[ratherbefishing]

I'm about to install hardboard (Masonite) siding on an addition to my house. It's 12" wide, installed with about a 8.5 inch exposure to match esisting 1x10s. I've been advised to prime the backsides of the boards before installation for longer life.

Do I need to use exterior primer, or would this be a good way to use up some partial cans of paint that are leftover from other projects?

Thanks!

 

[jsheridan]

Anything that will be exposed to the elements needs exterior primer, in this case it would be the cold, so yes, exterior. The idea of backpriming is to create a vapor barrier, so you want the least permeability. To me that would be oil, no latex.