lived in north Missouri, the only time condensation was much of a problem was in the early spring.  Rest of the year the machine sheds were usually fine.

I found tar paper laid over the purlins before putting on the tin solves the problem just fine.

Eighteen years ago when I built my Arkansas shop I found a product that I think is better.  It is Dow Blue Cor which is a styrofoam fan fold insulation.  Its only about a 1/4" thick and doesn't have much insulation value but it sure helps to keep the shed cooler in the summer.  It wasn't very expensive but that was 18 years ago. Its the blue stuff in my picture.  I added a ceiling in the shop later on.



Only drawback is if a hummingbird comes in it thinks the blue roof is the open sky.  Makes em really hard to catch.

[Don P]

Doesn't seem to matter if the ceiling is wood, those things will not come down to exit, they stay up there till they fall. We had one that we had opened everything hoping he would come down and leave. He was so pooped I set up a stepladder, climbed up and just plucked him out of the air, that is a tired hummingbird  :D. Fed him some coke, the only sugar water I had, and he revived after a few minutes and took off.

[SwampDonkey]

Analyzing.... Now make lumber. :D

Squaring up - YouTube

Lap siding, with the Alaskan Chainsaw Mill - YouTube

[moodnacreek]

Its a chainsaw mill so ill be as old as you by the time i make that much plank!

:laugh:

I told you where the sawmills where down there.

[rjwoelk]

On our log cabin roof we did the following.
Sheeted the roof.
Used water shield  membrane on top
1 inch strapping. 
Steel roofing.
Underside of the roof/ warm attic was spray foamed 4 inch .