BS 8102 Waterproofing Regulations
All of our waterproofing specialists must understand the new revision of BS 8102 and how this may affect their waterproofing design. Although the principles contained within the Code are still sound, after nearly twenty years, BS 8102:1990 Code of Practice for Protection of Structures Against Water from the Ground was overdue for revision.
The Fundamentals of BS 8102:2009
In order for a successful basement waterproofing system to be installed the following must be taken into consideration:
- The use of a specialist designer as part of the team – to check the liability of the system
- The carrying out of risk assessments (sewers, gases, trees)
- Investigation of the water table and surrounding areas
- Accessibility, repairability and servicing of the waterproofing system
The code is not specific about the qualification of the Waterproofing Specialist, which is why the Property Care Association (PCA) has put together a Waterproofing Design Consultant qualification. Design teams will be able to call on these Consultants to assist in the waterproofing element of the design of a property.
Key Legislation / Codes of Practice
- Health & Safety at work act 1974
- The Management of Health & Safety at Work Regulations 1992
- The Environment Protection Act 1990 (EPA)
- BS8102 – Code of practice protection of structures against water from the ground
- Bs8301 – Code of practice for building drainage
- BS8110 – Structured use of concrete. Part 1; code of practice for design and construction
- BS8007 – Code of practice for the design of concrete structures for retaining aqueous liquids
- National House Building Council – NHBC standards volume 1 1991 Chapter 5.3
- Building guarantee technical manual – section 3 & 13 Clause 13.5
BS 8102 – Risk Assessment
A risk assessment should be carried out which considers the long-term water pressures, the effects of surface water infiltration and the use of external drainage and cut-off walls.
When designing a waterproofing system the following MUST be considered:
a) The effects of climate change, burst water mains and sewers, adjacent trees, sulphates, radon, methane and other ground gases and contaminants.
b) Where external drainage is proposed, the effects of drawdown on adjacent structures, the potential silting of drainage and biofouling issues.
Even when the site investigation indicates dry conditions, the risk of some water logging in the future should be assumed.
BS 8102 Fundamental: Waterproofing Designer
A welcome inclusion to the BS 8102 is that it now asks for a waterproofing designer/specialist to be part of the design team at the outset to ensure that an integrated waterproofing solution is realised. The waterproofing specialist must be suitably experienced with efficient qualifications such as being a Certificated Surveyor in Structural Waterproofing (CSSW). Provide the design team with guidance that assists and influences the design, installation and future maintenance of the waterproofed structure.
- Be able to advise and be part of team
- Take on design liability
- Carry our Risk Assessments (sewers, gases, trees)
- Investigate water table and surrounding areas
- Consider accessibility, repairability and servicing
- Design to the required environment grade for Basement uses (Grades 1-3)
- Choose the correct method / Type of Waterproofing System (Type A, B or C)
BS 8102 - Water Pressure
BS 8102 states that regardless of the water table the specialists has to allow for some water pressure to the full height of the basement. The hydrostatic head (from a water table, whether natural or perched) is there for the purpose of the structural engineer, who has to design the structure to resist this water pressure. The code gives more latitude to the engineer to interpret the maximum head he needs to design for, and guidance on these matters.
The code does not specify the source of the water. The most obvious is heavy and persistent rainfall, but it could just as easily be burst water mains, damaged drains or rainwater goods, etc.
BS 8102 - The Defects
Whilst defects owing to poor workmanship can be avoided by proper design, planning and supervision, and the use of skilled workmen, the code now recognises that the defects inherent in the system because of the properties of the materials being used can not necessarily be avoided. Consideration must be given, at the design stage, to the effects of defects, and how they can be overcome should they result in an unacceptable situation.
NHBC (National House Building Council) Chapter 5.4
Owing to increased claims on properties NHBC have developed their own waterproofing guidelines. This affects any new and existing below ground construction which includes: basement, lift pit, cellar split level. NHBC has also set minimum requirements and standards for their own individual property warranties.
Owing to increased claims on properties Premier Guarantee and Local Authority Building Control (LABC) have also developed their own waterproofing guidelines.
The Premier Guarantee and LABC guidelines re-enforce waterproofing guidelines set out in BS 8102.
For More Information
If you would like any more information on the waterproofing regulations or if you have any waterproofing problems then don’t hesitate to get in touch with our team of waterproofing specialists at Timberwise. You can do this by calling on 0800 288 8660 or you can request a survey online. A survey through Timberwise is the starting point to designing a successful waterproofing system for your property.