What is the average cost to replace a rotted kitchen sink cabinet floor?

A fair ballpark for this is $250 to $450. alot of that depends on whether you just want a functional floor or somthing that looks like the original cabinet. If a guy shows up with a piece of scrap plywood and knocks it out in two hours, $300 is about the going rate in most mid-sized cities. If you want it primed, painted, and trimmed out to look factory-new, expect to pay on the higher end of that scale. The plumbing in the corner is the biggest headache. Usually, the best move is to cut the new piece of wood into two sections so it can be slid around the pipes, then join them with a support block underneath. A pro will likely use a **multitool** or a jigsaw to get into those tight corners where the supply lines are. It’s a messy job because that wet particle board just crumbles into disgusting chunks when you try to pry it up.

Make sure they don't just screw the new wood down and leave. You want them to treat the area with a fungicide first. Once the new floor is in, have them run a bead of silicone around the entire perimeter. This creates a bathtub effect so if you have a small drip in the future, the water stays on top of the wood where you can see it rather than soaking into the edges and ruining the new board. I'd suggest using **3/4-inch plywood** instead of anything thinner. It’ll give the cabinet its structural integrity back, especially since that bottom board helps keep the whole box square. If you relly want to overbuild it, ask for a piece of 1/2-inch PVC sheet, but that stuff can be pricey and might be overkill for a standard kitchen.

That multitool thing sounds like a lifesaver. I've seen those vibrating ones at the hardware store but never knew what they were for. If I try to do this myself, is there a specific blade I shoud get for wet, crumbly wood? Also, regarding the fungicide—can I just use a spray bottle with some bleach water? I’m worried about the smell sticking around even after the new plywood is in. I'm also curious if 3/4-inch is going to make the floor sit higher than before, or if the original particle board is ussually that thick anyway.

Skip the bleach. It’s mostly water and doesn't actually kill the mold roots in porous wood frames. Grab a bottle of Concrobium; it’s odorless and handles the spores properly. For the multitool, get a "Japan tooth" blade. Those larger, aggressive teeth won't get gummed up by the wet wood pulp as fast as a fine-tooth blade.

If you're alredy in there, slap some cheap peel-and-stick vinyl tile onto the new plywood before you silicone the edges. It's a tiny cost that makes future spills way easier to clean up and protects the wood. Just keep a steady hand around those supply lines so you don't nick the copper.

If you're going the DIY route, check the side walls of the cabinet while the old floor is out. That wet particle board often pulls the staples right out of the side panels. If the sides are still solid, screw some 1x2 pine cleats around the inside perimeter first. This gives your new plywood a solid ledge to sit on so you aren't just relying on nails or glue. It makes the whole thing way sturdier, especally if you store heavy detergent bottles under there. Much easier than trying to screw into the edge of a thin cabinet wall.

Make sure you paint or seal the edges and the underside of that plywood before you install it. Most people only finish the top, but if there's another leak, the water wicks into the raw edges and delaminates the layers.

Also, pick up some split-ring escutcheon plates for those supply lines. Since you’re cutting the board to fit around the pipes, the holes usally look a bit rough. Snapping those plastic rings on at the end covers the gap and makes the whole job look clean for about three bucks. It's a small detail that prevents debris from falling into the dark void under the cabinet.