Sanding a Deck: How little can I get away with?
April 24, 2006 4:47 PM   Subscribe

Sanding a Deck: How little can I get away with?

We have a a neglected deck at the back of our house. It's about 700 sq. ft., it was painted at one time but about 70% has worn off. The exposed areas are thoroughly sun bleached and the whole thing is fairly warped, cupped, etc. It's not excactly falling apart, just ugly. It's built of pressure treated wood and I'd guess it to be 20 years old or so. I've used a powerwasher (fun!) to clean the whole thing and against all the warning used the 'laser blast' nozzle to get as much of the remaining paint off as possible. I'm not trying to restore the thing, just clean it up and make it hold up for a few more years.

It's pretty splintery at this point. I plan to use clear deck sealer when weather permits but I suspect it should get a bit of sanding first. I think renting a big drum sander, like you use for floors, would be overkill. Considering ther un-eveness of the surface I imagine it getting caught on corners and grinding off the nailheads that hold the deck together, running amok, etc.

Can I get away with a handheld random orbit sander to just get the high points? Is there some kinds of spongy/flexy sanding device that'd reach below the high points (like the lower areas of a cupped plank)? I don't want to spend more than necessary but I don't want to go through all this to end up with a bed of nails either. I'm a total novice. Any suggestions?
posted by HK10036 to Home & Garden (8 answers total) 1 user marked this as a favorite
Unless the deck fasteners are stainless steel, any sanding you do will remove the galvanized coating on the nail heads and they will quickly rust, even with a clear coating. If the surface is not in good enough shape for a clear finish, you might consider a semi-transparent deck stain.
posted by JackFlash at 5:11 PM on April 24, 2006

See, this is the problem with home-improvement projects. You start with sanding, and you end up with backhoes and concrete pilings and serious marital discord.

If the deck is structurally sound, then just leave it alone. Any serious intervention could create more problems than it solves -- as JackFlash describes. Hand-sand dangerously splintery areas. (If it's way splintery, use cheapo rush mats to cover high-traffic areas.) Apply a good waterproof and UV-resistant sealer or stain to the exposed wood. Keep the gaps between decking boards clear. Check everything in the spring and the fall; replace any rotting sections. (You can find instructions for doing this via google, or at any Lowes or Home Depot or similar. It's not that complicated.)

Until you're ready to replace the whole thing, don't undertake any major work on the deck. Your time and money and emotional capital is far better spent elsewhere.
posted by vetiver at 7:31 PM on April 24, 2006

Pressure treated lumber has so much arsenic on it that they won't use it for zoo animals, and arsenic still comes off the surface even after 15 years out in the rain. Like, Superfund-levels of arsenic (were found under 2 of every 5 pressure-treated swingsets).

So. If you're sanding it, you'll probably want to use one of those hospital-mask-looking things, you'll want to wash your hands before you eat, and you'll want to avoid washing your clothes with kids' clothes, if you have any (and certainly keep kids & pets away from the area while you're doing it).

Oh, snap. I just checked out the ten safety steps for dealing with pressure treated lumber. It all sounded fine until I got to:

#6 Do not pressure wash to clean the surface of arsenic-treated wood... Pressurized water will blast off the upper surface of the wood and spray arsenic-contaminated particles over your yard.

Huh, guess that's why you got those recommendations. Sorry to be the bearer of bad news. I imagine you didn't care about the arsenic. But here's another good one:

#8 Never sand arsenic-treated lumber. If wood is smooth enough that splinters are not a risk, avoid sanding a deck to prepare the surface for sealing—use a simple soap and water wash instead.

So there you have it. The bare minimum -- use soap, water, and disposable rags. See, you're not being lazy -- it's for everyone's health! If you really want to smooth it out, it sounds like it almost might be healthier to use a planer on the sections that are warped upward, (avoiding the nails), so you don't kick out a bunch of dust.

Then, ideally:

#1 Seal the wood at least every six months with standard penetrating deck treatments.


#10 Do not use commercial “deck washing” solutions. These solutions can convert chemicals on the wood to a more toxic form.

And also:

#3 Wash your hands and your children’s hands after every exposure to arsenic-treated wood, especially before eating.

"Why bother?" I asked myself. Aha, because:

"Arsenic isn’t just poisonous in the short term, it causes cancer in the long term. Arsenic is on EPA’s short list of chemicals known to cause cancer in humans." It is absorbed through skin, breathed in via airborne dust, and ingested while eating.

I don't mean to lecture. Good luck. :)
posted by salvia at 11:01 PM on April 24, 2006

Those pressure-treated lumber safety instructions are insanely conservative IMO. I would certainly wear a mask while sanding.

There is no epidemic of arsenic poisoning among people who work with pressure-treated lumber every day.
posted by unSane at 5:28 AM on April 25, 2006

The problem with high-sanding with an orbit sander is that you will end up with a deck which has ugly bare spots. These will be just as obvious if you stain, trust me.

And the reason they don't use PTL for zoo animals is that they typically have stereotypies which involve gnawing any lumber in their compound.

Obviously, if you children have gnawing stereotypies, you should get rid of the PTL.
posted by unSane at 5:33 AM on April 25, 2006

I did exactly what you're talking about last year. I doubt that my deck was made of preserved wood, but it's a bit hard to tell at this stage. My goal is to avoid replacing the deck for another 8-10 years if possible.

Here's what I did: Pressure-wash, then go around and drive in all the screws so the heads are below the wood (only because they rip the paper on the sander). Turn over or replace a couple of very bad boards. Sand with drum sander (fun!) to remove cups and the rest of the paint. Clean up with belt sander. I did a couple of difficult areas just with the belt sander, but it would have taken weeks to do the whole thing like that. Two coats of opaque deck stain. It looks good, and we'll see how long it lasts.

Cost with power washer and drum sander rentals: about $350 CDN, and it took about four weekends.
posted by sneebler at 6:02 AM on April 25, 2006

I'm glad I asked the questions here. As always I get enlightening responses from varied POVs.

I think bypassing the sanding may be the way to go. JackFlash's comment about deteriorating the nails and unSane's point about bare spots are on the mark. Vetiver summed it up nicely.

We have a stretch of sunny days coming so I'll see how it feels when thoroughly dry. We actually like the weathered 'seaside boardwalk' look that the deck has now. Besides, if we made it look too good you might notice what a dump the rest of the house is.

The Arsenic concerns are interesting. But this is Jersey City: the Superfund capitol of the East Coast. I've got 2 gas stations a block away, one of which has just had some sort 'remediation system' installed. We're mid-way between the Lincoln and Holland tunnels and hemmed in by I-95 so we have the emmisions of several zillion NYC bound cars blowing past us every day. I'm not too worried a bit o' arsenic. Well, maybe a little bit worried.
posted by HK10036 at 6:43 AM on April 25, 2006

unsane, I don't know the research about workers, but I dated a builder who disliked working with it because he could feel a difference. (And he was a red stater who personally removed gravel that got embedded in his eyelid, refused to take painkillers for broken bones, and other similarly insane, un-hypersensitive things). Just one example, but also, the wood industry is phasing it out, so that makes me think there's something wrong with it.

But sounds like it does flush from the body pretty quickly, so a project or two is no big deal -- I know it was keeping you up at night, HK ;) but you can rest easy -- the goal is just to prevent ongoing exposure. Like touching the wood railings on your way in the house every day. And so some people recommend not sanding, not to protect yourself, but to avoid scattering it all over the yard, to protect future kids, pets, vegetable growers, etc. -- people who'd get more ongoing exposure.
posted by salvia at 12:17 PM on April 25, 2006

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