My friends just bought a new house that has a deck that has gone mossy/moldy. The sellers pressure washed the deck and replaced a few soft boards, but the real problem is that there isn’t enough gap between boards for good drainage

I’ve suggested lifting the deck boards and regapping them but with all of the other repairs to be made, my friend was considering running a circular saw down each gap and taking a little bit of wood off each board

Is there a shortcut way to do this? I would think that a circular saw would leave a corner that’s more likely to split and splinter as it’s no longer rounded over, but a router would be a royal pain to keep straight the whole length of each board

I don’t even know if it’s nailed or screwed down, as it was buried in snow when I was last over there. (I suspect it’d be easier to lift a nailed down deck than a screwed down one)

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    I am skeptical that there's not enough gap between the planks to drain. Pressure treated is sold so wet that even if you install it with zero gap there's a pretty nice gap when it dries. So it's very hard to install with too little gap. If on the other hand it was installed with the cupped side up that's going to be harder to correct. Feb 12 '19 at 19:14
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    @batsplatsterson Yep, I made the mistake of gapping my deck with 16 penny nails and now have some quite large gaps after the deck dried for a season or two :( Feb 12 '19 at 20:47
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    @batsplatsterson : I wouldn't be surprised if the guy sat on the wood for a bit before finally installing it, so it had a chance to dry first. There are a lot of odd things in this house. As best I've been able to figure out, he was a plumber, so he knew a trade, and had lots of access to other trades, but he was only middling in the others. (pull-down attic stairs don't have clearance to come down, chimney was never finished, there's a sink rough-in in a hallway, there's a bar-like area in the kitchen but it's a step up so you risk breaking a neck if using it, etc.)
    – Joe
    Feb 13 '19 at 17:41

You could install three identical blades in your circular saw with the teeth staggered, then run that down the channel. The saw should follow the gap fairly well, but you'll want to brace the saw with a firm grip to prevent wobble and keep things looking very straight. This should get you about 5/16". Be sure to set the depth properly to avoid damaging your joists, and be aware of the increased tendency for kickback.

Find a roundover router bit with a small guide that just fits the gap, and run that down as well. If you're lucky you can just run once in each direction (this reduces fibrous texture with softwood). If the bit guide is too narrow you'll need to go both directions while in contact with each board.

I'd actually borrow or rent a random-orbit (plate style) floor sander and get things level beforehand. If the boards aren't perfectly flat with respect to each other your bullnose will vary quite a bit.

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    One thing with decks, the boards are cupped for reason. The cupped side goes up so water will shed off and into the gap between boards. @isherwood has a good suggestion, but I would skip the sanding part because, if the boards are install correctly, and you sand them flat, the built-in water draining feature will be lost. You could also use a spare board and screw it down the length of the board at the distance you want the edge to be cut...a saw guide board only partially screwed in so it is easy to remove. Then you have a straight edge and when you cut, the saw will go fairly straight and gi
    – Jeff Cates
    Feb 12 '19 at 17:11
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    Deck boards aren't deliberately cupped. The natural grain pattern can cause them to do so, but warpage due to sunlight and retained moisture underneath has a greater effect. I don't consider that a concern.
    – isherwood
    Feb 12 '19 at 17:12
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    I think you're hearing repeated false wisdom. Look at a brand new bunk of decking and you'll probably see that they're perfectly flat. Synthetic decking, maybe.
    – isherwood
    Feb 12 '19 at 17:21
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    I work in a lumber mill boards are rough cut then run through a planer/ edger. You may think they are purposely cupped but this is because of the small and I mean small trees that are being milled today, 50 years ago over 1/2 of the wood my plant uses to produce lumber would gone to a boiler for power / steam production or chipper for paper. Isherwood is correct.
    – Ed Beal
    Feb 12 '19 at 18:03
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    @Joe, that's probably not a reliable way to go. The next board may not be perfectly parallel or straight itself. I'd give it a try somewhere inconspicuous and see how it tracks. If it's not going well, consider drilling and tapping for a 3/16" screw right through the saw table, near the front edge, to act as a guide pin. This should lock the saw on track really nicely. Countersink the hole a bit to make sure it doesn't scar up future workpieces.
    – isherwood
    Feb 13 '19 at 18:23

I recommend the Saw Guide by Lounsbury Products. The guide makes it easy to use a circular saw and make precise cuts along the gap between decking without wandering or gouging into the boards. Watch this video to see how it works. https://www.youtube.com/watch?v=6K-g1KjRqUQ

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    Welcome, Rick. That seems like a good solution. If you have an affiliation with the vendor, please disclose that.
    – isherwood
    May 5 '20 at 19:49

If it's moldy, lifting deck boards can usually be done with a swift kick... A crowbar and a 5lb sledge will pull it right up, if not.

If you decide to pull them up and reuse them, pressure wash it first to see as many fasteners as possible and pull 'em out. If it's nailed down I either wouldn't pull them or I wouldn't reuse them. If they used nails the boards are probably 20yo and done for anyway. Screws you can pull or they'll snap off anyway, but with rusty nails they're always be some crap left sticking out somewhere.

I'd like to see a picture first (and know how lose everything is), but that's only to say if you should bother to pull the boards, or just wash it every year. Give a good pound with the sledge on a few boards to check the integrity, and especially the stairs. Check all fasteners for obscene amounts of rust, such as the bolts for the railings, metal joist hangers and stair hangers. Replace as necessary. Everyone inherits a slippery deck, but those are the other things you need to check, and keep an eye on from now on.

I would not be cutting them in place; that's just going to look like crap, and splinter. But if I was going to go through the work of pulling the wood boards, I'd probably be replacing them with composite decking that you install with hidden claw spacers (I haven't had a single "Tiger Claw" fail yet, 10 years in).

  • There was a layer of something slimy on them -- they're not rotted through, so the boards aren't loose. And my experience with composite decking in our area is that it's horrible -- gets way too hot to be usable in the summer unless you also build something to shade it. I'll try to get a picture the next time I'm there.
    – Joe
    Feb 13 '19 at 17:49
  • I'd argue that following my procedure the boards look nearly identical to stock. Why do you say it would look bad? It's mostly a matter of craftsmanship.
    – isherwood
    Feb 13 '19 at 18:25
  • I wouldn't be counting on my ability to cut 1000' worth of straight cuts, on my hands and knees, with a circular saw. I'd rather put it all on a bench and rework the boards one at a time while I'm standing up, fighting fasteners that are half gone anyway instead of my knees. It just sounds like a lot of work to simply archive a drainage gap; when I come to fix a deck there's always some worse problem I must fix first, that's not on the client's docket. (but it doesn't sound like the OP's deck is that all that bad)
    – Mazura
    Feb 13 '19 at 18:40
  • @Joe - the boards will almost never rot; the metal fasteners will. Especially if they're crappy 'exterior' drywall screws. The picture I have in my head is what it'd look like when you'd want to call someone one in to fix it - all out of wack (cutting the broads like that never's been a solution for me, unless we really wanted to reuse the boards and they were all messed up; needing planned down/ reshaping. But they'd better be something better than plain arsenic treated pine, or if say, there was an exceptional amount of material that's reusable.
    – Mazura
    Feb 13 '19 at 18:53
  • Go big or go home. Just pressure wash it and see how bad it gets this year (it could have 10y of slick on it) Or lets get serious about these cans of worms known as 'decks', and get into it. (you've been warned ;p - decks are money pits, and once you pressure wash it you'll think you have to do it again every year - which you should)
    – Mazura
    Feb 13 '19 at 19:05

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