China Roofing Codes (GB 50345 and GB 55030)

Roofing in mainland China is governed by national standards with the prefix GB (guobiao, "national standard"). Two are central for roofs.

GB 50345-2012: Technical code for roof engineering

GB 50345-2012, Technical Code for Roof Engineering, was approved on 28 May 2012 and implemented on 1 October 2012. It was issued by the Ministry of Housing and Urban-Rural Development (MOHURD) together with the then General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ). It applies to the design and construction of roof engineering for buildings. Appendices list standards and key performance indexes for waterproofing and thermal insulation materials.

The code covers roof types common in China, including:

• flat (low-slope) roofs with membrane or coating waterproofing, often with protective layers or tiles above
• tiled pitched roofs
• metal panel roofs
• planted (green) roofs

It also addresses thermal insulation layers, drainage, details at parapets and penetrations, and construction quality.

GB 55030-2022: General code for building and municipal waterproofing

GB 55030-2022, General code for waterproofing of building and municipal engineering, was issued on 27 September 2022 by MOHURD and the State Administration for Market Regulation and took effect on 1 April 2023. It is one of China's newer "general codes" (the GB 55xxx series), which contain compulsory provisions: the code states that waterproofing works must comply with it.

For roofs, it sets out:

• a minimum waterproofing design working life of 20 years for roof projects
• three waterproofing grades (I, II and III) based on the type of project and its environment
• a requirement that planted roofs be Grade I, with at least one root-resistant waterproof layer and a protective layer
• minimum thicknesses for single-layer exposed membranes (such as PVC, TPO or EPDM) on metal roof decks of 1.8 mm, 1.5 mm and 1.2 mm (about 0.071, 0.059 and 0.047 in) for Grades I, II and III
• treatment of fully welded sheet metal roofing as a Grade I waterproofing method

Gutters and enclosed balconies must match the waterproofing grade of the main roof.

Effect on the market

GB 55030 raised minimum requirements compared with earlier practice, increasing the number of waterproof layers or their thickness on many projects. Where GB 50345 and GB 55030 differ, the general code's compulsory provisions take precedence, and related technical codes are being revised to align with it.

Other relevant standards

Loads on roofs, including wind and snow, are set by the national load code for building structures. Product standards for membranes, coatings, tiles and metal sheets are issued as GB or GB/T (recommended) standards and as industry standards (JC, JG).