Problems

What fails in a joint, and how to read the failure.

• SplittingWood breaking apart along the length of its grain rather than cut cleanly across it, done on purpose to convert logs and guarded against elsewhere.
• WarpingWood losing its flat, straight shape as its moisture changes, twisting along its length, cupping across its width or bowing along its face.
• RackingThe tendency of a frame or joint to distort out of square under a sideways load, leaning like a parallelogram instead of holding its right angles.
• Wood movementHow solid wood swells with moisture and shrinks as it dries, unevenly by direction, which can break a joint or split the work if ignored.
• KnotsThe base of a branch preserved in the surrounding trunk wood, where the grain changes direction around it and always leaves a weak point.
• Wet rotDecay caused by fungi that need moisture to grow, consuming the cellulose that gives wood its strength rather than just colouring or coating it.
• BruisingDamage done to wood by crushing rather than cutting, leaving a dent or patch of crushed fibre where something pressed too hard on the surface.
• ShakesA crack opening inside a piece of timber along the grain, usually following the growth rings, most often as the wood dries and shrinks.
• Proud jointA joint or part standing a little higher than the surface around it, either deliberate and left for trimming or an unwanted fault to correct.
• Tear-outA cutting edge failing to sever wood fibres cleanly and ripping a ragged torn hollow instead, with different causes and fixes in different situations.
• Dry rotFungal decay in felled timber, driven mainly by dampness and poor air circulation despite its misleading name.
• FoxinessA reddish or yellowish brown stain appearing in timber's grain when fungal decay is just beginning, before the wood softens or loses strength.
• Gaps in jointsAn opening where a joint's mating surfaces no longer meet, leaving the connection loose or visibly open.
• WoodwormThe common name for holes and damage made when beetle larvae tunnel through timber.
• Case hardeningA drying defect where the outer part of wood becomes drier and harder while the interior stays wetter, leaving stress between the case and the core.
• Glue failureThe loss of a bonded connection between pieces of wood, often leaving the joint weaker than the wood it was meant to hold together.