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Lumber & Composites

when to seal a new deck

Hi all,

this question has probably been asked a million times, but I'm in the middle of re-skinning my deck with PT boards and I know I will eventually finish it with a semi-transparent strain - but do I need to seal it first and then stain it when it's sufficiently dry? I've been through a bunch of wood-working forums and some more recent threads seem to indicate that waiting for PT lumber to cure is old school and are new sealers out there that can be (or are specifically formulated to be) applied to fresh PT lumber with high moisture content. So here's what I'd like to know:

1) should I seal it first and then stain, or just stain?
2) are there sealers to can/should be immediately applied to PT lumber?
3) if I seal the deck this summer, do I have time to also stain it this season, or would it have to wait until next spring/summer? (I am in MI).
4) any semi-transparent stain recommendations?


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Posted 2016-07-18T15:17:25+0000  by ae5880 ae5880
Hi ae5880,

Decks and porches present a particularly severe exposure for both the wood and finishes. Most wood members are in a horizontal or flat position. These horizontal surfaces, especially in decks, are often exposed to the direct rays of the sun and tend to collect moisture, so the weathering process is greatly accelerated.


Thus I would recommend finishing the deck asap using a stain such as Behr Solid color weatherproofing Stain.

This product will offer the maximum protection from the suns damaging rays and protect the wood from deterioration. Behr recommends using their # 64 finish stripper followed by their # 63 cleaner prior to the application of the stain for the best results.


Posted 2016-07-18T17:21:30+0000  by Mike_HD_OC

The biggest concern with pressure treated wood is the moisture content. The very process of pressure treating in a giant pressure cooker, forces moisture deep into the grain of the wood. You often can feel the moisture just in handling the wood. It is also noticeably heavy with water.

A few weeks of air drying on the deck in summer will be sufficient to lower the moisture content into single digits, to where a stain would be able to penetrate.

You do not have to worry about "mill glaze" on pressure treated wood, as the very PP process opens up the grain of the wood.

Pressure treated wood is inherently rot resistant. Letting the deck stand for a couple months, or a couples years will not significantly damage it. Sure, staining will slow down the linier cracks in the grain of the wood, but those will eventually occur anyway. Staining will also help prevent staining when someone spills the red wine on the deck.

MIke above suggests a solid hide stain for its superior protection, however, most people don't initially build a deck to look at "painted" wood, they want to see the grain of the wood.

My preference for new decks is a transparent OIL stain. Oils penetrate into the wood and form no surface film. Having no surface film, it will NEVER peel, as acrylic based (water based) can. Oil stains do require periodic yearly or every other year  re-oiling. It is a trade off of more periodic maintenance rather than having to strip the deck every few years.

Oil stains also do not build up and become somewhat opaque, as do acrylic based stains.

ALL exterior stains are their own sealer. They require no other additional top coating. Indeed, a pre-sealing with a product such as Thompson's  would prevent using a colored stain later!

OIl stains are ONE coat only. Acrylic stains are normally two coat products.

Posted 2016-07-19T05:08:12+0000  by ordjen

P.S. Home Depot carries premium oil stains by both Sikkens and Cabots. I have used both over the years during my contracting career and can say both are excellent products.
Posted 2016-07-19T05:11:10+0000  by ordjen

Thanks for the info. My previous deck was stained in solid color, so appreciate not having to strip the deck before re-applying. I assume both clear and semi-transparent strains dot not require stripping before re-applying?

Also, how do you feel about Flood and Thompson products?

thanks again.
Posted 2016-07-19T13:58:49+0000  by ae5880
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