Argthtjtr

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)

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.

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).