How to Replace Under Sink Cabinet Floor Like a Pro: Step-by-Step Guide to Replacing Your Under Sink Cabinet Floor for a Fresh, Durable Finish

If you’ve ever peeked under your kitchen or bathroom sink, you know that the cabinet floor can take a beating. Leaks, spills, and cleaning supplies all combine to wear down the floor, causing stains, sagging, or even rotting. Replacing your under sink cabinet floor doesn’t require a contractor—it’s totally possible as a DIY weekend project, and knowing how to do it can save you hundreds in professional repairs. In my years as an interior designer, I’ve seen and fixed plenty of under-sink disasters, and here I’ll walk you through a foolproof replacement process.

Before we get started, let’s outline what you’ll need: plywood or waterproof board, a saw, drill, measuring tape, exterior-grade wood glue, screws, and sealing paint. Take a minute to review your cabinet shape and size so you have accurate measurements. (For more on mapping and planning, check out how to quickly draw accurate floor layouts with a 2D floor planner.)

Project Planning

Start by emptying your cabinet completely. This is the time to toss expired cleaning products and take stock of leaks—if you smell mildew or see water stains, fix plumbing issues first, or your shiny new floor won’t last. Measure the length and width of the interior cabinet base, as well as any notches for pipes. I recommend sketching a simple layout before you cut any new material, and you might even use a cardboard template for tricky corners.

Choose the Right Tools

I always suggest using exterior-grade plywood or a waterproof MDF board for best longevity beneath the sink. Standard kitchen cabinets are typically made with 3/4" thick plywood, but measure your original board to match thickness. To speed up your workflow, a cordless drill and circular saw will save you time, and if curves are involved, a jigsaw helps greatly.

Level of Detail & Time

Depending on your cabinet’s complexity—especially if there are many pipes—the cutting and fitting process may take more time. Removing the old floor usually means carefully prying it free. Wear gloves to avoid injury from staples or old adhesives. Once the space is clear, dry-fit your new board before gluing or screwing it down. I once worked on a home where a DIYer misjudged their sink’s curve and ended up recutting twice – templates help!

Case Study: Quick Fix in a Busy Family Kitchen

One of my favorite projects was for a family of five whose under-sink area had suffered from years of slow leaks. The cabinet base was soft and unsafe to store anything. After fixing the pipe, we measured carefully and replaced the warped base with waterproof plywood, sealing all the edges with outdoor-grade paint. The family even used a free floor plan creator to visualize the cabinet update in their kitchen remodel! Two years later, the floor is still looking fresh and dry.

Budget & Time Planning

The great news? Most DIYers can replace an under sink cabinet floor for under $50 in materials. If you need to rent or buy power tools, costs will increase a bit. Expect to spend 2–4 hours, depending on complexity and your comfort with tools. For step-by-step visualization and efficiency, some folks use a room planner app to help with accurate measurements and material planning.

FAQ

1. How do I know if my under sink cabinet floor needs replacing?
2. If the base feels soft, has water stains, smells musty, or is visibly sagging/rotting, it’s probably time for a replacement. It’s crucial to address leaks and moisture sources first.
3. What’s the best material to use for an under sink cabinet floor?
4. Exterior-grade plywood or waterproof MDF work best—avoid standard particleboard, which can swell quickly if exposed to leaks.
5. Can I install a new floor over the old one?
6. Yes, if the old base is flat and dry, but for best results, remove the damaged material so mold doesn’t develop underneath.
7. How do I seal the new floor against water?
8. Use outdoor-grade sealing paint on all sides of your new floorboard, particularly the edges and any cutouts for plumbing.
9. Is this a project a beginner can handle?
10. Yes! With careful measurement and the right materials, replacing an under sink cabinet floor is absolutely DIY-friendly. Using a DIY-focused design tool can help you plan the process visually.
11. Do I need to remove the sink to replace the floor?
12. Usually, no—you can work around most plumbing, though tight spaces will require some maneuvering or small cuts for pipes.
13. Should I use glue or screws?
14. Both! Use waterproof wood glue under the board for extra security, then secure with screws at the corners for a sturdy finish.
15. How long will the replacement last?
16. With waterproofing and leak prevention, your new under sink cabinet floor should last as long as the cabinet itself—often decades.
17. What if my cabinet has extensive mold?
18. Remove all affected wood, clean the area thoroughly with a mold killer, and let it dry completely before installing new material.
19. Where can I get a cabinet floor cut to size?
20. Many home improvement stores will cut wood to your specifications if you bring accurate measurements or a cardboard template.
21. What finishing touches can make the new floor even more durable?
22. Install removable waterproof liners, or paint with two coats of marine varnish for extra protection against drips and spills.
23. Any tips for working around curved plumbing?
24. Use a flexible measuring tape and create a cardboard template—this helps you cut precise notches without wasting materials. Visual planners, like home design software tools, can also help anticipate tricky spots.