How to price a timber frame house from plans: a 6-step method

Pricing a timber frame house comes down to the take-off. The architect's drawings give you rooms, floor areas and internal dimensions; you need wall lengths, openings, linear metres of timber per section and sheathing areas. Here is a six-step method to get from one to the other without missing anything, followed by a full worked example.

What to pull from the plan before you price

Before you count a single stud, list what the price needs. The drawings hold part of it; the rest is your own build-up, and it's worth writing it down from the start.

• Footprint and external perimeter: the length of each external wall, measured to the outside face of the frame.
• Heights: the overall wall height (not the ceiling height), number of storeys, floor zone depths.
• Load-bearing and internal walls: which ones carry the floor or roof (framed in your standard section) and which are non-load-bearing partitions, priced separately.
• Openings: width, height and sill height of every window, door and glazed opening.
• Floors and roof: type (flat roof, trussed or cut roof), span direction, intermediate supports.
• Your build-up: stud section, stud spacing (centres), number of plates (with or without a sole plate fixed to the slab under the panels, a sill plate in the US), racking sheathing. The drawings don't say: it's your standard, and it should be the same on every job.

Step 1: check the plan and list missing dimensions

Most pricing errors come from a dimension read wrongly or not there at all, not from bad arithmetic. Spend five minutes checking the plan:

• do the running dimensions along each elevation add up to the overall dimension?
• are they internal (room) or external (structure) dimensions? For the frame, you need the outside face of the walls;
• does every window have a height and a sill height? Planning drawings rarely show them;
• does the drawn wall thickness match your build-up (frame, insulation, linings)?
• for an image or a scan, can you check the scale against a known dimension?

Each missing dimension should become either a question to the client or an assumption written on the quote. A "standard" value slipped in without saying so is a gap you'll find on the shop floor.

Step 2: wall take-off

Work wall by wall, in the same order on every job (clockwise from the front door, for instance). For each wall, note the length, the overall height, the gross area (length × height), then the net area (gross area minus openings).

For the frame, the number of common studs in a wall is its length divided by the stud spacing, rounded up, plus one. On an 8.00 m wall at 600 mm centres: 8.00 / 0.60 = 13.33, rounded up to 14, plus 1, so 15 studs. Then add the corner studs, the studs at internal wall junctions and the studs either side of each opening. The full counting method is in our timber frame wall take-off guide.

In the US, the same rule applies with 2×4 or 2×6 studs at 16 or 24 in. on centre (o.c.): a 26 ft wall at 16 in. o.c. gives 26 × 12 / 16 = 19.5, rounded up to 20, plus 1, so 21 studs.

Keep a sanity-check ratio: linear metres of framing timber per m² of gross wall. In the example below, it comes to about 3.6 lin. m of 45 × 145 per m² of external wall. Work out your own from your last few jobs: it doesn't replace the take-off, but it catches a gross error in ten seconds.

Step 3: openings and their framing

An opening takes area away from the sheathing, but it adds framing timber. For each opening, count:

• two full-height studs, one on each side;
• two cripple studs (jack studs in the US) under the lintel;
• one lintel (header), often two plies for short spans;
• for a window, a sill and short studs under the sill, in place of the common studs that were cut.

Large glazed openings fall outside any ratio: their lintel has to be designed (often glulam or LVL) and priced separately, once your engineer has sized it.

Step 4: floors and roof

For a joisted floor or flat roof, the rule is the same as for walls: number of joists per bay = length to cover / joist spacing, rounded up, plus one. A joist is the span plus its bearings. Add rim joists, trimmers around openings and noggings or blocking if your detail calls for them.

For a cut roof or trussed rafters, price it the way you usually do; just make sure you don't count it twice with the ceiling joists.

Step 5: sheathing and membranes

Racking sheathing, breather membrane, vapour control layer and insulation are priced on the net wall area, plus a waste allowance. The number of boards depends on your board layout: a 2.50 m high wall in 2.50 × 1.25 m boards doesn't produce the same offcuts as a 2.70 m wall.

Step 6: from quantities to a price

Once the quantities are out, the price is built in four blocks:

1. Materials: linear metres converted to m³ (length × section) and multiplied by your price per m³; boards and membranes per m²; fixings and connectors.
2. Factory or shop labour: your hours per m² of wall or per panel, measured on past jobs.
3. Site erection: crew, duration, crane.
4. Transport, overheads and margin.

Your ratios are what make the price right. The take-off itself must be exact and repeatable: it's the part you can get straight from the drawings.

Worked example: a 96 m² single-storey house

Assumptions. Rectangular house, 12.00 × 8.00 m (external dimensions), 2.50 m walls, 45 × 145 mm studs (close to a US 2×6) at 600 mm centres, one bottom plate and a double top plate (studs 2.365 m long). Six 1.20 × 1.25 m windows (0.95 m sill height), one 0.90 × 2.20 m front door, one 2.40 × 2.20 m glazed opening. One load-bearing internal wall down the middle, counted as 12.00 m for simplicity (it is 11.71 m between the inside faces of the external walls), with two 0.90 × 2.20 m doors. Flat roof: 45 × 220 joists at 600 mm, in two 4.00 m spans bearing on the internal wall.

The quantities

The net timber weighs about 2.1 t, based on the mean density of C24 softwood (420 kg/m³ in EN 338). US lumber species differ: use your supplier's figure.

From quantities to a price: the build-up

Each line of the price starts from a quantity in the table, multiplied by your buying price or your labour rate:

The factory hours come from two example ratios: 0.8 h per m² of gross wall (130 m² of external and internal load-bearing walls) and 0.4 h per m² of roof (96 m²). This build-up covers the frame package only: no insulation, windows, roofing membrane, flat roof falls or foundations.

What matters in this example is traceability: every line of the price points back to a quantity, and every quantity to a written assumption. If the client changes a window, you know exactly which lines move.

Common mistakes

1. Pricing per m² of floor area with a single ratio. An L-shaped house or one with large glazed openings doesn't have the same ratio as a rectangle.
2. Deducting openings from the framing timber. They reduce sheathing areas, but add studs, cripple studs and lintels.
3. Forgetting corners and internal wall junctions. A few studs per wall, but across a whole house it shows.
4. Mixing up ceiling height and wall height. The floor zone and the plates change the stud length.
5. Filling in a missing dimension without writing it down. The assumption belongs on the quote.
6. Ignoring waste and stock lengths. Timber is bought in stock lengths, not by the exact metre.
7. Redrawing the whole project once you win it. If the take-off comes from a model, that model should feed production. Going from floor plan to 3D model at the pricing stage gives you that model.

References

• EN 1995-1-1 (BS EN 1995-1-1 in the UK), Eurocode 5: Design of timber structures, Part 1-1: General, Common rules and rules for buildings: the design standard behind the sections and stud spacing you count. Overview on the European Commission's Eurocode 5 page.
• NHBC Standards, chapter 6.2, External timber framed walls: NHBC's technical requirements for the external walls of timber framed homes in the UK.