Deciding the quota items for pre-laid bond waterproof sheets: taking foundation sheet waterproofing under Beijing DB11/T 2382-2024 as the example, separating the "pre-laying method" items from the "torch-on method" items by construction process, with item work content, consumption and the companion measurement rules

Topic Positioning

This card answers the quota-item selection for underground foundation / roof sheet waterproofing: which process family the pre-laid bond system (polymer self-adhesive pre-laid waterproof sheets) takes, and how "pre-laying" and "torch-on" are told apart from the nature of the process. It lands on foundation sheet waterproofing under Beijing DB11/T 2382-2024 Construction Works Consumption Quota Standard (table A.9.5-1), citing the matching provisions of the underground works waterproofing standard and the bill measurement standard.

Core Conclusions

1. Process-first principle (the master rule)

DB11/T 2382-2024 clause 4.10.8, original: "sheet waterproofing shall be itemised and determined with construction processes distinguished." Different process - different item; items must not be mixed merely for being "sheet waterproofing alike". Pre-laid bond is a cold-applied self-adhesive process, a different process from torch-on (open-flame melting of the heat-fusion coating on the sheet underside); each must map to its own items.

2. The pre-laying items and consumption for pre-laid bond

Beijing DB11/T 2382-2024 Annex A table A.9.5-1 (foundation sheet waterproofing) sets items by process and position; pre-laid bond maps to:

• A-9-243 HDPE self-adhesive film sheet (pre-laying), raft single layer, unit m2. Work content: "cleaning the substrate, applying primer, laying the additional layer and the waterproof sheet, joints, edge termination etc." Consumption: all-in labour Grade II (000105010000) 0.0630 workday; HDPE film waterproof sheet 1.2 mm (133309050100) 1.3760 m2; polyethylene rod d50 (021500000100) 0.0800 kg; other materials (340000110000) 1.5%; other plant (994600040000) 2.0%.
• A-9-244 HDPE self-adhesive film sheet (pre-laying), flat slab single layer, unit m2. Work content as above. Consumption: all-in labour Grade II 0.0600 workday; HDPE film waterproof sheet 1.2 mm 1.2510 m2; polyethylene rod d50 0.0800 kg; other materials 1.5%; other plant 2.0%.

3. The raft / flat slab position split

DB11/T 2382-2024 clause 4.10.17, original: "in foundation sheet waterproofing, where a foundation beam projects downward below the full raft slab, the raft items apply; where it projects upward above the raft slab, the flat slab items apply." Within the pre-laying family, choose A-9-243 (raft) or A-9-244 (flat slab) accordingly.

4. Laps, additional layers and closures are included, not charged extra

DB11/T 2382-2024 clause 4.10.9, original: "the waterproofing construction consumption shall include the work content of lapping, and of additional layers and closures at internal and external corners, post-cast strips, sump pits, lift pits etc." The bill side matches: GB/T 50854-2024 Annex J.6.10, original: "the laps, seam joints, edge turns and step laps of the waterproof and separation layers in this annex, and the additional layer quantities needed to satisfy the construction code, are not computed separately. But additional layers with dimensions marked in the design documents shall have their quantities computed and listed under separate codes with the layer material and detail as item descriptions."

5. The prohibited zone: pre-laid / self-adhesive sheets must not be torched

GB/T 51310-2018 Standard for Construction of Metro Works, clause 16.3.2, original: "the selection of waterproof sheets shall match the structural construction method, and the waterproof material's application process shall match the material's nature." Commentary: "the process must match the material type - cold-applied self-adhesive sheets must not be laid by the torch-on method." Applying the torch-on items to pre-laid bond sheets is therefore a process mis-application.

