Maximum time you can leave undercoat before glossing?

Question

I primed and undercoated some exterior woodwork several months ago. I  couldn’t get to gloss it then. Will the undercoat still be ok to apply gloss to or will it have deteriorated?

Guy · Accepted Answer

Hello,

You should, check the condition, lightly key the surfaces and apply another coat before applying the topcoat.

Volodymyr · Answer

If the woodwork has been sitting for several months since you applied the undercoat, it’s worth giving it a bit of attention before going straight on with the gloss. The undercoat itself probably hasn’t completely failed, but over time it will have picked up dust, dirt, and possibly gone a bit chalky on the surface — especially if it’s been exposed to the weather.

Give it a light sand to remove the surface oxidation and provide a key for the gloss, then wipe it down with a damp cloth or tack rag to get rid of any residue. If the coating still feels firm and intact, you can go ahead and gloss straight over it.

However, if you notice any flaking, powdery areas, or bare wood showing through, it’s better to apply a fresh coat of undercoat first. That will give your gloss a solid base and help it last much longer.

Frincu · Answer

Given the timing, the undercoat will likely have deteriorated slightly. You'll need to lightly sand it, clean it throughly, and consider applying a fresh coat of undercoat before glossing.

Maximum time you can leave undercoat before glossing?

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