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mebarry8
Restoring an old deck

Our deck is grey and weathered and a new one is a few years away. In the meantime, we thought we’d clean and re-stain it. We powerwashed it – though afterwards we read that maybe we shouldn’t have, if it’s pressure treated, and that we shouldn’t sand the deck for the same reason. The problem is, we don’t know if it’s pressure treated. The inspector, when we bought the house, said it isn’t, but consequent contractors said that it is. I know pressure treated wood has the greenish tint but I don’t know if any tint on the wood now is because of residual mildew or not? In any case, the wood, though now a bit cleaner, still has a lot of deep grooves. Can we sand it down a bit and then restain? Should we be concerned that the wood might be pressure treated?

dj1
Re: Restoring an old deck

You can identify old pressure treated lumber by the 1/2" long markings on its surface. Also, some may still have a stapled label on either end. Sometimes the green color is faded and sometimes it's not green at all.

Sanding PT lumber will release unwanted chemicals into the air.

I would rather replace planks that are badly deteriorated.

ordjen
Re: Restoring an old deck

Personally, even it if were pressure treated, I would not hesitate to pressure wash or sand the decking material. An aged pp deck will have already leached out much of the original preservative. Would I wear a good dust mask - yes! I might even wash my work clothes in a separate wash load.

Are all the carpenters dead who cut into the new, fresh pressure treated lumber years ago while building those decks? We have to use a little common sense. Would I want to sand pp wood on a daily basis - probably not. Nor would I want to remove asbestos or lead on a daily basis unless I were highly protected against it. But a one time minimal exposure is exactly that.

I lived in my former house in suburban
Chicago for 30 years. I built a pressure treated deck and stripped and sanded it at least twice during those years. Even the joists were in full contact with the ground. That deck was in perfect shape when I sold the house. And, to the best of my knowledge, I am in pretty good shape too for an old guy! :)

mebarry8
Re: Restoring an old deck

I'm inclined to take my chances and sand away!

What type of sander is best?

jkirk
Re: Restoring an old deck

an aggresive 6" orbital works well, or you can rent a drum sander though their tricky to use and remove quite a bit of material quickly if youve never used one before

ordjen
Re: Restoring an old deck

The problem with using too large a sander is that most decks are not really flat. The decking boards are either bowed or cupped. A large, broad sander will flatten the bows while riding right over the cups. I have done even rather large decks using my Bosch belt sander which uses a 24X4 inch belt. A belt sander will follow the contour of the boards without taking excess wood off. You should make a first pass using a rather course paper like 50 grit. The course grit will not clog so quickly. Surprisingly, if you stay parallel to the grain, the sanding texture is not too course. Finish buy going over with about a 100 grit. Don't be tempted to make the deck super smooth with a fine grit, as heavy sanding can close the grain of the wood, imparting a "mill glaze". This will impair the ability of the new stain to penetrate deeply into the wood. Don't forget to go over the deck driving the screws down or setting the decking nails. Screws and nails tear up sandpaper badly.

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