6. Identification features of the two processes

• Pre-laid bond (pre-laying): the sheet is laid first with the bond face (self-adhesive layer / sand face) up, relying on the later cast structural concrete to bond tightly to it; on floor slabs it is preferably loose-laid or spot-bonded, on vertical faces preferably mechanically fixed (fixings 10-20 mm from the sheet edge at 400-600 mm centres, the fixed spots covered by another sheet); the sheet is laid single layer with no protective or separation layer on its surface; for polymer self-adhesive pre-laid sheets the long edges lap self-adhesively or weld by hot air, the short ends lap with tape or butt (DBJ/T 15-19-2020 clause 6.2.7). Cold applied.
• Torch-on: defined in T/SCIA 001-2021 clause 2.0.5 - "the construction method of heating and melting the heat-fusion coating on the underside of heat-fusion waterproof sheets with dedicated heating equipment, and adhering them thereby." GB/T 51310-2018 clause 16.3.11: heating shall be even, on the broad faces until the surface bitumen melts to a sheen; even roller pressure follows the laying; on walls, laps between upper and lower layers must not form reverse steps; fire precautions on site. Torch-on chiefly suits SBS (elastomeric) modified asphalt waterproof sheets.
• Pre-laid bond versus the conventional plastic waterproof boards of mining works: plastic boards bond to neither the primary nor the secondary lining and need a grout-port system to fill the gap; polymer pre-laid bond sheets adhere tightly to the cast concrete through their self-adhesive layer and carry no grout-port system (companion note to GB/T 51310-2018 clause 16.5.5).

7. Where the sheet type differs from the quota

The process item stands; execute its labour, plant and auxiliary material consumption unchanged and only swap the main material (sheet) price and quantity basis; only where the quota lacks the item and no analogous item exists does the supplementary unit-rate build-up schedule route (compilation and approval) apply.

Applicability Boundaries

• Item codes and consumption come from Beijing DB11/T 2382-2024, Annex A (building and decoration works), table A.9.5-1 foundation sheet waterproofing, and apply only where that standard governs; other provinces apply the corresponding process items of their current consumption quota.
• The process-first principle (itemising by construction process) is a general test portable across regions and quota systems; but the concrete item codes (A-9-243 / A-9-244; Beijing 2021 edition codes 9-243 / 9-244) shift with quota edition and region - check the current item tables before use.
• This card settles "which process item"; it does not settle position measurement and deductions / merges of quantities - those are on the waterproofing measurement-rule cards.
• The pre-laying items presuppose cold-applied self-adhesive sheets (polymer self-adhesive pre-laid waterproof sheets etc.); SBS modified asphalt sheets must not take the pre-laying items - they take torch-on.
• The consumption is the quota's determination and excludes labour, material and plant unit prices and on-costs; prices follow the compiling-period market prices and the companion on-cost quota.

Further Reading

• DB11/T 2382-2024 Construction Works Consumption Quota Standard, chapter 4 building and decoration works, section 4.10 roof and waterproofing works, key clauses: 4.10.8 (itemising by process), 4.10.9 (laps and additional layers included), 4.10.16 (the 300 mm floor-waterproofing upturn split), 4.10.17 (raft / flat slab split), 4.10.19 to 4.10.28 (quantity rules); Annex A table A.9.5-1 foundation sheet waterproofing, items A-9-243 (raft single layer) and A-9-244 (flat slab single layer).
• GB/T 51310-2018 Standard for Construction of Metro Works, clause 16.3.2 (sheet / method matching; self-adhesive sheets must not be torched), 16.3.11 (torch-on laying rules), 16.5.5 (pre-laid bond polymer self-adhesive sheet construction).
• GB/T 50854-2024 quantity take-off standard for building and decoration works, Annex J roof and waterproofing works, J.6.10 (laps and additional layer quantities not computed separately).
• DBJ/T 15-19-2020 Technical Regulation for Building Waterproofing Works, clause 6.2.7 (pre-laid bond process flow, fixing and lap requirements).
• T/SCIA 001-2021 Standard for Construction Quality of Underground Waterproofing Works, clause 2.0.5 (torch-on terminology).