Set out a block
Put the plan on the ground with cord, pegs and a triangle: square corners, straight lines and levels anyone can check again.
Home: Settlement and planning, Level 2 · Forge, level 3 of 7 in its track. Serves 1 step.
Every build on this site has hazards that injure or kill — quicklime, carbon monoxide, molten metal, collapsing ground. Read the safety notice before starting, and read this build's own failure modes below.
What it is and why this shape
A plan on paper protects no one until it is on the ground. Plots out of square, streets that narrow and building lines that drift a metre along a block turn into boundary disputes and streets that can never be widened. Everything here uses tools a group can make: a cord knotted every metre, pegs, boards and the 3-4-5 triangle, which gives a right angle by counting alone, because 3² + 4² = 5².
Setting out a foundation, in plan
Fig 1
Timber
Specifications
| Plot module | 10 × 30 m | As in plot, street and block; any module works if it is repeated. |
| Main street | 6 m or more | Between building lines. |
| Rear lane | 3 m or more | For waste, fuel and animals. |
| Right angle | 3-4-5, or 6-8-10 | The larger triangle halves the error of a stretched cord. |
| Diagonals | equal | For a 6 × 8 m rectangle, 10 m each. |
| Board setback | 1–1.5 m | Outside the corners, clear of the digging. |
Bill of materials
| Material | Quantity | Notes and substitutes |
|---|---|---|
| Cord, non-stretch | 2 × 50 m | Knot or tie a coloured thread every metre, and check it against a known length before each day's work. |
| Pegs | about 60 | Hardwood, 40–50 cm long, pointed; one per plot corner plus spares. |
| Board stakes and cross-boards | 4 per building corner | Two stakes and one board each side of a corner. |
| Nails | a handful | Driven into the tops of the boards to hold the strings. |
| Water level | 1 | A clear tube of water, as in irrigation, for levels and falls. |
| Mallet, saw, and lime or ash | — | Lime or ash to mark lines on the ground. |
Tools: Knotted cord · Mallet · Saw · Water level · Plumb bob · A second cord for the 3-4-5 triangle
Construction
Fix a baseline
Choose one straight line you can see from end to end, usually the front building line of the main street, and drive a peg at each end. Everything else is measured from this line, so check it twice: sight along the pegs, and measure its length with the cord in both directions.
Square the first corner with 3-4-5
From the corner peg, measure 4 m along the baseline and peg it. From the corner, swing a cord 3 m long, and from the 4 m peg a cord 5 m long; where they meet is the square corner. Use 6-8-10 on larger layouts: the same angle, with half the error.
Peg the plot corners along the line
Measure along the baseline and peg every plot corner at the module width, 10 m for the standard plot, measuring each from the baseline's end peg rather than from the last peg, so errors do not add up. Number each peg as you drive it.
Check the diagonals
For every rectangle, a plot or a building, measure both diagonals: they must be equal. For a 6 × 8 m building each is 10 m. If one is longer, move the far corners along their sides until the two agree.
Put up batter boards for anything you will dig
Where a building or a drain will be dug, set batter boards 1–1.5 m outside each corner: two stakes and a cross-board on each side. Stretch string lines between nails on the boards so the strings cross exactly over the corner pegs (check with a plumb bob). The pegs will be dug out; the strings on the boards put the corners back at any time.
Set the levels and falls
With the water level, mark the same height on every board for floors, and for drains mark the fall: at 1 in 100 a drain drops 10 cm every 10 m. Floors go above the flood line recorded when the site was chosen.
Replace the pegs with lasting corners
When the plots are agreed, replace each corner peg with a buried stone or post, record its number and position in the property record, and keep the baseline pegs as the reference for re-measuring.
Tolerances that matter
| Dimension | Target | Why it matters |
|---|---|---|
| Plot frontage | ±5 cm over 10 m | Smaller than a wall's thickness, so neighbours' walls never cross the line. |
| Building diagonals | equal within 1 cm for a house | Out of square carries into every wall, the roof and the floor. |
| Street width | never less than planned | A street can be built narrower by accident and is never widened afterwards. |
How this fails
Measuring each plot from the last peg. The errors add up, and the last plot in a block comes out a metre short. Measure every corner from the baseline.
A stretching cord. A natural-fibre cord gains length when wet and when pulled; check it against a fixed length every day.
Pegs used as the only mark. They are knocked out during digging. Batter boards outside the work keep the lines.
Skipping the diagonals. A rectangle can have four right-looking corners and still be out of square.
How you know it worked
VerificationEvery plot measures its module to within 5 cm, both diagonals of every building agree, the main street is at least 6 m wide along its whole length, and the corner stones match the numbers in the property record.
Scaling and variants
One house: four batter boards and two strings. A block: one baseline per street and every corner measured from it. A town: a surveyed grid with permanent reference stones at street crossings, from which every block is set out.