Should I buy MDF or softwood skirting and architrave?

This choice is made at the merchant in about ten seconds and then lived with for twenty years. Both materials are entirely legitimate and each has one or two situations where the other is genuinely the wrong answer, so it is worth knowing which is which before you are standing in front of the rack.

Step by step

1. Choose MDF for painted mouldings in dry rooms.Living rooms, bedrooms, hallways, landings. It is straight, has no knots, no resin bleed and no grain to raise, it takes paint beautifully, it is usually cheaper, and primed lengths save a coat. For most of a house this is the sensible default.
2. Choose softwood where the finish is clear.Stained, waxed, oiled or varnished mouldings need real timber, because MDF has no grain and looks like what it is under anything transparent. Buy redwood rather than whitewood for a clear finish — it stains far more evenly.
3. Choose softwood where damp is possible.Bathrooms, utility rooms, kitchens near a dishwasher, ground floors with a history of damp, garages and conservatories. MDF skirting wicks water up from the floor at its bottom edge and swells irreversibly, and that edge is the one sitting on the floor.
4. Choose softwood where it takes wear.Hallways with bikes and pushchairs, stairs, anywhere kicked or knocked. MDF dents rather than bruising and the dent goes through the paint. Timber takes a knock better and can be filled and sanded more convincingly.
5. Match the profile before the material.In a period house, matching existing mouldings matters more than either material. Take a profile off the existing moulding with a profile gauge or a cardboard template, and check what the merchant stocks. A joinery shop will run a matching profile in softwood; MDF stock profiles are limited to the common patterns.
6. Buy long lengths for long runs.Both materials come in lengths up to 4.2 or 4.8 metres precisely so a wall can be done in one piece. A joint in the middle of a run always shows eventually, whichever material it is in.
7. Seal the cut ends of MDF.Every mitre, scribe and end cut exposes raw fibre that drinks paint and absorbs damp. Seal them as you fit, not afterwards.
8. Knot-seal softwood before priming.Resin from knots bleeds through paint, sometimes years later, and this is the main reason people end up preferring MDF. Two coats of knotting solution over every knot before the primer prevents it.

Tips

• Primed MDF saves a full coat of work and arrives with a smoother surface than you would achieve by priming it yourself. It is worth the small premium.
• MDF skirting is heavier than softwood of the same section, and long lengths flex, so a helper makes fitting long runs much easier.
• A hybrid approach works well: MDF everywhere except the bathroom, the utility room and the hall, where softwood earns its place. Nothing says the whole house has to match in material, only in profile and colour.
• MDF mouldings are usually more dimensionally consistent than softwood, so mitres close better and scribes fit more predictably. That is a real advantage for a first-time fitter.

Common mistakes

• Using MDF skirting in a bathroom or a utility room — It sits on a floor that gets wet and the bottom edge wicks water up. It swells, the paint splits along the bottom and the only fix is replacement. This is by far the most common MDF skirting failure.
• Nailing MDF architrave close to the end without a pilot hole — MDF splits along its length at an end when a nail or a screw wedges into it. Pilot everything near an end, and use a fine pin rather than a nail.
• Not knot-sealing softwood before painting — Brown patches come through the gloss months later, worst above radiators and in sunlight. Knotting solution is cheap, quick and the only reliable answer.
• Buying on price without checking the profile — A moulding that is 5mm different in height from the existing runs shows at every doorway and every point where new meets old. Match the profile first and choose the material second.

Alternatives

• Hardwood mouldings: Oak or ash skirting and architrave for a clear-finished contemporary or period look. Considerably more expensive, harder to cut and fix, and worth it where it is a feature.
• Moisture-resistant MDF mouldings: Available from some suppliers and a genuine improvement in a kitchen or utility room, though still not suitable where the bottom edge stands in water.
• Reclaimed or run-to-order softwood: The only way to match an unusual period profile exactly. A joinery shop will run a matching moulding from a template, at a price that is reasonable on a small quantity.

Questions people ask