Why are fitted cabinets not made from solid wood?

Because solid timber moves with humidity. A two metre wardrobe door made from solid boards will cup or split as conditions change, and a room cooled intermittently swings more than one held steady. Sheet materials stay flat, which is the reason they exist. Solid timber still belongs in frames, edges and anywhere narrow enough to move safely.

Which is better for a kitchen?

Plywood for the carcass generally, because it holds screws and hinges better and tolerates moisture more than MDF does. For painted doors, MDF gives a cleaner surface and a crisper machined edge. The mistake to avoid is chipboard anywhere near water, since it swells once moisture reaches it and does not recover.

Is MDF a cheap material?

It is the correct choice for specific jobs rather than a compromise. Nothing takes paint better, because it is uniform throughout with no grain to raise and no voids at the cut face, which is why painted doors and moulded profiles are made from it. Its weaknesses are weight, poor screw holding at the edge, and no tolerance for standing water.

How do I find out what my cabinets are made of?

Ask for the specification in writing in the quotation, by name rather than by adjective. If you can see an uncovered cut edge, MDF looks uniform with no layers, plywood shows its plies clearly, and chipboard shows coarse flakes. If the quotation does not state the material, that is itself the answer.

MDF or plywood, and which belongs in your cabinets

Fitted joinery is almost never solid timber, and it should not be. The real question is which board, and where.

Nearly all fitted joinery is built from engineered boards, and that is an engineering decision rather than a compromise on quality. Solid timber moves with the humidity around it. Sheet materials move far less, which is what keeps doors straight and shelves flat.

So the question is not solid against engineered. It is which board, and where in the cabinet.

MDF

What it is. Fine wood fibres compressed with resin under heat and pressure, producing a board that is uniform all the way through with no grain direction and no knots.

Where it wins. Paint. Because there is nothing in it to interrupt the surface, it machines to a clean edge, takes a moulded profile crisply, and finishes flat with no structure showing through. Painted doors and anything with a shaped edge belong here.

Where it does not. It is heavy. It holds screws poorly at the edge unless the fixing is designed for it. And it swells if water sits against it, so an exposed MDF edge under a sink is a problem waiting for its moment.

Plywood

What it is. Thin layers of timber glued with the grain of each layer running across the one below. That cross-banding is where its strength and stability come from.

Where it wins. Structure. Anything carrying load, anything with hinges opening daily, anything in a damp environment. It holds a fixing noticeably better than MDF and it is lighter for its strength.

Where it does not. The edge shows its plies, so it is either covered with edge banding or treated as part of the design. It is also less ideal under a high gloss paint, because the timber structure can telegraph through.

Chipboard

Flakes and particles pressed together. It is the cheapest of the three and the weakest, and it appears in budget flat-pack furniture and in work priced to the minimum.

Its problem is water. Once moisture gets in it swells, does not recover, and loses its grip on fixings. In a kitchen or a bathroom that becomes a question of when rather than whether.

The visible surface is a separate decision

Veneer is real timber sliced thin over a stable core, so you get genuine grain without genuine movement. It can be sanded and refinished once or twice with care, since there is little thickness to lose.

Laminate and HPL are printed and considerably harder wearing, and they will not refinish at all.

Melamine is the usual surface for internal carcasses. Practical, inexpensive and perfectly acceptable where it is not seen.

None of these is better in the abstract. A veneered door in a formal room with melamine carcasses inside the same wardrobe is a sensible, ordinary specification.

What a good cabinet specification looks like

Plywood or a high density board for the carcass. MDF doors if they are painted, veneer if the timber is meant to show. Edges properly banded, especially anywhere damp. And hinges and drawer runners named by manufacturer.

That last item is where a quotation gets quietly cheapened. A hinge is opened thousands of times, and replacing it later is harder than changing anything else in the cabinet.

The point everyone forgets

The wall is never straight. Fitted work is scribed to the wall it meets, which is why it is measured on site after the plaster rather than taken off a drawing. Units ordered to drawing dimensions and delivered into a real room are where the gaps that everyone notices afterwards come from.

There is more on how this is handled on the joinery page.

Questions

Questions we get asked

Why are fitted cabinets not made from solid wood?: Because solid timber moves with humidity. A two metre wardrobe door made from solid boards will cup or split as conditions change, and a room cooled intermittently swings more than one held steady. Sheet materials stay flat, which is the reason they exist. Solid timber still belongs in frames, edges and anywhere narrow enough to move safely.
Which is better for a kitchen?: Plywood for the carcass generally, because it holds screws and hinges better and tolerates moisture more than MDF does. For painted doors, MDF gives a cleaner surface and a crisper machined edge. The mistake to avoid is chipboard anywhere near water, since it swells once moisture reaches it and does not recover.
Is MDF a cheap material?: It is the correct choice for specific jobs rather than a compromise. Nothing takes paint better, because it is uniform throughout with no grain to raise and no voids at the cut face, which is why painted doors and moulded profiles are made from it. Its weaknesses are weight, poor screw holding at the edge, and no tolerance for standing water.
How do I find out what my cabinets are made of?: Ask for the specification in writing in the quotation, by name rather than by adjective. If you can see an uncovered cut edge, MDF looks uniform with no layers, plywood shows its plies clearly, and chipboard shows coarse flakes. If the quotation does not state the material, that is itself the answer.

MDF