The felt paper _can_ help prevent an ice dam leak on a pitched roof that has
poor ventilation and/or insulation. It's a last line of defense. And the
builders can't always get the roofers or siders on the job as quickly as they'd
like, so they temp it over with asphalt impregnated felt. I like 30 lb. for
roofs, much safer to walk.
>Joe job2 wrote:>What is the logic for using tar
paper behind vinyl siding and under
>ashphalt shingles? Curious. Thanks
>
>
>
>
>
>
>
HUH?
Vapor barrier is designed to keep moisture inside the heated space. It's
vapor barriers _outside_ the studs which foster decay by retaining escaping
moisture and allowing it to condense under the tarpaper. Put your _only_
vapor barrier on the heat side to slow loss and possible capture through
condensation.
And vent your attic to keep condensation under the necessary water shield
from rotting your underlayment.
"Andy Dingley" <[email protected]> wrote in message
news:[email protected]...
> On Tue, 12 Aug 2003 21:46:48 -0400, Joe <[email protected]> wrote:
>
> >What is the logic for using tar paper behind vinyl siding and under
> >ashphalt shingles?
>
> Vapour barrier. The slates / tiles keep the bulk of the water off,
> but it's still going to be damp all around them.
In article <[email protected]>,
[email protected] says...
> "Andy Dingley" <[email protected]> wrote in message
> news:[email protected]...
> > On Tue, 12 Aug 2003 21:46:48 -0400, Joe <[email protected]> wrote:
> >
> > >What is the logic for using tar paper behind vinyl siding and under
> > >ashphalt shingles?
> >
> > Vapour barrier. The slates / tiles keep the bulk of the water off,
> > but it's still going to be damp all around them.
>
> HUH?
>
> Vapor barrier is designed to keep moisture inside the heated space. It's
> vapor barriers _outside_ the studs which foster decay by retaining escaping
> moisture and allowing it to condense under the tarpaper. Put your _only_
> vapor barrier on the heat side to slow loss and possible capture through
> condensation.
>
> And vent your attic to keep condensation under the necessary water shield
> from rotting your underlayment.
>
All depends on the climate you're in. I can't remember off the top of my
head right which way it is, but I think it's in the north you want to
keep moisture in, but in the south you want to keep the moisture out.
But I might be wrong and it's the opposite.
"Andy Dingley" <[email protected]> wrote in message
news:[email protected]...
> If your sarking has to act as a "water shield", then your tiles have
> failed.
Yes, it is quite useful to have a backup when this has occured.
-Jack "Belt and Suspenders" man
On Wed, 13 Aug 2003 18:05:45 GMT, "George"
<[email protected]> wrote:
>Must be different there.
That must come as a shock to someone from Microsoft, but there's still
some diversity in the world.
>Tar paper, in short, is always a water barrier, might be a vapor barrier,
>and if so, should follow rules for vapor barrier installation.
These rules specify the need for a vapour barrier on the warm side of
the insulation. It doesn't forbid having one on the other side, should
this be needed.
If you make the external weatherproofing of small tiles or shingles,
then you use a continous sarking underneath it. This shouldn't ever
need to keep water out (if it does, your roof is broken) but it is
needed to keep the water vapour that will penetrate a normal tiled
roof out of the roofspace.
I admit I know nothing of vinyl siding. It's a heathen practice, but
then most US house-building practices are. I spent a couple of
weekends with your Habitat people once - a great idea, and very
interesting, but a bit horrifying to a bricks-and-mortar European.