# Interesting condensation effect



## MASSDRIVER (Feb 12, 2014)

Roofer forgot to use short nails on this small eave section so I'm cutting them flush. Foggy today. Thought the roof was leaking at first.

Every nail has its own little drop
	

	
	
		
		

		
			





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## steveray (Feb 12, 2014)

Most of ours are covered in ice about now......


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## mjesse (Feb 12, 2014)

Yep, here we get frost balls.The nails in the attic frost up too  

View attachment 1003


View attachment 1003


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## conarb (Feb 12, 2014)

Now you see why these unventilated attics are rotting out, particularly those with spray foam.  I had an inspector tell me that they allowed it in two homes, it's "raining inside those homes now".


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## MASSDRIVER (Feb 12, 2014)

conarb said:
			
		

> Now you see why these unventilated attics are rotting out, particularly those with spray foam.  I had an inspector tell me that they allowed it in two homes, it's "raining inside those homes now".


I remember heated discussions years ago on The Old Badger Pond and the Fine Homebuilding board.

Heard some good theories, and there were stories of practical application of sealed spaces.

I didn't know enough to get involved, but I have seen a couple of saturated area that were not vented properly.

Brent


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## jwilly3879 (Feb 12, 2014)

In my contracting business I was called to see why a metal roof had blown off one side of a house. The roof sheathing had rotted around every screw. The roofing contractor used 2" screws through 5/8" sheathing. I had pictures of the icicles hanging from the screws for the homeowner to show the insurance company.


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## steveray (Feb 12, 2014)

Should the metal roofing just be fastened to the sheathing?



			
				jwilly3879 said:
			
		

> In my contracting business I was called to see why a metal roof had blown off one side of a house. The roof sheathing had rotted around every screw. The roofing contractor used 2" screws through 5/8" sheathing. I had pictures of the icicles hanging from the screws for the homeowner to show the insurance company.


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## mtlogcabin (Feb 13, 2014)

R905.2.5 Fasteners.

Fasteners for asphalt shingles shall be galvanized steel, stainless steel, aluminum or copper roofing nails, minimum 12 gage [0.105 inch (3 mm)] shank with a minimum 3/8-inch (10 mm) diameter head, ASTM F 1667, of a length to penetrate through the roofing materials and a minimum of 3/4 inch (19 mm) into the roof sheathing. Where the roof sheathing is less than 3/4 inch (19 mm) thick, the fasteners shall penetrate through the sheathing. Fasteners shall comply with ASTM F 1667.

R905.3.6 Fasteners.

Nails shall be corrosion resistant and not less than 11 gage, 5/16-inch (11 mm) head, and of sufficient length to penetrate the deck a minimum of 3/4 inch (19 mm) or through the thickness of the deck, whichever is less.

Code change? Anybody want to propose requiring  a minimum 3/4" sheathing in cold climates?


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## mtlogcabin (Feb 13, 2014)

conarb said:
			
		

> Now you see why these unventilated attics are rotting out, particularly those with spray foam.  I had an inspector tell me that they allowed it in two homes, it's "raining inside those homes now".


Agree no ridge vent it is just trapping moisture

Old timers around here don't like putting vapor barriers on ceilings. Claim it traps moisture in the ceiling gypsum and causes mold.


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## MASSDRIVER (Feb 13, 2014)

steveray said:
			
		

> Should the metal roofing just be fastened to the sheathing?


That's common. If you want otherwise you have to install cross blocking at say 24" intervals. Framers look at you funny when you say that.

Brent


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## ICE (Feb 13, 2014)

> Code change? Anybody want to propose requiring  a minimum 3/4" sheathing in cold climates?


Only at an exposed overhang.


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