Scaffolding calculation for water tanks (structures): measurement bases for the inner face of tank walls, the tank floor and birdcage (full-area) scaffolding for the roof slab, and the fee-route determination

Topic Positioning

Scaffolding quantity calculation and charging for water tanks (underground concrete tanks, storage reservoirs and similar structures): first clarify "whether to charge, and along which route", then give the measurement bases for the three parts - the inner face of tank walls, the tank floor, and the roof slab (birdcage scaffolding); and distinguish, for the roof slab, the two categories of "working-type birdcage scaffolding" and "load-bearing formwork support", to prevent mis-measurement and duplicate itemizing.

Core Conclusions

1. Route determination (Beijing official Q&A, deciding "whether to charge separately"): "Where an underground concrete water tank project is located inside a building, per the relevant provisions of the chapter notes to Chapter 17 Scaffolding Works of the 2012 'Beijing Construction Project Pricing Basis - Budget Quota, Building and Decoration Works', its scaffolding cost shall be calculated as comprehensive scaffolding by gross floor area and shall not be charged separately. Where the underground concrete water tank project is outside the building and constitutes an independent work, its scaffolding shall be executed with the corresponding quota sub-items according to the scaffolding construction scheme of the specific project." -> When the tank is inside a building, the inner face of the walls, the tank floor and the roof-slab birdcage scaffolding must not be itemized separately (a high-frequency double-charging point); only when it is confirmed as an independent work are the corresponding quota sub-items applied part by part per the approved construction scheme. 2. Inner face of tank walls: measured by the vertical projected area of the working face. The volume notes of the railway TB/T 10832-2024 "Railway Engineering Budget Quota, Volume 11 Water Supply and Drainage Works" provide that "the quantity of water-tank scaffolding is calculated by the tank-wall area", corresponding to sub-item PY-483 "erection and dismantling of water-tank scaffolding, steel-pipe type" (unit 100 m2, base price RMB 845.15). Jiangsu 2026 consumption standard: for water (oil) tanks over 3.60 m in height, the concrete-pouring scaffolding is calculated in square metres as the outer-wall perimeter multiplied by the wall height, applying the tank-wall concrete-pouring scaffolding sub-item; where plastering is executed, plastering scaffolding is charged separately. Where access scaffolding is actually erected on both the inner and outer sides, both shall be calculated. 3. Tank floor: generally no separate "tank-floor scaffolding" item. The notes to Appendix C of GB/T 50860-2024 "Standard for Calculation of Quantities of Structures Works": "The measures items of Appendix C of this standard do not include scaffolding with an erection height within 3.6 m. The cost of scaffolding with an erection height within 3.6 m shall be considered in the all-in unit rates of the corresponding divisional work quantity lists." The tank floor is merely the erection base surface for the interior birdcage scaffolding / inside scaffolds. 4. Working-type birdcage scaffolding for the roof slab: per the Hunan 2025 consumption standard - birdcage scaffolding is calculated by the actually erected horizontal projected area, without deducting the areas occupied by attached columns and columns; the basic lift applies to heights above 3.6 m up to 5.2 m; above 5.2 m, one additional lift is counted per 1.2 m, the number of additional lifts = (height - 5.2 m)/1.2 m, rounded to the nearest integer. Corresponding railway sub-items: FY-440 "birdcage scaffolding, basic lift, indoor clear height 3.6 m < H <= 5.2 m" (100 m2, base price RMB 1,101.25), FY-441 "birdcage scaffolding, additional lift, each +1.2 m" (100 m2, base price RMB 199.12). Shenzhen SJG 181.2-2024 "Municipal Engineering Consumption Standard, Volume 2 Bridge and Culvert Works" Clause 8.2.4: full-scaffolding quantities are calculated in cubic metres by the spatial volume actually erected and dismantled - the dimension differs from the area basis; note the conversion difference when using it across regions. 5. Load-bearing formwork support for the roof slab (parallel to the access scaffold, different basis): measured by the contact area between the formwork and the cast-in-place concrete member; Beijing DB11/T 2382-2024 Clause 4.17.1(4): columns, beams, walls and slabs shall be determined separately by formwork height (the height from the outdoor design ground or the slab surface to the slab soffit); the part within 3.60 m is determined comprehensively regardless of height; the part exceeding 3.60 m is determined comprehensively as "each additional 1 m of formwork support height above 3.60 m", its quantity being the whole area of the exceeding part; where the exceeding part is less than 1 m, the "each additional 1 m" item applies. Corresponding Beijing municipal quota sub-item D5-3-14 "formwork, tank-cover formwork height exceeding 3.6 m, each additional 1 m" (unit m2). 6. Wall-floor division line (Beijing DB11/T 2382-2024 Clause 9.2.2): where a wall-base beam exists, the boundary is the underside of the wall-base beam - above it the tank wall, below it the floor slab; without a wall-base beam, the conical bottom is measured to the upper surface of the slope and the enlarged lower part of the wall is counted into the floor-slab volume. Railway basis: the floor volume includes the enlarged lower part of the wall; the conical bottom is measured to the underside of the wall-base beam, or to the upper edge of the conical slope where no wall-base beam exists; the wall height is measured from the top surface of the floor slab to the underside of the tank cover, by actual volume. Columns and partition walls inside the tank follow the corresponding items of other structures (Beijing Clause 9.2.3). 7. BOQ basis: Appendix C of GB/T 50860-2024 "scaffolding" covers all scaffolding erected during the construction of the works as required by the relevant codes.

