CESMM4 – Class G: Concrete Ancillaries

Scope

• Class G covers all ancillary works necessary for in-situ concrete but not part of the concrete volume itself.
• This mainly includes formwork (centering, shuttering, moulds) and other ancillary requirements for casting, shaping, and supporting concrete until it hardens.
• It also includes certain embedded items, finishes, and accessories not included in the main concrete (Class F).

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1. General Principles

• Formwork is measured separately from concrete (Class F) and reinforcement (Class H).
• Measurement is typically in square metres (m²) of surface in contact with concrete.
• Formwork items must be described clearly to indicate:
  • Type of member (slab, beam, wall, column, stair, foundation, etc.).
  • Orientation (horizontal, vertical, inclined).
  • Finish required (ordinary, fair-faced, smooth, textured).
  • Re-use or special forms (curved, complex moulds, architectural).

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2. Sub-classifications under Class G

G1 – Formwork to Foundations and Blinding

• Vertical or horizontal formwork for foundations, bases, and other below-ground works.
• Includes trenches, pad bases, pile caps.

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G2 – Formwork to Walls

• Vertical formwork to concrete walls, retaining walls, basement walls.
• Internal or external faces measured separately if specified.

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G3 – Formwork to Columns and Piers

• Formwork for vertical structural members:
  • Square or rectangular columns.
  • Circular or polygonal columns.
  • Piers and pedestal bases.

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G4 – Formwork to Beams, Lintels, and Girders

• Soffits and sides of beams.
• Includes small structural elements like lintels.
• Complex beam formwork (e.g., curved beams) must be described separately.

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G5 – Formwork to Slabs, Floors, and Roofs

• Horizontal or inclined surfaces:
  • Floor slabs.
  • Roof slabs.
  • Ramps and stair landings.
• Measured by area of soffit.

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G6 – Formwork to Stairs

• Includes risers, treads, landings, soffits, and sides.
• Separate description if the finish is architectural or decorative.

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G7 – Special Formwork

• For curved, ribbed, or decorative concrete surfaces.
• Includes fair-faced formwork or moulds requiring special treatment (plastic, steel, plywood, etc.).

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G8 – Ancillary Concrete Works

• Construction joints (if formed).
• Stop-ends for jointing.
• Chamfers, rebates, drips, grooves, keyways formed by inserts.
• Measured by length (m) or number (no.).

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3. Measurement Rules

• Net surface area in contact with concrete is measured in m².
• Deductions are made for openings >0.5 m² (small holes ignored).
• Separate items for ordinary formwork vs. fair-faced/architectural formwork.
• Formwork to inclined or curved surfaces described separately.
• Temporary supports/scaffolding for formwork are not measured (deemed included in rates).

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4. Information Required in Bill Descriptions

Each formwork item should specify:

• Structural member (beam, slab, wall, etc.).
• Orientation (horizontal, vertical, inclined).
• Finish (smooth, rough, fair-faced, architectural).
• Material type (timber, steel, plywood, plastic moulds if special).
• Shape/complexity (curved, ribbed, waffle, dome, etc.).

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5. Example BOQ Items (Class G)

1. Formwork to vertical sides of strip foundation bases (m²).
2. Formwork to soffit of ground floor slab, horizontal, 200 mm thick (m²).
3. Formwork to sides of beams, 450 mm deep, at first floor level (m²).
4. Formwork to circular columns, 400 mm diameter, up to 4 m high (m²).
5. Formwork to inclined stair soffit and risers (m²).
6. Fair-faced formwork to exposed wall surface, 150 m².
7. Chamfer 25 × 25 mm formed in concrete beams, 100 m length (m).

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✅ Summary

• Class G separates formwork and ancillary works from concrete to ensure transparency.
• Measured in surface area (m²) of contact with concrete, not volume.
• Requires detailed description of type, orientation, finish, and complexity.
• Ensures contractors price correctly for labour, materials, and special finishes in formwork.