# Rusty nails



## Ed the Roofer (Jan 27, 2007)

Its mostly trapped humidity from not being properly vented probably, but the ice damming is a possibility too.

When the internal humidity level reaches a high enough saturation point and begins to collect on the underside of the deck sheathing, it will begin to travel down the slope of the roof on the under side.

Look at some of the rafters towards the bottom of the slope and you will usually see sign of staining or degradation near the exterior wall.

That definitely is minor water leak damage by the pipe, either from an actual leak from the boot flashing or fron the pipe having condensation buld up from the internal sewer gasses being warmer than some of the exterior colder temperatures.

That is why I wrote on another thread about not caulking the bottom flange of the pipe boot flashing, so that you leave an area for the trapped condensation to have a place to exit from under the flashings, ratrher than remain under them to eventually wick into the decking.

Ed


----------



## FatAugie (Aug 2, 2007)

Yeah, I thought so. The nails that are really screwed I figured must be water hitting them at both ends, top and bottom. The majority were just the under side, so hopefully the ventilation I'm adding with the ridge/smart vent/soffit vent panels will yield more than 150:1...in the order of 125:1 or so.


----------



## Ed the Roofer (Jan 27, 2007)

That will improve things substantially.

Ed


----------



## the roofing god (Aug 2, 2007)

that`s water driven under the flashing,and the reason to seal the flashing down,you didn`t check the reference on pipevent flashing I left,you don`t get that kind of heat difference from a plumbing pipevent to cause condensation except the heat flue,and that`s doublewalled to prevent problems(mcgraw hill construction manual)look it up-:whistling2:


----------



## FatAugie (Aug 2, 2007)

Actually, those really rusty ones were from different spots on the roof above, below the flashing (i.e. 3 - 4 feet on either side, not right up next to the flashing). I ended up replacing 5 sheets of sheathing that were screwed with mold. I'll get pictures today and post.

I know the manual you're speaking of, but don't have a copy. I looked online for a copy but didn't see one. Are you suggesting I go to the library?


----------



## the roofing god (Aug 2, 2007)

the reasoning for the rusting nails was right on,the plywood staining wasn`t condensation-google mcgraw hill construction:wink:


----------