Applicable Boundaries

• The route determination "inside a building -> comprehensive scaffolding, no separate charge; independent work -> sub-items per the construction scheme" comes from the official Q&A of the Beijing Municipal Commission of Housing and Urban-Rural Development; other regions are governed by their local pricing bases and official interpretations.
• Regional/industry measurement bases differ: by tank-wall area (railway), by outer-wall perimeter x wall height (Jiangsu), by horizontal projected area + additional lifts (Hunan), by spatial volume (Shenzhen) - cross-region use must be adjusted to the local current consumption standard/quota; sub-item numbers (PY, FY, D5-3-14 etc.) are specific to their own quotas and must not be transferred across standards.
• The basic-lift/additional-lift parameters (3.6 m/5.2 m/1.2 m) are common bases; the specific steps are subject to the quota of the region concerned.
• The conclusion "scaffolding within 3.6 m is not itemized separately" applies to the measures-items basis of the BOQ standard (GB/T 50860-2024 Appendix C).
• Where the roof slab involves both a working birdcage scaffold and a load-bearing formwork support, their work content and measurement bases differ; itemizing must avoid double charging.
• This card sorts out measurement bases; the scaffold configuration and quantities of an independent work are governed by the approved construction scheme and the local pricing basis.

Further Reading

• Beijing: DB11/T 2382-2024 "Construction Consumption Standard" Sections 9.2 (concrete structures), 9.5 (measures items), 4.17 (measures items); the original Beijing MHCURD official Q&A on scaffolding for underground concrete water tanks: https://zjw.beijing.gov.cn/bjjs/gczj14/xhlbz/ys20/cjwd33/743942038/index.shtml
• Railway: TB/T 10832-2024 "Railway Engineering Budget Quota, Volume 11 Water Supply and Drainage Works", volume notes "IV. Quantity calculation rules (1) reinforced concrete water tanks" and Chapter 4 Section 3 PY-483; TB/T 10831-2024 "Railway Engineering Budget Quota, Volume 10 Building Works" FY-440/441/442.
• National standard: GB/T 50860-2024 "Standard for Calculation of Quantities of Structures Works" Appendix C and its provisions (scaffolding within 3.6 m included in all-in unit rates).
• Shenzhen: SJG 181.2-2024 "Municipal Engineering Consumption Standard, Volume 2 Bridge and Culvert Works" Clause 8.2.4; Jiangsu: 2026 edition Jiangsu Province building and decoration consumption standard (scaffolding works); Hunan: 2025 edition Hunan Province building and decoration consumption standard (full-scaffolding calculation rules).