Setting and measuring the height of waterproof upturns (turned-up edges): design first, codes as the floor (GB 55030-2022 and GB 55038-2025 mandatory positions and conflicts with local standards), the datum of the finished floor level, and the 300 mm split between floor and wall waterproofing items

Topic Positioning

Setting and measuring the height of waterproof-layer upturns (turned-up edges), answered on two levels: (1) what height - design first with codes as the floor, the fully mandatory national engineering codes prevailing in conflict, measured from the finished floor level (finish face); (2) how to measure and list - upturns within 300 mm merge into floor waterproofing, those above 300 mm list as wall waterproofing. For design values, quantity take-off and pricing of floor and wall waterproofing in wet rooms such as bathrooms and kitchens.

Core Conclusions

1. Order of setting: (1) the drawings state the waterproof detail and upturn height (prevailing, and never below the code minimum) - (2) where unstated, take the code minimum - (3) where the design conflicts with a fully mandatory national engineering code, the mandatory code prevails.

2. Datum: the finished floor level (finish face), not the structural face. Comparable wording: DB11/T 1811-2020 clause 5.3.1 "the waterproof layer of bathrooms shall turn up the wall to a height of not less than 1800 mm above the finished floor level"; DB33/T 1147-2018 clause 5.5.3 "the floor waterproof layer shall turn up the wall to not less than 250 mm above the floor finish"; JGJ 298-2013 clause 5.4.6 "the floor waterproof layer shall turn up the walls and rise at least 200 mm above the finish".

3. Mandatory national minimum heights (by zone) GB 55030-2022 General Code for Waterproofing of Buildings and Municipal Works, clause 4.6.4 (original): "at the junction of wet and non-wet room floors there shall be measures preventing water from entering the non-wet rooms. The turned-up height of the waterproof layer on shower-zone walls shall be not less than 2000 mm and not lower than the shower head. The turned-up height on walls at wash-basins and other water points shall be not less than 1200 mm. The flashing turned-up height at other wall parts shall be not less than 250 mm." GB 55038-2025 Code for Residential Projects, clause 4.1.9 (original): "bathroom waterproofing and damp-proofing shall comply: 1 bathroom floors shall have a waterproof layer and a floor drain with a drainage slope to the drain of not less than 1%; 2 the wall waterproof layer in bathroom shower zones shall be not less than 2.00 m high and not lower than the shower head, and the remaining walls and the ceiling shall have a damp-proof layer or damp-proofing measures; 3 the wall waterproof layer at wash-basins shall be not less than 1.20 m high; 4 at other bathroom wall parts outside items 2 and 3, the flashing turned-up height of floor waterproofing shall be not less than 0.25 m."

4. Conflicts between local standards and the mandatory national code: where the local standard is lower, set per the national code - 2000/1200/250 mm are floors, not options "slightly above the local standard"; stricter parts of the local standard may be retained. Example: DB/T 29-35-2017 Technical Standard for Residential Decoration in Tianjin, clause 10.3.5, reads "the floor waterproof layer shall extend from the floor onto the walls, 150 mm above the floor. Bathroom wall waterproof heights: not less than 1800 mm in shower zones, not less than 1100 mm at wash-basin zones, not less than 300 mm elsewhere" - the first two are below GB 55030-2022, so set 2000 mm and 1200 mm; the "300 mm elsewhere" is stricter than the national 250 mm and may be retained.

5. Companion details to settle together

• JGJ 367-2015 clause 4.7.14: the floor waterproof layer shall turn up 300 mm at the wall base; wall waterproof height not less than 1.80 m in shower zones and not less than 1.20 m at water points elsewhere; with lightweight walls the wall takes a full-height waterproof layer; pipe penetrations of slabs, floor-wall junctions and floor-drain perimeters and other leak-prone parts take reinforced waterproofing; bathroom floors preferably 5 mm to 15 mm below adjacent rooms.
• JGJ 298-2013 clause 5.4.6: where the wall has a damp-proof layer, the floor waterproof layer shall turn up the walls at least 200 mm above the finish; where bathrooms and kitchens use lightweight partitions, full waterproof walls are required, with a C20 pea-gravel concrete kerb around the base except door openings, at least 200 mm above the adjoining rooms' floor finish.
• DB33/T 1147-2018 clause 5.5.3: bathroom and kitchen floor levels preferably 15 mm to 20 mm below the indoor level; a reinforced concrete upstand kerb as wide as the wall shall be cast at masonry wall bases, not less than 200 mm above the floor, preferably cast together with the slab; the floor waterproof layer shall turn up onto the walls not less than 250 mm above the floor finish, lapping not less than 100 mm onto different wall waterproof materials.
• Horizontal spread at doorways (a parallel check to upturn height): JGJ 298-2013 clause 5.4.1 - "the floor waterproof layer shall spread horizontally at doorways, outwards not less than 500 mm and sideways not less than 200 mm"; DB11/T 1811-2020 clause 5.7.2 same, adding "and turn up the walls to not less than 300 mm above the indoor finished level".

