I posted a question last week or so about my neighbor's roof having a
wet spot on it. Two days ago, I took a few more pictures. It was below
feezing overnight and at 7:30 am the neighbor's roof looked like this:
What do y'all think?
The main suggestion under the other post were that it is caused by a
possible ventilation problem. The bathroom that is right there where
this spot is.
Thanks so much for everybody's input!
It's hard to tell, but it looks like the "spot" is frozen. If so
perhaps it's just frost? Maybe that section of the roof is getting
*better* air flow so it's staying cold longer. Frost on roofs
around here is a good sign. ...well not this week (record temps).
Ya, but why would just that spot 'frost' and not the rest of the roof? I
doubt the rest of the roof is 'bad' and this one spot with frost is 'good'.
Obviously, there is a problem with moisture at that point on the roof.
Excess moisture in that spot is causing the frost. In the last round of
pics that were posted, it looked like the sheathing was sagging and damaged
as well. Could be caused by problems with venting. You really need to have
a pro look at this. One who can investigate the cause, and correct it.
There could be a boatload of mold up there as well.
The problem will not fix itself or go away, but it will get worse!
Are you sure that the entire roof isn't frosting during the night and as soon as
the sun comes up it all melts except for that spot? Perhaps that spot has
better insulation. Does the house have cathedral ceilings (no attic)? That
would typically not be the case in bathrooms so they would still have a space
I'm going to go out on a limb here, and say that's perfectly normal. The frost
shows which parts of the space under the roof are properly insulated: every
place you see frost, the insulation is good. Where you don't see frost, the
insulation is inadequate: so much heat is escaping from the house in those
places that the roof is too warm to collect frost.
In a nutshell, the parts with the frost are OK. It's all the parts that
*don't* have frost that have a problem.
That's my guess, anyway.
Doug Miller (alphageek at milmac dot com)
Frost is moisture from the air which condenses on objects which radiate heat
to become colder than the surrounding air. The eaves are exposed to the air
on both sides and stay warmer than a well insulated area which is exposed on
only one side.
Frost forms when a surface cools to a temperature which is colder than
the dewpoint of the air next to the surface. The frosted area of the
roof must be cooler than the rest of the roof and has nothing to do
with moisture in the roof itself.
That does make sense, but why are the shingles wet when it's not below
freezing? That's why I was thinking that it's this wetness that causes
You all have some very interesting theories! My neighbor hasn't called
anybody yet to look at her house because of the holidays, but I hope
she will soon. She already had a leak in her roof in another spot last
year. She usually calls the guy who built the house, but I would think
this is not a good idea. If anything was in fact wrong with the
construction of the house, he sure wouldn't admit to it and fix it, he
would try to cover it up instead.
Glad it ain't my house!
Because condensation can occur above the freezing
point; look for dew on the grass every morning.
What you are seeing is a natural phenomenon that
occurs when there is nothing wrong with a roof.
I assume you are real, but you sound like a troll.
Next you will think something is wrong if snow
melts off the roof on the south side but stays on
the north side.
The frost/snow is where it is the coldest. In
other words, all of the roof is colder than the
are where the frost is. The area where the frost
is either the area of best insulation or most
ventilation. Your neighbor should wish that all
of his roof look like what you call wet spots.
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