How can I fix standing water on a deck with zero board gaps?

Running a circular saw trough those joints isn't crazy at all; it's actually the standard fix for a deck that's been installed too tight. I’ve seen this plenty of times where someone installs wet pressure-treated lumber butted up tight, thinking it will shrink, but then it stays swollen or gets even tighter during a wet season. You basially have a giant pool liner right now, and that's a nightmare for your foundation.

Set your **circular saw** depth so it’s just a hair deeper than the thickness of the boards. You don't want to be carving deep notches into your joists, but a tiny nick in the top of the joist won't hurt anything structurally. If you're worried about keeping the lines perfectly straight, you can clamp a straight edge down, but usually, just following the existing seam by eye works well enough since the blade will want to follow the path of least resistance.

One thing to watch for is the debris. Sawing through wet wood is going to create a lot of mushy sawdust that might clog up the very gaps you’re trying to create. Have a shop vac or a leaf blower handy to keep the line clear as you go. You'll likely want to use a **carbide-tipped blade** because you might hit a stray nail or screw head if the original installer wasn't perfectly precise with thier fastening. Once the water finally drains, you have to deal with the raw edges you just created. Cutting those joints opens up the wood grain to the elements. Wait for a dry spell, let the wood realy breathe, and then get some end-cut sealer or a bit of stain in those gaps. If you leave them raw, those boards will start rotting from the inside out within a few seasons. Also, check that the ground under the deck actually slopes away from the house slab. If the water drops through the deck but just sits against the house on the dirt, you've only solved half the problem.

That circular saw trick sounds like a lifesaver but also pretty scary for someone who hasn't used power tools much. If the wood is allready swollen and tight, is there a big risk of the blade binding or kicking back? I'm also wondering about the gap size. A standard blade is pretty thin, so does one pass realy give enugh room for the water to drain properly? I'd be worried the wood might just swell right back up and seal the new gap if the rain keeps coming like this.

Binding is a legit concern when cutting through wet, swollen lumber. To keep the saw from kicking back, use a fresh, sharp blade and don't rush. If the wood starts pinching, wedge a small flathead screwdriver or shim into the start of the cut to keep the gap open as you move along.

Regarding the gap size, a standard 1/8-inch kerf is usally the bare minimum. If you want better drainage, look for a "full-kerf" blade rather than a "thin-kerf" one. They move more material and give you a wider channel that's less likely to clog up with gunk or organic debris down the road.

To get a wider gap without doing double passes, look for a thick kerf blade specifically. They make some that are closer to 3/16 or even 1/4 inch, wich is perfect for drainage and won't clog as easily. One thing I'll add—since your boards are so tight, make sure you're wearing eye protection and maybe a face shield. Sawing wet, pressure-treated wood sends a nasty slurry of wet sawdust and chemicals flying right back at you. It’s way messier than cutting dry lumber. Also, have some spare blades on hand. Wet PT wood is surprisingly abrasive and will dull a blade way faster than you'd expect.