Most weeks somebody asks me why our quote is more than the other shop's. Or — same question, different angle — why we charge what we charge. The cabinet boxes are usually most of the answer. The cabinet boxes are usually plywood. The other shop's are MDF.
I don't hate MDF. I have a stack of it in the corner of the shop, against the back wall, behind the table saw. I use it. I just don't use it where it counts.
What MDF actually is
Medium-density fiberboard. Wood fibers and resin, pressed into sheets at high temperature. Cuts smooth, paints well, costs about half what cabinet-grade plywood costs. For paint-grade work, in the right application, it's a reasonable material. It also has problems people don't talk about until they've been bitten.
Where it fails
Moisture. A drop of water sitting on a cut MDF edge for an hour will swell the edge a sixteenth of an inch. It doesn't shrink back. The kitchen sink cabinet you had built out of MDF in 1998 is not the kitchen sink cabinet you have now. That's not opinion — that's chemistry.
Fasteners. Screws into MDF hold for a while. Then they don't. The fibers around the threads pulverize over time, especially if anything gets repeatedly fastened and unfastened. Cabinet hinges loosen. Drawer slides start to wobble. Five years in a busy kitchen, you'll start seeing it.
Edges. A cut MDF edge looks fine sealed and painted. After ten years of someone's kid kicking the bottom rail of a built-in, the edge doesn't look fine anymore. Plywood takes the impact. MDF doesn't. The fibers break apart. You can fix it. You'll fix it again.
Where I will use it
- Painted built-in shelves, where the load isn't structural and nothing's touching the edges. MDF takes paint better than plywood does — no grain telegraphing through, no patching needed.
- Crown molding for paint-grade work. Long sections of MDF crown are dimensionally stable, won't twist, take paint without the prep poplar needs. I'd use it in any colonial revival job that's painted-trim.
- Paint-grade trim profiles in low-traffic areas. Picture rails, chair rails. Not base trim — base trim gets vacuum cleaners and dog tails.
- Templates and jigs. Half my shop jigs are MDF. It's flat, stable, cheap. Doesn't matter if I cut it up.
Where I won't
- Cabinet boxes for any kitchen, stained or painted. Plywood, every time. Birch ply for paint-grade, white oak ply for stain-grade.
- Drawer boxes. Solid wood, nothing else.
- Anything that touches water on purpose — sink cabinets, vanities, mudroom benches.
- Built-in shelving where the shelves get loaded heavy. Books, especially. MDF shelves bow under a row of hardcovers within six months.
- Anything I want to be there in fifty years.
The fight isn't with MDF. The fight is with shops that quote MDF cabinet boxes for stain-grade kitchens because it makes the bid look better.
What this costs you
Cabinet-grade plywood costs about double what MDF costs. On a kitchen, that's maybe $1,200 in materials. Four hundred dollars a year over a kitchen's expected life. Less than what people spend on coffee subscriptions. Worth it.
The math is simple. The fight isn't with MDF. The fight is with shops that quote MDF cabinet boxes for stain-grade kitchens because it makes the bid look better. The clients don't know to ask. The shops don't volunteer.
Now you know to ask. So ask.