Making a Wooden Ladder — Rung Mortises and Wedged Tenons

A wooden ladder is one of the most essential structures in any building project — and one of the most dangerous if poorly made. A rung ladder consists of two long poles (the stiles) with a series of horizontal rungs mortised through them. Every rung is a structural beam carrying the full weight of the climber, and every joint must hold under dynamic loading — the shock of a foot landing on a rung is several times the climber's static weight.

The stiles must be straight-grained poles, ideally from a naturally straight tree like ash, spruce, or larch. Ash is the traditional choice — strong, flexible, and light for its strength. The rungs are short pieces of hard, dense wood — oak or beech — with tenons that pass through the stile and are wedged on the far side. The wedge locks the rung permanently and prevents the joint from working loose under repeated loading.

A well-made wooden ladder lasts for decades and has one advantage over metal: it does not conduct electricity. For this reason, wooden ladders remain in use by electricians even today. The technique described here — through-mortised, wedged rungs — is the strongest form of ladder construction and has been used unchanged since at least the Bronze Age.