Deciding the volume attribution of indoor waterproofing (floor / wall sheeting, coatings, waterproof mortars): the waterproof layers themselves take the "roof and waterproofing works" volume, while the decoration floor chapter carries only the dependent build-up - blinding, levelling and protection

Topic Positioning

Deciding which volume of the cost document the waterproofing of wet rooms (bathrooms, kitchens, enclosed balconies) belongs to: the building-works "roof and waterproofing works" volume, or the decoration-works "floors" volume.

Core Conclusions

1. The split stated outright (Shenzhen SJG 77-2020 Standard for Dividing Work Items and Preliminary Items in Building Works Cost Documents)

• Clause 5.6.10 (above ground), original: "above-ground floor decoration works preferably comprise floor blinding, levelling, rebar fabrication and fixing within the build-ups, protection, insulation, thermal isolation, anti-corrosion, paints, tile and other finishes and skirtings, excluding coating and sheet waterproofing. Above-ground coating and sheet waterproofing lists under 5.6.9 above-ground roof and waterproofing works; the interface of above-ground floors with external civil works follows the design documents."
• Clause 5.5.10 (basements), original: "basement floor decoration works preferably comprise ... excluding coating and sheet waterproofing. Basement coating and sheet waterproofing lists under 5.5.9 basement waterproofing works; the interface of basement floors with external civil works follows the design documents."

2. The bill basis agrees (GB/T 50854-2024 quantity take-off standard for building and decoration works)

• Waterproofing sits in Annex J roof and waterproofing works: table J.4.1 "floor (ground) waterproofing and damp-proofing" (code 010904) and table J.3.1 "wall waterproofing and damp-proofing" (code 010903). Floor decoration sits in Annex L, wall and column decoration in Annex M.
• Clause J.6.11 fixes the "split and assign" of build-ups: "wall waterproofing screeds list under the 'vertical mortar screed' items of Annex M; floor and foundation waterproofing screeds under the screed items of Annex L floor decoration; the fine-gravel protection of foundation waterproofing under the 'fine-gravel concrete floor' items of Annex L."

3. The consumption-standard structure confirms (Beijing DB11/T 2382-2024) "Floor (ground) waterproofing and damp-proofing" is compiled into section 4.10 roof and waterproofing works, apart from "floor decoration works". Clause 4.10.11: "valley, eaves gutter, overhanging-eave and canopy waterproofing may follow the roof items; balcony waterproofing may follow the floor waterproofing and damp-proofing items." Clause 4.10.16: "floor waterproofing upturns of 300 mm or less follow the floor waterproofing items; above 300 mm the wall waterproofing items."

4. One indoor waterproofing detail usually spans two volumes Levelling screed (decoration volume, floors / walls) -> waterproof layer proper (waterproofing volume, floor / wall waterproofing) -> protection (decoration volume, floors). That "levelling / protection" sits in the floors volume is no reason to pull the waterproof layer into it too.

5. "Damp-proof course" is not "indoor waterproof layer" - do not mix GB 50037-2013 Code for Design of Building Floors, clause 2.0.6, original: "damp course: the build-up preventing ground moisture from rising through the floor." The damp-course items the decoration floor chapter historically carries (bitumen / bitumen-felt / waterproof-mortar damp courses) block rising ground moisture; what wet rooms (bathrooms, kitchens) receive is a waterproof layer (waterproof defence) - different material systems and governance; one must not substitute the former for the latter in deciding the volume.

Applicability Boundaries

• This decision bounds the attribution of the waterproof layer proper (coatings, sheets); the screeds above and below and the protection still assign to the decoration volume per GB/T 50854-2024 clause J.6.11.
• SJG 77-2020 and DB11/T 2382-2024 are Shenzhen and Beijing local standards; other regions follow their local split standards / quota volume notes; the bill bases of GB/T 50854-2024 Annexes J / L / M apply nationally.
• The interfaces of floors with external civil works, and above ground with below, follow the design documents.
• Upturns 300 mm or less merging into floors, above 300 mm as walls, is a measurement rule and changes no volume attribution.

Further Reading

• Shenzhen SJG 77-2020 Standard for Dividing Work Items and Preliminary Items in Building Works Cost Documents, clauses 5.5.10 (basement floor decoration), 5.6.10 (above-ground floor decoration), 5.5.9 / 5.6.9 (basement waterproofing; above-ground roof and waterproofing).
• GB/T 50854-2024 quantity take-off standard for building and decoration works, Annex J roof and waterproofing works, tables J.3.1 and J.4.1, clause J.6.11; against Annex L floor decoration and Annex M wall and column decoration, partitions and curtain walls.
• Beijing DB11/T 2382-2024 Construction Works Consumption Quota Standard, section 4.10 roof and waterproofing works, notably 4.10.11, 4.10.16, 4.10.20 and 4.10.25.
• GB 50037-2013 Code for Design of Building Floors, clause 2.0.6, damp course terminology.