Is it ok to wash wood before painting

Old 11-14-18, 10:25 PM
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Is it ok to wash wood before painting

I have an outdoor patio cover that I let go too long before repainting. There were sections on the top pieces where the paint peeled off and the wood turned gray. I have scraped and sanded those sections and now fresh wood is exposed. I've given a light sanding to the rest of the patio cover where the paint is still ok, but it's dirty.

I would like to wash the whole patio cover before painting it so it's a clean surface. Is it a bad idea to get the areas with bare wood exposed wet? I would let it fully dry before applying any paint.
Old 11-14-18, 11:54 PM
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That is perfectly good idea, you dont want to paint over dirt.

A good cleaner is TSP but it's very very strong stuff so use plenty of protection and as you noted let it try thoroughly!
Old 11-15-18, 02:29 AM
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Washing the exterior prior to painting should almost always be part of the prep. TSP is a great detergent but it needs to be rinsed well as leftover residue can affect paint adhesion. If there is mildew - use bleach. Bleach water is my go to cleaner for exteriors, I add TSP if there is extra grime that needs to be cleaned off.
Old 11-28-18, 10:27 AM
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One problem could be your definition of the phrase "fully dry". It means different things to different people.

Power washing can drive water up under the siding, so you always want to try to spray downward, not up under the siding. But it still happens no matter how careful you are. Bare siding can also absorb moisture like a sponge. While it may be dry to the touch, the wood could still have a high moisture content. And not all areas dry evenly. If painted too soon, that moisture can affect the adhesion of the paint.

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