6. Quantity split and listing (GB/T 50854-2024 Annex J)

• Clause J.6.8 (original): "where the floor waterproof upturn height exceeds 300 mm, list under the corresponding wall waterproofing item code."
• Item codes: table J.4.1 floor waterproofing and damp-proofing (code 010904); table J.3.1 wall waterproofing and damp-proofing (code 010903). That is, turned-up parts within 300 mm merge into the floor waterproofing (010904) quantities without separate listing; parts above 300 mm list as wall waterproofing (010903); both computed by area at design-shown dimensions.
• Formula: upturn quantity = developed upturn length (perimeter at the wall junction) x upturn height.

7. Beijing consumption position (DB11/T 2382-2024)

• Clause 4.10.25: turned-up parts of floor waterproofing with upturn height 300 mm or less merge into the floor quantities; clause 4.10.16: upturn 300 mm or less follows the floor waterproofing items, above 300 mm the wall waterproofing items.
• Clause 4.10.9: laps, additional layers and closure at internal and external corners, post-cast strips, sump pits, lift pits etc. are included in the construction consumption and take no separate bill item or quota item.
• Clause 4.10.20: turned-up parts at parapets, expansion joints and roof lights merge into the roof quantities; valleys, eaves gutters, overhanging eaves and canopies merge into the roof quantities on the design-shown developed area; flat roofs by horizontal projection, sloped roofs by slope area.

Applicability Boundaries

• Height values follow the design documents; code minimums apply only where the design is unstated or unclear. The datum is the finished floor level (finish face); measuring from the structural face systematically understates the upturn - keep one datum across design and code.
• GB 55030-2022 is a fully mandatory code and outranks local standards; stricter local parts may be executed, but "local practice" cannot undercut the mandatory floors.
• The "within 300 mm into the plane, above 300 mm as wall items" split is the Beijing building position (DB11/T 2382-2024) and the national position (GB/T 50854-2024 Annex J clause J.6.8); other sector or local systems may use a different split value - do not apply across systems.
• Additional layers and closures are comprehended in the consumption and not charged as incurred; when a within-300 mm upturn merges into the plane item, state the upturn height in the item description per the code.
• This card covers upturn height setting and measurement only - not foundation-mat waterproofing or pile-head waterproofing (non-upturn cases), nor waterproof ponding / spray tests (separate card). Local standards apply by administrative region.

Further Reading

• GB 55030-2022 General Code for Waterproofing of Buildings and Municipal Works, clause 4.6.4 and commentary (fully mandatory)
• GB 55038-2025 Code for Residential Projects, clause 4.1.9 (bathroom waterproofing and damp-proofing)
• GB/T 50854-2024 quantity take-off standard for building and decoration works, Annex J: clause J.6.8, table J.3.1 (010903 wall waterproofing and damp-proofing), table J.4.1 (010904 floor waterproofing and damp-proofing)
• JGJ 298-2013 Technical Code for Interior Waterproofing of Housing, clauses 5.4.1 and 5.4.6
• JGJ 367-2015 Code for Design of Interior Decoration of Housing, clause 4.7.14
• DB11/T 1811-2020 Technical Regulation for Waterproofing of Kitchens and Bathrooms, clauses 5.3.1 and 5.7.2
• DB33/T 1147-2018 Technical Regulation for Building Waterproofing, clause 5.5.3
• DB/T 29-35-2017 Technical Standard for Residential Decoration in Tianjin, clause 10.3.5
• DB11/T 2382-2024 Construction Works Consumption Quota Standard, section 4.10 "roof and waterproofing works", clauses 4.10.9, 4.10.16, 4.10.20, 4.10.25