Sleeves for rainwater/soil (drainage) pipes through floors: mandatory setting, dimensions and construction, and BOQ measurement (GB 55020-2021 / GB/T 50856-2024)

Topic Positioning

Whether sleeves are mandatory for indoor rain and soil (waste) pipes through floors/walls, how size and construction (height, packing, joint position) are fixed, what additional requirements apply at special positions (waterproofing, fire stopping), and how the BOQ measures them. For water/sewer installation construction, acceptance, and budgeting.

Core Conclusions

1. Mandatory: yes ("shall" in the current mandatory code).

• GB 55020-2021 General Code for Building Water Supply, Drainage and Water Conservation, Clause 8.2.3 (fully mandatory): "Pipes through walls and floors shall be fitted with metal or plastic sleeves. Sleeves in floors: tops 20 mm above the finished floor; in bathrooms and kitchens: 50 mm; bottoms flush with the slab soffit. Sleeves in walls: both ends flush with the finishes. Gaps between floor sleeves and pipes shall be packed with flame-retardant dense material and waterproof ointment, with smooth ends. Wall sleeve gaps should be packed with flame-retardant dense material, ends smooth. Pipe joints shall not be located within sleeves." The clause also requires clean pipes and joints, prevention of debris falling in, temporary sealing of openings at interruption, and notes that a joint inside a sleeve leaks unseen and unmaintainable.
• GB 50242-2002 Clause 3.3.13 worded the same requirements as "should" (20/50 mm heights, packing, joints outside sleeves); GB 55020-2021 upgrades to "shall" — on conflict the fully mandatory code prevails.

2. Size and construction (fallback where unspecified, DB11/T 1832.13-2022 Clause 3.4.4):

• "Sleeve size and length are determined by the structure thickness and the penetrated pipe diameter; the sleeve is preferably two nominal sizes larger" (e.g., DN100 pipe with DN150); insulated pipes' sleeves account for insulation thickness. Sleeve ends perpendicular to the axis, cut clean and burr-free; metal sleeves corrosion-protected inside.
• Selection: basement/underground outer walls -> rigid waterproof sleeves; strict waterproofing -> flexible waterproof sleeves; air-defense walls -> rigid airtight sleeves; plastic risers above ground preferably with protective sleeves.
• Packing: floors/wet positions with flame-retardant (non-combustible) dense material and waterproof ointment, ends smooth; sleeves concentric with pipes and firmly fixed.

3. Special-position additions:

• Waterproof structures: GB 55030-2022 Clause 5.1.10 — "sleeves shall be provided where components penetrate waterproofed structures; the water-stop collar shall be fully welded to the sleeve. After penetration, pack the sleeve-pipe gap dense, and seal the periphery with sealant."
• Plastic drainage risers: GB 50015-2019 Clause 4.4.10 — in high-rises, exposed plastic risers >= dn110 through floors shall have fire-stop devices below the slab (both sides through fire walls; outside shaft walls); GB/T 51188-2016 Clause 10.5.11 — "reliable waterproofing at riser/floor crossings; plastic risers through floors or fire walls shall have fire sleeves and fire-stop collars; through basement walls and roofs, waterproof sleeves or equivalent measures." Collars and sleeves are two items — neither omit nor duplicate.

4. Measurement and listing (GB/T 50856-2024 Appendix N):

• Sleeves are in Appendix N "other and auxiliary works" (031301003), by count per design quantity (one per pipe per penetration); characteristics: name, material, size, packing; work content: fabrication, installation, derusting/painting, packing and sealing, hole blocking.
• Clause N.2.2: "Sleeves apply where required by the design documents and relevant standards; sleeves not so required are included in the work content of the pipe/conduit items of other appendices... different sleeve classes shall be listed separately." Sleeve names mean waterproof (rigid/flexible), general steel, air-defense, and fire sleeves at foundations, walls, beams, floors, structures. Floor penetrations are code-required, hence listed; each class its own item.
• Note: hole reservation (chasing) in new works is in the pipe installation work content, not listed separately; only renovation and changes list under 031301 (see the cross-referenced card).

Applicable Boundaries

• Applies to sleeves of indoor water/sewer (including rain/soil) pipes through floors, walls, waterproof structures, and air-defense walls; municipal buried lines have different calibers — do not mix.
• GB 50242-2002 says "should", GB 55020-2021 "shall" (fully mandatory) — on conflict the mandatory code prevails.
• DB11/T 1832.13-2022 is Beijing local; "two sizes larger" is the fallback when unspecified; other regions check local work rules.
• Same-floor drainage and pre-embedded water-stop sections follow the design; quota application per local installation volumes, sleeve sub-items generally by count tiered by penetrated pipe diameter.

Further Reading

• GB 55020-2021 Clause 8.2.3 (construction and acceptance);
• GB 50242-2002 Clause 3.3.13 and commentary;
• DB11/T 1832.13-2022 Construction Technology Specification for Building Works, Part 13: Water Supply and Drainage, Clause 3.4.4 (with waterproof and airtight sleeve details);
• GB 55030-2022 General Code for Waterproofing of Building and Municipal Works, Clause 5.1.10;
• GB 50015-2019 Clause 4.4.10 and commentary;
• GB/T 51188-2016 Standard for Safety Assessment of Building and Industrial Water Systems, Clause 10.5.11;
• GB/T 50856-2024 Appendix N, Table N.1.1, Clause N.2.2.