End grain is the face of a tree, beam or board that is cut across the fibre direction. You are effectively looking down onto a tree trunk, with the growth rings visible. The opposite face — the long face of the board — is called long grain or side grain.
What makes end grain different
Timber consists of vessels and cells running lengthwise that once carried water through the tree. On the end grain face all of those tubes are cut open. That explains nearly every property of end grain:
- It draws water like a straw. End grain absorbs moisture many times faster than long grain. That is why rot almost always starts there: the untreated end of a cladding board, a fence post or a window sill.
- It is strong in compression. A load applied along the fibres — that is, perpendicular to the end grain — is carried far better than the same load across the fibres. This is why posts, studs and columns stand on their end grain.
- It glues poorly. Adhesive soaks into the open vessels instead of forming a film. An end-grain-to-end-grain glued joint has little strength; that is what mortise and tenon joints or dowelled scarf joints are for.
- It takes stain deeply. End grain finishes darker than the surrounding face — a familiar and unwelcome effect in stained work.
Practical tips
- Prime end grain twice over. On external joinery, two extra coats of primer on every end, including the ends that will end up hidden. It is the cheapest life extension there is.
- Cut first, treat afterwards. Every cut in treated timber exposes untreated end grain. Treat that cut with a suitable end-grain preservative.
- Never stand end grain on the ground. A post foot on wet ground wicks moisture upwards. Set it on a pad, a plinth or a post base.
- End grain wears well. That is why end-grain wood block floors are laid with the cut face upwards: it is far more hard-wearing than long grain.
Related terms
- Timber
- Growth ring
- Movement in timber
- Wood rot
- Mortise and tenon joint
- Wood block floor
Want to know more about construction terms? Visit our knowledge base at fredsdiyplans.com.