Interior undercoat under exterior paint?

by Nell

Can I use an interior undercoat/primer for external use? The overcoat paint is exterior :)

Thanks in advance.

Hi Nell,

It depends on the primer itself. I know of painters that have used interior primers, along with an exterior top coat, with no resulting issues. And they did so under very harsh weather conditions.

Keep in mind though, that if you do so, there is no guarantee that your interior undercoat will work. Reason being is that exterior products are manufactured specifically to stand up to different types of environmental conditions along with deterring insects and fungi. Even so, an interior primer may work just fine for the type of exterior project that your doing.

If you do decide to give it a go I do recommend that the surface being coated is clean, dry and free of any flaking or pealing debris.

Start by applying the primer, let it thoroughly dry, lightly sand it and then apply at least two coats of high quality exterior top coat.

If your still concerned as to whether your interior primer will work then I would suggest using the primer and paint on a test board (one that's laid directly out in the elements).

Of course this would put your project off for a year but it would save you from unnecessarily having to buy more primer.


Comments for Interior undercoat under exterior paint?

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Sep 07, 2012
Thank you
by: Anonymous

Thanks Shawn for your advice :)

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