Plywood or MDF for Kitchen Cabinets? The Questions That Actually Matter

Plywood or MDF. It's the first fork in the road on pretty much every cabinet job, and it comes up before you've even drawn the layout. Get it wrong and it shows up later — a swollen sink base, screws that won't bite anymore, a painted door with every knot ghosting through six coats of top coat. Most of the time there isn't one right answer for the whole kitchen, there's a right answer for each part of it. Here's a straight answer to the questions that actually decide it, no padding, no 'it depends' where it doesn't.

Should I use plywood or MDF for the cabinet boxes?

Plywood, if the budget allows it. The layered construction means screws actually hold properly over time, which matters more than it sounds like it should. European hinges, pull-out slides, corner brackets, shelf pin holes — anything hardware-heavy does noticeably better in ply than in anything made from compressed sawdust or wood chips. MDF carcasses aren't a disaster for a dry run of wall cabinets that won't take much abuse, and plenty of fitters use them without issue. But for base units, a sink cabinet, or anything getting opened and shut daily for the next fifteen years, plywood earns its keep fast. The difference between the two only really shows up a year or two in, which is exactly why it's worth getting right now rather than finding out the hard way.

What about the doors — plywood or MDF?

Flip it round. For doors, especially painted ones, MDF usually wins. There's no grain to telegraph through the paint and no knot sitting there waiting to bleed through down the line. It also machines cleanly, so routed profiles and shaker frames come out sharp instead of fuzzy at the edges, which matters a lot once the light hits a run of doors side-on. If the client wants a stained, show-the-grain look, go hardwood plywood or a veneered MDF instead, since plain MDF won't take a clear finish well at all. For a painted shaker door, solid MDF is close to the industry default, because it holds its shape and finish better than almost anything else at that price. Plenty of working kitchens mix the two — plywood boxes, MDF painted doors — and it's not really a compromise, it's just using each material where it's strongest.

Does plywood grade actually matter under paint?

Yes, more than most people assume. A lower grade face can look fine bare in the yard, but paint is unforgiving. It sits right on the surface and shows up every patch, void, and repaired knot as a slightly different sheen or texture once it's dry and the light catches it side-on. You can usually get away with a lower grade under paint than you'd use for a stained or clear piece, since the paint film hides minor surface flaws a clear coat would expose straight away. But a rough, void-heavy face will still telegraph eventually, especially after a few seasons of humidity swings opening it back up. Spend the money on a decent face grade for anything at eye level, and save the cheap stuff for backs and unseen panels nobody's ever going to look at twice.

What do the grade letters on a plywood sheet actually mean?

• A-grade: smooth, sanded, almost no patches or knots — reserved for faces that'll be seen and finished clear.
• B-grade: solid and tight, small sound repairs allowed, fine under paint but not ideal for a clear finish.
• BB: sound, tight knots allowed, open ones get plugged with wood patches — the usual general cabinet-grade face.
• CC: rough and patched, meant for the side nobody ever sees, like the inside back of a carcass.

Combination grades like A/B or B/BB give you a good face and a cheaper back, which is exactly what you want on a cabinet side panel where only one face is ever visible. Ask your supplier for their actual grading sheet rather than guessing off the stamp, because grading isn't standardised the same way everywhere, and what one yard calls BB another might call something else entirely.

Is moisture-resistant MDF good enough for a sink base?

On its own, not really. Moisture-resistant MDF slows down water absorption, it doesn't stop it. A slow drip under a sink over a few months will still find the weak spot, usually a cut edge or an unsealed screw hole, and once MDF has properly swollen it does not go back to its original shape. It stays puffy and soft at that spot forever, no matter how long it dries out for afterwards. Plywood behaves differently under the same conditions. Good quality ply, especially with a water-resistant adhesive between the layers, can get damp and dry back out close to flat with minimal lasting damage. For the actual sink cabinet, use plywood for the base and the back panel, seal every cut edge properly, and save the MDF for places water genuinely can't reach.

Why do screws keep pulling out of MDF?

Because MDF is uniform density all the way through, with no grain or fibre direction for a screw thread to grip the way it does in real wood or in plywood's layered core. It's fine the first time you drive a screw in. It's a lot less fine the second or third time a hinge gets adjusted or a drawer slide gets re-fitted in the exact same spot. The fix is simple and most fitters already do it without thinking twice: pre-drill every hole, use screws designed for MDF or chipboard with a coarser thread, and never re-drive a screw into exactly the same hole if you can shift it even a few millimetres sideways. For anything that'll see repeated adjustment, like hinge plates or drawer runners, plywood or a solid timber block behind the MDF will hold up far better over the years.

Is plywood worth the extra cost over MDF?

For boxes, usually yes. Plywood costs more per sheet, but the difference shows up in callbacks, not on the invoice. A cabinet with pulled hinges or a swollen base six months after fitting costs you far more in remake time and goodwill than the sheet upgrade ever would have, and that's before you factor in the awkward conversation with the client about why it's happening again.

Where it's less clear-cut is anywhere low-risk and rarely touched: a filler panel, the back of a tall larder, a bulkhead infill. That's exactly where cheaper MDF, or even plain chipboard, can do the job without anyone ever knowing the difference. On a tight budget, dry room, low-wear job like a home office or a simple wardrobe, MDF throughout can be a perfectly reasonable call too. Just be upfront with the client about where it will and won't hold up long-term, so nobody's surprised later.

What thickness should I actually be using?

18mm is the standard for cabinet carcasses, sides, and shelves on most domestic kitchen jobs. It's thick enough to hold hardware properly and span a shelf without sagging under a stack of plates over time. Backs can usually drop to 12mm or even thinner if the carcass is well braced elsewhere, since the back isn't carrying the same load as the sides and base. Doors and drawer fronts commonly run 18mm as well, though some painted MDF door ranges use slightly thinner stock with a frame profile to stiffen the edges instead. Worktops are their own conversation entirely and usually start around 25mm and go up from there depending on the job.

What about melamine-faced chipboard?

Melamine-faced chipboard, usually just called MFC, is a different animal again — a chipboard core with a tough, pre-finished melamine skin bonded on top. It's cheap, comes ready-coloured or wood-effect straight off the sheet, and needs no painting or finishing at all once it's cut and edged, which is a big part of its appeal on a budget job. The trade-off shows up at the edges and in wet areas. Any cut edge exposes the raw chipboard core underneath, and that core swells with moisture faster than MDF does, so edge banding has to be done properly and sealed well on every single exposed cut. It's a solid budget option for carcasses in dry runs, but it's not the one to reach for under a sink or behind a dishwasher.

How do I stop plywood edges looking rough on a finished piece?

Plywood shows its layers the second you cut it, so a raw edge always looks and feels different from the face. Edge banding in a matching veneer, or a solid timber lipping strip, is the standard fix, and it does double duty by protecting the exposed layers from knocks and moisture at the same time. For a cleaner look on a piece that's being painted anyway, some fitters fill and sand the edge grain before priming instead of banding it. It takes longer at the bench, but it avoids a visible seam line where the banding meets the face, which matters more on anything that'll get seen up close rather than from across the room.