What sawn timber is
Sawn timber is everything that comes out of the round log at the sawmill. The log is cut, and depending on the section the result takes a different name. Squared timber starts at 60 mm width with a depth at least equal to the width. A plank is at least 40 mm thick and more than twice as wide. A board sits between 8 and 40 mm thick at 80 to 300 mm wide. A batten stays under 40 mm wide and 80 mm deep.
The second distinction is the edges. Edged timber has parallel sawn long edges with no wane — the same dimension throughout. On waney-edged material the natural line of the trunk remains, bark included; the width changes along the length.
Sawn timber is normally supplied rough sawn and traded green, air dried or kiln dried. It is raw material — what becomes of it is decided further down the line.
Advantages
- Inexpensive. No planing, no drying, no gluing — the shortest route from log to material.
- Any species. Whatever the forest yields can be cut. Softwood and hardwood, native and imported.
- Free dimensions. The cut follows the requirement, not a catalogue.
- No adhesive. Pure solid timber, cleanly separable at end of life and unproblematic for building-biology requirements.
- Waney edge saves material and gives table tops and cladding a look that planed stock cannot reproduce.
- Readily available, because standard sizes move in volume.
Drawbacks
- The timber keeps moving. Undried sawn timber shrinks, cracks and twists once installed. Anyone needing dimensional stability is in the wrong place.
- Coarse tolerances. Rough sawn means rough sawn — dimensional variation and rough surfaces are part of it.
- Not calculable without strength grading. For load-bearing components the basis is missing as long as no strength class is assigned.
- Waste with waney-edged stock. The wane has to go once a straight dimension is needed — usable yield is well below the volume purchased.
- Bark is a risk. Insects and moisture sit on the waney edge; it has no place in interior fit-out.
- Reworking required where smooth surfaces or chamfered edges are specified.
Applications
- Sheathing, roof battens and counter battens
- Substructures and temporary works on site
- Packaging and pallet construction
- Fences, screens, simple garden structures
- Rustic cladding and exposed ceiling boarding
- Waney-edged planks for table tops, counters and furniture with a live edge
- Raw material for further processing in the joinery shop
Where to avoid sawn timber
- Load-bearing components without grading. Rafters, studs and joists need a proven strength class — that is what structural timber is for.
- Exposed components with dimensional demands. Where joint lines and edges must be right, planed and dried stock is the better choice.
- Heated interiors with green timber. Anything installed at high moisture content will move considerably over the first winter.
- Weather-exposed structures in non-durable species. Spruce outdoors does not last without protection.
- Ground contact. Without a suitable species and proper detailing that is an expiry date, not a component.