Replies

1. 
   MarkH | Dec 30, 2009 03:07pm | #1

   I would try to cover the old bottom with some new plywood. Most cabinets are stapled together particleboard and are hard to work on unless they are removed and torn apart.

2. 
   rdesigns | Dec 30, 2009 03:26pm | #2

   Similar to MarkH, skin over the old with new, using 1/4" plywood. You may have to sand or scrape swollen portions of the old if it was particle board in order to get the new sheet to lay flat.

   For the neatest job, you'll need to diconnect any pipes that penetrate the floor and drill holes in the new skin so that you can set the new piece in place.

   You may need to do a 2-piece skin so that you can maneuver it into the door openings and position it in place. If you end up with gaps at the edges, just install quarter round mouldings to cover.

3. 
   JTC1 | Dec 30, 2009 03:30pm | #3

   Same as what MarkH said.

   Eliminate the leak then cover it with new plywood - exterior,sanded, sheathing grade, birch, oak.....your choice!

   Make sure that all the remaining "original" plywood / particle board is dry before covering. Cut damp old away if needed. Depending on how large of an area is removed (or rotted) you may want to install a strategically placed block or two to help support the new plywood.

   Jim

1. 
   pm22 | Dec 30, 2009 07:47pm | #4

   What I did is eliminate that bottom altogether. Who'se gonna miss it? You gain 3 or 4" of storage room.

   Just paint the new bottom with heavy duty, oil-based paint and caulk the edges.

   ~Peter

4. 
   DanH | Dec 30, 2009 09:28pm | #5

   Yeah, I'm with the others --
   Yeah, I'm with the others -- cut out the bad sections, but leave at least 6" around most of the perimeter (except where it's rotten), then attach the new bottom to that. You can probably make the new bottom in 2-3 sections, to make it easier to install around the pipes. Screw it to the old with short drywall/deck screws about every 6" around the perimeter.

   Use at least 1/4" plywood, maybe 3/8" -- 1/2" if you're really going to load it down with stuff. And if there will be heavy loads consider putting a brace down the middle -- just a length of 2x ripped to the right height to fit between the "real" floor and the cabinet bottom, tacked in place with 2-3 screws.

5. 
   9ENGEL | Dec 31, 2009 09:09am | #6

   Everyone else sounds correct, except I plan on doing the same thing with azek when I get around to it.

6. 
   k1c | Dec 31, 2009 12:47pm | #7

   Depending on how far you want to go with repair, you can line the bottom with plywood (best solution, and finish with paint or polyurethane) or just line the whole bottom with shelf liner or even aluminum foil. I find the most cabinet floor under the sink have some damage from not just water but also wet rag, sponge, liquid soap, etc.

   Measure the floor and deduct 1/8 or 1/4 from all sides (tight measurement and cut may get you into more trouble anyway). Have the ply cut at Homedepot and cut the piece in half if you think you'll have problem getting the whole piece into the cabinet opening. Cut a cardboard test piece and try. Trap, electricals, grinder, all can get in your way. If damaged floor is swollen, chisel out flat and either screw or glue the new floor in. Use same glue (use urethane based adhesive - paintable) to finish the gap. Hope this helps.

7. 
   mikeys | Jan 03, 2010 12:35pm | #8

   Cutting out rot and overlaying is the way.

   A suggestion for the new bottom is cut the piece a little small, layout pipe locations, drill for pipes(a little oversized), "connect the dots" by cutting from edge to hole to hole to hole to edge.

   You should then be able to lay the new floor neatly in two pieces without having to remove and replace pipes.

8. 
   IdahoDon | Jan 03, 2010 06:46pm | #9

   Personally I'd carefully
   Personally I'd carefully scribe a line around the perimeter of the damaged bottom about an inch and a half from the cabinet sides (1-1/2" wood scraps are normally easy to find in my truck). Now you cut to the outside of the scribed line and remove the damaged part--cutting slots so pipes slide out easily is normally needed. Demo the 1" strip around the inside of the cabinet if it doesn't fall off on it's own.

   To cut a new piece you already have an exact template of what you need--simply use a 1-1/2" strip of wood aligned with your scribed line to give the exact width and depth.

   I wouldn't use anything but 3/4" ply--look for the flattest sheets. This is a perfect time to test your plumbing skills and replace all the valves that penetrate the new ply--not only is it cheap insurace but the results are more professional if you don't have to piece in the bottom.

   To support the ply I use ply strips screwed/glued 3/4" below the desired finished level. This also provides a good base to attach the bottom to rather than relying on the particle board sides.

   Then the ply is primed and edges are caulked to eliminate any small gaps and a good quality, gloss, bright white, 100% acrylic trim paint is used for a light colored and durable surface.

   I'll let others suggest how to half asss it.

1. 
   Mark | Jan 10, 2010 12:21pm | #10

   I think Don's last sentence
   I think Don's last sentence was awfully uncalled for.

   It is, after all, a sink base cabinet... not a bomb shelter. Installing a 1/4" plywood bottom over the top of the existing cabinet floor after cutting out the damaged portions will make that the most structurally sound cabinet in that whole house.

   So what's wrong with that?