Is Vapor Barrier Necessary?

[Lisa]

I want to replace the original aluminum siding on my '65 single wide with hardiboard. I plan on installing new insulation, sealing with latex caulking, priming and painting. Can I get away without adding a vapor barrier? I live in dry climate southern Calif.
Thanks

[Mark Bower]

In some construction circles, whether or not to use a vapor barrier is a battle of pros and cons . Overall the general consensus is 'yes.'

Mark

[Lisa]

P.S. - I am referring to a vapor permeable house wrap that would go between the insulation and the siding; not the 6 mil black plastic under the coach.
I'm trying to save on expenses. Any input would be appreciated.

[Mark Bower]

That's what I meant -- the vapor barrier that goes under the siding.

Mark

[trmimo]

This home is not built to withstand the weight of hardiboard. You probably have 2 or 3" walls. They simply aren't stong enough to carry the weight. Even if you do have 4" walls, you will need to perimeter block the house to carry that much weight. Hardiboard weighs approximately 3 pounds per square foot. The floor and frame are not designed for that much extra weight.