Tar Paper

[Joe]

What is the logic for using tar paper behind vinyl siding and under ashphalt shingles? Curious. Thanks

[Cody Hart]

[Tomeshew]

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

[George]

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 c>

[cdg]

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.

[Leon]

In the south the vapor barrier goes on the outside of the studs.

[JackD]

Yes, it is quite useful to have a backup when this has occured.

-Jack "Belt and Suspenders" man

[Andy Dingley]

That must come as a shock to someone from Microsoft, but there's still some diversity in the world.

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.