How do I pick straight, sound timber at the merchant?

Merchant timber is not sorted for you. A pack contains boards of genuinely different quality at the same price, and picking through takes minutes and saves hours. This is the single highest-value habit in buying timber, and most people never do it because they assume they are not allowed to.

What you'll need

• A few minutes and the willingness to move boards
• A tape measure
• A moisture meter, if the job is joinery

Step by step

1. Ask where you may sort, and put the pack back tidily.In a trade counter yard the answer is almost always yes. Restack what you reject neatly rather than leaving a heap — that is the whole social contract and it means you are welcome to do it again.
2. Sight down each face for bow.Stand the board on end, close one eye, and look down the length of the wide face. A curve along the length seen this way is bow. Mild bow is workable — it can be pulled out by fixings or removed by cutting the board shorter — so it is a reason to prefer another board, not always to reject.
3. Sight down each edge for spring.Same thing looking down the narrow edge. A curve here is spring, or crook. It matters most where the edge has to be straight — a stud, a shelf front, a door stile — and it is much harder to pull out than bow.
4. Look at the end for cup.A curve across the width. It often relaxes if the board is restacked with air on both faces, so it is the most forgivable of the four distortions, but a badly cupped wide board is still a poor buy.
5. Check for twist, and reject it.Rest the board on a flat surface and see whether all four corners touch, or sight down it and see whether the far end is rotated relative to the near end. Twist is the one to put back every time: it does not recover, and it fights you at every stage of the job.
6. Judge the knots.A live knot, tight and with the grain flowing round it, is fine in most work. A dead or encased knot, ringed with dark bark, will loosen and fall out. Reject any board with a large dead knot where it matters, and any knot on the edge of a piece that will be structural.
7. Check the arrises for wane.Wane is a rounded corner where the board included the outside of the log, sometimes with bark still on. It means you are not getting the full section, and it is a problem anywhere something has to be fixed at that corner or the full width is being relied on.
8. Look for splits, shakes and end checks.Short splits running in from the ends are extremely common, usually shallow, and simply cut off — allow for the loss in your length. A shake running along the grain in the middle of a board is a different matter and is a reject.
9. Feel for wetness and look for staining.Cold, heavy and damp means it will shrink after you fit it. Diffuse blue-grey staining is sapstain, which is cosmetic. Soft, crumbly or spongy timber, or dark patches that dent under a thumbnail, is decay and goes straight back.
10. Buy all the matching pieces at once, from one pack.Sizes and colour vary between batches. If several pieces have to line up or match visually, take them all from the same bundle in the same visit.
11. Buy a little extra.One length more than the cutting list needs costs a few pounds and covers a split you did not see, a cut in the wrong place and the fact that you will lose the ends of some boards to checks.

Tips

• Go at a quiet time. First thing on a weekday morning at a trade counter, you can sort a whole pack in peace; on a Saturday at a DIY shed you cannot.
• If the good boards are all at the bottom of the rack, they are at the bottom because everyone else sorted from the top. It is worth digging.
• For a large order, ask whether you can select from the pack before it is loaded — many yards will let you, and it is far easier than rejecting on delivery.
• Carry a short offcut of known thickness as a gauge if you are matching an existing size. Comparing beats measuring for spotting a batch that is a millimetre out.

Common mistakes

• Taking the top boards because they are easiest to reach — The top of a pack has dried fastest, been rained on, and been picked over. It routinely contains the worst boards in the bundle.
• Only checking the face and not the edge — A board can be dead straight on the face and sprung badly on the edge. Both need sighting, and it takes an extra two seconds each.
• Rejecting every board with a knot — Knots are normal in softwood and most of them are harmless. What matters is whether they are live or dead, how big they are relative to the section, and whether they are at the edge of a piece that will carry load.

Questions people ask