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🔻 The £39,000 Structural Shell – Fully Explained Using Our Standard Design Pack

(View in 3D click here, Foundation • Walls • Warm Roof – all including waste removal)

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🧱 1. Foundations & Reinforced Ground Slab – approx. £14,000

Based on Sheet S101, this system suits 90% of UK residential extensions.

Your drawings show:

• 600mm × 700mm reinforced strip footing with C30 concrete

• 3T12 top & bottom bars + T10 links @ 200mm spacing

• A393 mesh reinforced concrete slab

• Sand blinding, hardcore, full DPM membrane

• Insulation under slab

Included in the £14,000:

• Mini digger + operator

• Excavation of trenches

• Hardcore, sand blinding & compaction

• Steel reinforcement (T12/T10/A393)

• Ready-mix C30 concrete + pump

• DPM + insulation

• Labour crew (1 skilled + 1 helper)

• Rubbish collection & removal

Matches the quantities and day-rates in the 5m × 8m ground slab cost table on S101.

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🏠 2. Exterior Walls & Openings – approx. £14,000

From the wall sections and floor plans on Sheet S102, your wall system includes:

• 100mm dense block inner leaf

• 100mm insulated cavity

• Brick outer leaf

• Wall ties @ 225mm spacing

• DPCs, cavity closers, vertical DPC at junctions

• Lintels for windows + large 6.6m bifold opening (see Lintel Schedule)

Included in the £14,000:

• Dense blocks (7N/mm²)

• Face bricks

• Thermal insulation for cavity

• Sand & cement for internal/external use

• Supply + install of lintels

• Labour for blockwork + brickwork

• Rubbish collection & removal

This matches the 5m × 8m walls cost breakdown shown on S102.

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🪟 3. Warm Flat Roof System – approx. £11,000

Your roof design on Sheet S103 shows a modern, insulated warm roof:

• C24 grade timber joists 50×220 @ 300mm centres for spans up to 6m

• Firring strips to create falls

• External-grade plywood decking

• 150mm rigid warm-roof insulation

• Internal 12.5mm plasterboard

• Flat rooflights

• Waterproofing: Felt or Fibreglass (GRP)

• Fascia, soffits & guttering included

Included in the £11,000:

• All C24 timber

• Firrings, noggins, plywood

• Rigid insulation

• Rooflight trimming

• GRP/Felt waterproofing

• Carpenters + helper

• Rubbish collection & removal

The values align with the Roof Cost Schedule on S103 (≈£330–£390/m²).