I’ve had mixed results with MDF, honestly. It’s definitely smoother for painting, but I did get a bit of chipping around the edges when I used a regular circular saw blade. Maybe a finer tooth blade would’ve helped? I’m curious if anyone’s tried those composite panels in areas with lots of moisture—do they actually hold up better than plywood under the sink, or is it just marketing hype?
JUST PUT IN A NEW KITCHEN SINK AND WONDERING IF ANYONE ELSE STRUGGLED THIS MUCH
- Totally agree about MDF being smoother for paint—makes a huge difference for finish work.
- Edge chipping is super common with standard blades. I usually switch to a fine-tooth or even a laminate blade when I need a cleaner cut.
- For moisture-prone spots, I’ve found composite panels can be a bit hit or miss. They’re marketed as more water-resistant, but if there’s a leak, they’ll still swell up faster than good plywood.
- Plywood’s not perfect either, but I’ve seen it hold up better under sinks, especially if you seal the edges.
- If you want something really bulletproof, marine-grade ply or even a PVC panel is worth considering, though it’s pricier.
- Had a client once who insisted on MDF under the sink—regretted it after a year when it started to puff up. Just my two cents...
JUST PUT IN A NEW KITCHEN SINK AND WONDERING IF ANYONE ELSE STRUGGLED THIS MUCH
Plywood’s not perfect either, but I’ve seen it hold up better under sinks, especially if you seal the edges.
That’s been my experience too—plywood’s not invincible, but it’s a lot more forgiving than MDF when things get damp. I always cringe a little when I see MDF under a sink. It’s like, sure, it paints up nice, but one leaky P-trap and you’re looking at a science experiment growing under there.
Here’s my usual routine for under-sink installs (learned the hard way after a few callbacks):
1. Cut the plywood to fit, dry-fit everything first because nothing’s ever square in an old house.
2. Sand the edges smooth—splinters are no fun when you’re crawling around on your back.
3. Hit all the cut edges with a good waterproof sealer or even just some exterior-grade paint if that’s what I’ve got on hand.
4. If I’m feeling extra cautious (or paranoid), I’ll run a bead of silicone around the perimeter before dropping it in place. That way, if water does get loose, it’s got nowhere to go.
I’ve tried those composite panels too, and honestly... mixed results. They sound great on paper, but like you said, they’ll still swell up if you get a real leak. PVC panels are kind of overkill unless you’re dealing with chronic leaks or maybe rental units where nobody’s watching for drips.
Funny story—one time I had a client who wanted to save money and insisted on using leftover MDF from another project under their sink. Fast forward six months: they call me back because “the floor feels weird.” Open the cabinet and it looked like someone had baked a loaf of bread under there. Lesson learned.
Cutting-wise, totally agree about blades making all the difference. Fine-tooth or laminate blades are worth every penny if you want clean edges and less cursing.
At the end of the day, nothing’s totally waterproof unless you go full plastic or stainless, but sealing up plywood gets you 90% there without breaking the bank. Just my two cents—hope your new sink is treating you better now!
At the end of the day, nothing’s totally waterproof unless you go full plastic or stainless, but sealing up plywood gets you 90% there without breaking the bank.
That’s pretty much been my takeaway too. I’ve had decent luck with marine-grade plywood, though it’s pricier and maybe overkill unless you’re super worried about leaks. Funny enough, I once lined the bottom of a cabinet with leftover linoleum scraps—didn’t look pretty but caught a slow leak before it wrecked anything. Sometimes the “ugly but functional” route just works.
Honestly, I get the appeal of sealing up plywood or using marine-grade, but I think there are better options if you’re looking at long-term durability and sustainability. Recycled HDPE panels or even composite boards hold up way better against water and don’t off-gas like some plywood sealants do. They’re not always the cheapest, but you end up replacing less often. I tried the linoleum trick once too—definitely functional, but I couldn’t get past the look after a while. Sometimes ugly works, but it’s worth considering what’s going to last without constant patch jobs.
