Which wood should I use for a job?
Softwood or hardwood, treated or untreated, and the sizing convention that catches everyone out.
- Difficulty
- beginner
- Time
- 20 min
- Read
- 2 min
Short answer
Softwood for most jobs, hardwood where it will be seen or take wear, and pressure-treated for anything outdoors touching the ground. And remember timber is sold by nominal size — a 4x2 is not four inches by two.
Timber choice is mostly about where it lives and what touches it. The one thing that catches everyone the first time is that the size on the label is not the size of the wood.
Step by step
- Understand nominal versus actual size.Timber is named by its sawn size and sold planed, so it is smaller than the label. A nominal 4x2 is typically around 95x45mm. Measure before designing anything to fit.
- Use softwood for most structural and hidden work.Pine and spruce. Cheap, light, easy to cut and screw. Studwork, framing, battens, shelving that will be painted. It dents easily, which matters only where it is seen.
- Use hardwood where it shows or takes wear.Oak, ash, beech. Considerably more expensive, much harder wearing, and worth it for worktops, stair treads, furniture and anything with a visible grain.
- Use pressure-treated timber outdoors.Green or brown tinted, treated to resist rot. Essential for anything in contact with the ground — fence posts, decking joists, raised beds. Untreated softwood outdoors rots within a few years.
- Seal any cut ends of treated timber.The treatment penetrates from the outside, so a cut exposes untreated wood. End-grain preservative on every cut is a small step that makes a large difference.
- Check it is straight before buying.Sight down each length. Warped, twisted and bowed timber is common in merchant stacks and it makes everything afterwards harder. Pick through the pile.
- Check the moisture content for indoor work.Timber shrinks as it dries. Wood bought wet and used indoors will shrink, opening joints. Kiln-dried is worth it for anything precise.
- Match the grade to the job.Structural grades are marked and matter for anything load-bearing. For a shelf it is irrelevant; for a joist it is not, and building control will ask.
Tips
- Buy timber a few days before you need it and store it flat indoors. It acclimatises and any warping shows before you have cut it.
- Reclaimed timber is often better quality than new, particularly older softwood, which is denser and slower grown.
- Redwood and whitewood are both softwoods sold interchangeably. Redwood is more durable and takes finishes better.
Questions people ask
Why is a 4x2 not four inches by two?
Timber is named by its sawn size and sold planed, which removes several millimetres from each face. A nominal 4x2 is typically about 95x45mm — measure before designing.
Do I need treated timber outdoors?
For anything in ground contact or permanently exposed, yes. Untreated softwood rots within a few years, and cut ends need sealing with end-grain preservative.