Interactive lesson

Timber framing, step by step

Interactive lesson: which wood for what, seasoning timber, protection without poisons, sizes for beams and rafters, joints, bracing and checking old timber.

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The whole lesson as text

1. Timber as a building material

Old barns and granaries last for centuries, built from ordinary timber from the nearby woods.

Wood for the ground — Only black locust (robinia), oak heartwood or sweet chestnut goes in the ground. Locust lasts 20–30 years in the ground.
Spruce and pine under a roof — Spruce, fir and pine are for beams, rafters and battens under a roof. Outdoors only with design protection or treated.
Boxed heart — Ask the sawmill for spruce and pine beams free of heart (pith), because the heart splits as it dries. Oak is the other way round: the heartwood is the most durable, so cut off the sapwood.
Check every beam — For a load-bearing part don't take a beam with a large knot on the edge, sloping grain, a split through the thickness, rot or a strong bow.

Why: They last because the timber is dry, doesn't touch the ground and has a roof with an overhang. A new lean-to of treated spruce, posts concreted into the ground and no overhang, can rot in ten years.

Beech rots outdoors in 2–3 years. Poplar and willow are only for temporary things and under cover.
A rural sawmill often has no grade stamp (such as C24, or No. 2 in the US). Then choose yourself and go up a size.

2. Moisture and seasoning

Freshly felled wood holds 50–100 % moisture, and as it dries it shrinks.

Moisture up to 20 % — For framing, timber at up to 20 % moisture. Measure with a pin meter in the middle of a board, not at the end.
Base and gaps — A level base 30–40 cm off the ground. In each layer leave 2–3 cm gaps between pieces.
Stickers one above the other — Dry stickers of equal thickness (2–2.5 cm) every 50–60 cm, exactly one above the other. Otherwise the timber bends.
Roof, weight, label — A roof of metal sheet or boards, sides open. Weight on top so the top layers don't twist, and a label on the end: species, date, size.

Why: Across the grain it shrinks by up to 8 %, along it almost nothing. A beam built in green dries in the frame, twists, splits and loosens the joints.

The old carpenters' rule: a year per inch (2.5 cm) of thickness. A 10 × 10 cm beam is ready to build with after two or three years.
Seal the ends of oak and chestnut with wax, paint or wood glue so they don't split.