This quotation sets out the work, the price and what is provisional. Please read the assumptions and exclusions before accepting.

What we will build

• Single-storey extension: 4m × 5m (external), approximately 16.3 m² internal floor area.
• Walls: insulated cavity wall, block inner leaf finished in facing brick.
• Roof: lean-to pitched roof at 22° in concrete interlocking tile.
• Foundations and floor: trench-fill foundations, concrete slab with insulation.
• Windows and doors: 1 × bifold 3×2.1m, 1 × window 1.2×1.2m, 2 × rooflight 0.78×1.18m.
• Completed to: complete finish (standard specification).
• Services: 8 power points, 6 light fittings, radiators from the existing system.

Price breakdown

About the provisional sums

These are estimates for items that cannot be priced firmly yet. They are confirmed with you before that work starts.

• Steel beam and structural design for 1 × 3m opening: A load-bearing opening into the existing house needs a structural engineer's design, a steel beam with padstones and building control sign-off. Allowance covers design and steel supply; the builder's work is priced below.

Assumptions this price relies on

• Foundations: trench fill 600mm wide × 1.0m deep in GEN1 concrete under all new external walls.
• Ground floor: 100mm concrete slab on 150mm compacted hardcore with 100mm PIR insulation.
• Openings over 2.7m wide may need an engineer-specified lintel or steel; a heavy-duty catalogue lintel has been allowed.
• External walls: facing brick outer skin, 100mm full-fill insulated cavity, 100mm block inner skin.
• Lean-to roof at 22° in concrete interlocking tile, cut on site from C24 timber; rafter length 4.3m.
• Drainage: connect rainwater and any foul water to the existing system within 6m, capacity assumed adequate. Building over or near an existing sewer needs the water company's agreement.
• The existing consumer unit has spare capacity for the new circuits; if not, a new unit is extra.
• Heating: 2 radiators added to the existing system; the existing boiler is assumed to have capacity.
• No planning application fee, party wall surveyor or planning drawings are included. Permitted development or existing consent is assumed.
• Work to comply with the building regulations applying in England; design by others where a design is required.

Not included

• Anything not described above.

Programme, validity and payment

• Estimated time on site: about 5 weeks, subject to weather, materials and approvals.
• Payment: Deposit of 10% on acceptance; stage payments at watertight shell, first fix and second fix; balance on completion. Invoices due within 7 days.