Naming the timber nobody looks up at.
A single vertical post rising from the centre of the tie beam to the ridge, with two struts angling down to meet the principal rafters partway along. The simplest truss capable of a wide span, and the one drawn above. Common in parish naves rebuilt cheaply after the Reformation.
Two vertical posts, set either side of centre, carrying a horizontal collar between them instead of a single post to the ridge. Gives a wider clear space above the collar, useful where a rood loft or later ceiling needed the room.
No tie beam crosses the full span at all. Short horizontal hammerbeams project from the wall, each carrying a hammer post that rises to meet an arch brace, so the whole load is carried on brackets rather than a beam stretching wall to wall. The showpiece truss — Westminster Hall is the type example, but plenty of parish churches have a modest version.
Paired rafters that cross each other diagonally rather than meeting only at the ridge, braced where they cross. Gives a pointed, almost vaulted look from below with no horizontal tie visible at all.
A collar beam set high, with curved braces sweeping down from it to the wall posts, reading from below as a continuous arch. Often the roof chosen where the building committee wanted something that looked like stone vaulting without paying for stone.
| Mark | Member | Typical section |
|---|---|---|
| A | Tie beam | 300 × 250mm oak |
| B | Principal rafter | 200 × 150mm oak |
| C | King or queen post | 180 × 180mm oak |
| D | Purlin | 150 × 120mm oak or elm |
| E | Wall plate | 150 × 100mm, often elm for its rot resistance |
East Anglian roofs lean hard on the hammerbeam, often doubled into two tiers with carved angels at the beam ends — timber was dear on the fen edge and the design let a builder use shorter, cheaper lengths. In the West Country, wagon roofs with close-set rafters and boarded ceilings hide their trusses almost entirely, favouring a smooth barrelled underside over visible carpentry. Welsh border churches tend toward the arch braced collar, likely following the same masons and carpenters who worked the great houses nearby. Northern roofs, exposed to heavier snow load, keep trusses closer together and members noticeably thicker for the same span.