I was up in my attic this morning and noticed little bits of ice lying
around---small balls, perhaps 1/4" in diameter. What seems to be
happening is that water is dripping from the roofing nails, then
freezing into the little ice balls. Only some of the nails are wet;
most are dry. I would guess that that makes it more likely that the
moisture is coming from the outside rather than from condensation from
air from inside the house. Is my logic right? Is this normal, or
should I take measures to repair?
Thanks in advance!!
Ben: It sounds as though your attic is not ventilated correctly?
Assuming your house is has insulated ceilings with an appropriate and
sealed vapour barrier on the warm side of the insulation ?
The condition could be serious and cause rot/mould.
Normally what is happening is that warm and therefore moist air from
the house, some of which will inevitably leak into the attic is
condensing on the cold nail tips.
The requirement here, for example, is that there be venting of 0.3% of
the floor area and that it be cross ventilation.
That means that for each 1000 square feeta of area there be a minimum
of 3 square feet of ventilation (not all in one place) but spread
around as soffit vents, vents in the eaves or even roof vents.
If you have insulated ceilings make sure the insulation does not get
wet from such drips. Wet insulation is not only useless it can cause
rot and bad ceilings.
I also think it is ventilation related. Make sure that your
insulation is evenly distributed and that you have good air flow thru
the attic. Check around the chimney for gaps in the insulation. Heat
from the heater room will sometimes cause condensation if it can work
its way into the attic. Think about a ridge vent if possible.
Small note on the "square feet of ventilation." I believe that figure is the
unrestricted area of the ventilation port. If the ventilation ports are
screened, you should take the blockage of the screening material into
account. The finer the screen - say the same material used on a window
screen - the less open space available for ventilation.
So, then: If you have window screen type coverings, I'd double the minimum
size requirement. If using chicken wire, you could probably forget about a
If you get bogged down in the calculations, you can remember the fall-back
rule: You can't have too much soffit ventilation.
If its unheated and vented, then underventing, lack of insulation, or
warm air infiltration is making the attic to warm. The attic should be
near outside temp. Insulating to code is only a minimum requirement,
it is completely outdated. Sealing air leaks can be hard, is there a
full vapor barrier. Condensation leads to mold then rot, then a big
These nails that are dripping, since you did not mention anything I assume
the wood immediately around the nail is sound? Not wet, soft, dry rotted,
etc like it was just about new? Use the likes of an icepick to poke at it.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.