The mandatory engineering construction standard "General Code for Waterproofing of Building and Municipal Engineering" GB 55030-2022, which will be implemented on April 1st, stipulates that the design service life of indoor waterproofing in buildings should not be less than 25 years, and the waterproofing grade should be determined based on the type of indoor waterproofing in buildings and the waterproof usage environment. Starting from the functional requirements of waterproofing in building interior engineering, how to determine the standards and levels of waterproofing in building interiors?

1. Scope of waterproofing protection for indoor construction projects

Indoor waterproofing in buildings generally includes kitchens and bathrooms in residential buildings, kitchens in public buildings (including kitchens in the catering industry and internal canteens), public toilets, public bathrooms, boiling water rooms, and other rooms with independent water containers (such as cleaning rooms with sewage tanks), as well as enclosed balconies with water distribution points.

2. Waterproof grade of indoor engineering in buildings

The general specification stipulates that the working life of waterproofing design for indoor building engineering should not be less than 25 years, and the waterproofing grade should be determined based on the type of waterproofing for indoor building engineering and the waterproof usage environment. Article 2.0.3 of the General Specification stipulates that the waterproofing category for indoor construction projects in buildings is Class A. Article 2.0.4 classifies the usage environment, with Class I for frequent water exposure or long-term relative humidity RH ≥ 90%, Class II for intermittent water exposure, and Class III for occasional water leakage that may cause significant losses. According to the provisions of Article 2.0.6 on waterproofing grade, the indoor waterproofing grade of buildings should be selected according to the following table:

Because the waterproofing category of the project is Class A, according to Article 2.0.6 of GB 55030-2022, except for Class III usage environment which is classified as Grade II waterproofing level, all others are classified as Grade I waterproofing protection level. However, Class III usage environments are relatively rare in construction projects, so the waterproofing design of indoor building waterproofing projects is mainly based on Level 1.

For the environment of engineering waterproofing, further clarification has been made in the provisions of the general specifications. Class I includes rooms that require frequent water use, such as bathrooms, kitchens, laundry rooms, shower rooms, floors that are frequently cleaned with water, processing sites that require a large amount of water, and rooms with long-term high humidity, such as wet sauna rooms and steam curing rooms; Class II refers to floors that require water cleaning, etc; Class III refers to situations where there may be equipment pipeline leakage.

In actual use, although household kitchens and laundry rooms consume a large amount of water, there is very little water overflowing from the sink and washing machine. Generally, wet cloths or mops are used for floor cleaning, and water flushing is not necessary. Therefore, the waterproof environment of household kitchens and laundry rooms is quite different from that of catering kitchens. Therefore, according to the actual situation of the project, the indoor waterproof environment category of the building should be clarified. For example, the waterproof environment category of catering kitchens can be Class I, while that of household kitchens can be Class II or even Class III, in order to determine the waterproof function requirements, standards, and waterproof level of the project.

3. Other standards related to waterproofing requirements for building interior engineering

(1) General Code for Civil Buildings GB 55031-2022

Civil buildings refer to buildings used for people's residence, living, and social activities, which can be divided into two categories: one is residential buildings, such as dormitories, residences, apartments, and villas; Another type is public buildings, such as office buildings, schools, libraries, hospitals, sports centers, exhibition halls, cinemas, hotels, shopping malls, stations, docks, airports, etc. The General Code for Civil Buildings specifies the basic dimensions, technical requirements, and general technical measures for building spaces and parts. Articles 6.2.3, 6.3.2, 6.3.3, and 6.4.10 respectively specify the waterproof and moisture-proof requirements for the walls, floors, ceilings, and ceilings of civil buildings

(2) Code for Construction Projects of Dormitories and Hotels GB 55025-2022

Dormitory and hotel buildings belong to non residential residential buildings. The "Dormitory and Hotel Building Project Specification" mainly includes five elements: project scale, layout, function, performance, and key technical measures. It proposes to ensure and maintain the safety of people's lives and property, personal health, engineering safety, ecological environment safety, public rights and interests, promote energy and resource conservation and utilization, and meet the control bottom line requirements of social and economic management. Articles 2.0.7 and 3.2.4 specify the waterproof and moisture-proof requirements for the floors and walls of daily water rooms in dormitories and hotels

(3) Residential Project Specification

A residence refers to a house that provides daily living for a family and is not open to outsiders. The "Residential Project Specification" puts forward relevant requirements from the aspects of living environment, building space, structural safety, indoor environment, and building equipment. Article 4.1.9 of the draft for soliciting opinions stipulates the waterproofing of residential toilets:

Author Zhang Wenhua

Professor, School of civil engineering, Zhejiang University of Technology