What is the difference between MDF, plywood and chipboard?
Three boards that look interchangeable in a merchant and behave completely differently once wet or loaded.
- Difficulty
- beginner
- Time
- 15 min
- Read
- 2 min
- Safety
- warning
Short answer
MDF for painted indoor work with a smooth finish, plywood for anything structural or that might get damp, chipboard only where it will be covered and stay dry. Water is what separates them — MDF and chipboard swell irreversibly.
These three are stacked next to each other at similar prices and are not substitutes. Choosing on price alone is why shelves sag and bathroom cabinets swell at the bottom.
Safety
Step by step
- Use MDF for smooth painted work indoors.No grain, no knots, perfectly flat, and it takes paint beautifully. Ideal for shelving in dry rooms, panelling, and anything that will be painted rather than stained.
- Know MDF's weaknesses.It swells permanently if it gets wet, sags under load over long spans, and edges need sealing or filling before painting because they drink paint. Screws into the edge split it unless pilot-drilled.
- Use plywood where strength or moisture is involved.Cross-laminated layers make it strong in both directions and far more stable. It holds screws well, including in the edge, and marine or exterior grades tolerate damp.
- Check the plywood grade.Grades describe the face quality and the glue. Interior-grade glue fails in damp; exterior and marine grades do not. Birch ply has a much better edge than softwood ply if it will be visible.
- Use chipboard only where it stays dry and covered.Cheapest and weakest. It is what most flat-pack furniture and floor decking is made from. It swells dramatically when wet and never recovers.
- Consider moisture-resistant versions carefully.Green-tinted moisture-resistant MDF and chipboard tolerate humidity better. They are not waterproof, and they are not suitable for anything that will actually get wet.
- Think about the span if it will hold weight.MDF and chipboard sag over long unsupported spans, particularly with books. Plywood is considerably stiffer. Add supports or use a thicker board rather than a longer one.
- Plan the edges.MDF edges need sealing and filling. Plywood edges show the layers, which some people like and others cover with edging strip or a solid timber lipping.
Tips
- Most merchants cut sheets to size, often free or very cheaply. It is more accurate than cutting a full sheet at home and far easier to transport.
- Sheet materials are heavy and awkward. A full sheet of 18mm MDF is a two-person lift.
- For a bathroom or utility, use exterior-grade plywood rather than moisture-resistant MDF. The extra cost is small against replacing a swollen unit.
Questions people ask
Can I use MDF in a bathroom?
Not where it may get wet. Moisture-resistant MDF tolerates humidity but not water, and ordinary MDF swells permanently. Exterior-grade plywood is the safer choice.
Which is strongest?
Plywood, by a clear margin, because of the cross-laminated layers. MDF is flat and smooth but sags under load; chipboard is the weakest of the three.