Waterproofing quantity calculation rules: part-by-part measurement and deduction/merge rules for foundation base slabs, floors, walls, and roofs

Topic Positioning

Part-specific rules for waterproofing (membrane/coating/rigid) quantity calculation: the measurement calibers and deduction/merge rules for foundation base slabs, floors, walls, and roofs, plus the measurement of special items such as division joints, pile heads, and anchor heads. Applies to BOQ and consumption calculation in building, municipal, and utility tunnel works.

Core Conclusions

Waterproofing quantities are in principle calculated by area (sqm) per design-drawn dimensions:

1. Foundation base slabs: pile-head areas are not deducted; pile-head wrapping waterproofing is counted by projection extended 300 mm outward; floor trenches are counted into the plane by developed area; foundation side-face and top-surface waterproofing merges into the foundation; retaining walls above the raft are listed as wall waterproofing (GB/T 50854-2024 Appendix J.6.9).
2. Floors/roofs: by net clear area between main walls (floors) or drawn area (roofs), deducting structures and equipment foundations protruding from the floor, not deducting partition walls or columns, pilasters, and holes with individual area <= 0.3 sqm; at plane-vertical transitions, upturns (turn-ups) <= 300 mm merge into the plane by developed area, > 300 mm are listed as wall/vertical waterproofing (GB/T 50854-2024 Appendix J.6.8).
3. Walls: deduct holes > 0.3 sqm; the side faces of attached columns and wall pilasters merge into the wall.
4. Rigid waterproofing/moisture-proof layers: by net clear area between main walls, deducting structures and equipment foundations, not deducting columns, pilasters, and holes <= 0.3 sqm.
5. Special items: division joints by length (m); pile-head waterproofing by piece for pile diameter <= 500 mm, by developed area for > 500 mm; anchor heads by piece; substrate treatment, isolation layers, and underground exterior-wall protection layers by area. Coating waterproofing already includes reinforcement at internal/external corners and pipe openings — not counted separately.

Applicable Boundaries

Based on SJG 111.2-2022 and SJG 181.5-2024 (Shenzhen consumption standards) and GB/T 50854-2024 building and decoration quantity calculation standard; other regional/industry calibers may differ slightly (e.g., the upturn height threshold) — the contract agreement and the applicable standard govern. This card covers measurement rules only; labor adjustment coefficients and material loss for quota pricing require the corresponding quota volume notes.

Further Reading

See SJG 111.2-2022 Volume 2 utility tunnel building and decoration works Clauses 7.2.1-7.2.7 (base slab/floor/wall/rigid waterproofing); SJG 181.5-2024 Volume 5 water treatment works Clause 1.2.4 (including pile heads, anchor heads, division joints, substrate treatment); GB/T 50854-2024 Appendices J.6.8 and J.6.9 (300 mm upturn boundary, foundation side faces merged); SJG 84-2020 municipal maintenance consumption standard Volume 2, corresponding waterproofing clauses.