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I recently built a deck in my backyard with pressure treated wood and was also planning on staining it for color and weather proofing. However all of the wood came very wet, cutting through the pieces produced globs of wet sawdust even. So I asked a friend about his experience staining his deck and he advised me to wait a year for it to dry before I stain to avoid any complications due to trapping moisture. I would like to apply the stain asap for both aesthetics and for the weather proofing, as the coming 8 month long winter hits -40 Celsius. the deck has been complete for about 1 month which has also been quite hot, so it did dry out and contract a little bit already by the way.

Should I wait a full year for the deck to dry out or stain sooner rather than later?

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    Staining shouldn't really have any effect in sealing in moisture. A sealant might, but you haven't indicated that you are using one. Anyway, there isn't really any finish that will arrest the movement of water in and out of the wood completely (save maybe epoxy), so it may be a moot point. – grfrazee Aug 25 '15 at 1:58
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So I asked a friend about his experience staining his deck and he advised me to wait a year for it to dry before I stain to avoid any complications due to trapping moisture.

Unfortunately this will relate to the irregular use of the word 'stain' in woodworking circles, and by manufacturers, which can and often does lead to confusion. By definition a stain should be a colouring agent only, but the word stain is now used, often without qualification, for products that are in essence coloured varnish or another protective finish.

A true stain can in theory be used on wood that isn't fully dry without much issue, except for preventing the wood from taking the colour as strongly as it would otherwise. If the 'stain' is on the other hand a coloured varnish or other finish you would not want to do this as there could be significant problems with adhesion, leading to excessive weathering down the line (irrespective of whether the stain is oil-based or features water cleanup).

It's likely not much help but the ideal way to check how dry your wood is would be to take a piece that has been outside and cut through it, see firsthand how wet it is in the interior.

I would like to apply the stain asap for both aesthetics and for the weather proofing

For what it's worth, a year's exposure to the elements shouldn't harm most woods to any significant degree. You will get some degree of surface discolouration (greying/silvering) that you're likely not going to be happy with, but the wood's structural integrity should be unaffected.

Drying times for wood

Re. the year to dry out that your friend mentions, that sounds excessive but there's a guideline timeframe often mentioned in woodworking circles in relation to wood drying of about a year per inch (25mm) of thickness.

This is a very broad generalisation however, and is actually really for hardwoods specifically, but the drying times for wood species vary hugely due to the differences in their structure and density. And anyway that relates to wood drying out from green (freshly cut).

With your decking material, whatever it is, presumably it was kiln-dried wood initially that then became waterlogged due to less-than-ideal storage conditions. So even if the moisture content of the wood when it was delivered was the same as green wood this is actually quite different (because the water is stored in the wood's structure differently).

As a result there's no reason to suppose that your wood wouldn't get to an acceptable moisture content — perhaps 14-18% — in a far shorter timeframe than the suggested year, exposed to good ventilation and dry, sunny weather.

If the weather where you are seems set to stay good it wouldn't hurt to wait a bit longer, but a month of drying in good conditions could be enough.

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    It's 'wet' from the the pressure treatment. – bowlturner Aug 25 '15 at 13:33
  • Great answer, and I am very inexperienced with the proper lingo so I apologize for that. – Hatandboots Aug 25 '15 at 14:47
  • @bowlturner, surely it would be allowed to dry after pressure treating? I can't imagine it could be sold with wet preservative coming out of it for legal reasons, that's a toxic chemical in liquid form. – Graphus Aug 25 '15 at 17:48
  • maybe. But pressure treated always seems to be pretty wet while other lumber never is. I suppose it's possible that the pressure treated stuff is the only stuff that sits outside, but I've had boards that are heavier than sitting in the rain could account for, like storing them in a lake... – bowlturner Aug 25 '15 at 18:30
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Pressure treated wood really could use a year to dry out before sealing it. The year won't bother the wood in the weather at all. Do you need a full year? No but you might not have enough time to continue letting it dry this fall before it gets to cold to apply the stain/seal. If all you are going to do is stain it, it might be fine by now, but a stain will apply more evenly if the wood is evenly dry. The pressure treatment is done to help it last through weather and the only reason you would 'need' to do anything this fall is for aesthetics.1

I put up a new deck last fall and it's been a whole year now, and the winter and the summer haven't bothered the wood at all.

Sealing it is more important for the wood to be dry.

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