Mill & MerchantLearn · Plan · Build

Project tools

Shed & Outbuilding Planner

Step-by-step style shed planner logic ported from the mockup to produce practical framing and cladding quantities.

Start with footprint & height. You are ordering counts of studs & plate metres for a rectangular shell—roof, doors & lintels intentionally simplified out.

Quick start

  1. Type external footprint width × depth plus wall plate height—all millimetres (inside face rough assumption).
  2. Stud spacing presets common UK multiples (450/600). Tighter spacing stiffer walls & more studs.
  3. Waste boosts material for cross-cuts—you can zero it pessimistically if machining exact.
  4. Read materials panel as planning quantities—you still pick lengths at merchant multiples.

What each thing means

Width / depth
Outer rectangle plan dimensions; tool assumes orthogonal corners & single-storey loop—no overlaps for partitions.
Wall height
Stud height excluding sole plate doubling—assume plates included separately in metre tally logic.
Stud spacing
Centres increment stud count perimeter formula—changing spacing adjusts both runs along each wall independently.
Waste %
Multiplies studs & cladding area fudge—helps small builds where offcuts spoil efficiency.

Dimensions & structure

External rectangle only—subtract doors/windows from cladding mentally for now.

Material summary

20 studs

19 linear metres of sole/head plates

Estimated cladding coverage

19.40

Get better results

  • Add doorway openings later subtractively—currently treat wall as uninterrupted sheet area.
  • Check planning portal rules—even small garden buildings may exceed permitted development triggers.
  • Consider damp proof course & sole plate sleeper rot detail—counts don't include fasteners/blocks.
  • Cladding metres² ignore windows—deduct glazing manually if cladding budget tight.
  • Take output to merchants as bill-of-material sanity check, not joinery CNC file.

Reading the numbers

Studs count includes corner doubling assumption from simplified algorithm; sole plates double perimeter per calc function; cladding area is perimeter × wall height including waste—you convert to feather edge packs externally.

Not a substitute for structural sign-off

Toy structural preview—omit wind uplift, diaphragm shear, truss bracing pattern, preservative grading, condensation risk, slab loads. Commission engineer + follow manufacturer details for occupancy or large spans.