Workmen in a basement

What is combination waterproofing?

7 August 2019

At Timberwise we have 50 years of experience in providing interior and external waterproofing solutions throughout the UK. We design and implement waterproofing systems in line with guidelines set out in BS 8102 2009, according to these guidelines Waterproofing Design Specialists should consider using more than one type of waterproofing to provide enhanced protection from water ingress.

Did you know?

Halifax Bank carried out a survey and found Britain has seen a 183% increase in planning applications for basement conversions. Halifax analysed planning data for England, Scotland and Wales over the period January 2012 to December 2016, and found that basements had soared in popularity, especially in London*. 

The types of waterproofing available

Timberwise provides waterproofing products for all three types of waterproofing, defined within BS 8102:2009 as:

Type A: Barrier Protection (External, Sandwiched or Internal)

Type B: Structurally Integral Protection (Usually to the relevant British Standard and of reinforced concrete structure) (BS 8007 and BS 8110)

Type C: Drained Protection (Cavity Drain Membranes and Construction Drained Cavities)

Type C

When is the right time to recommend a combination waterproofing solution?

Waterproofing Design Specialists take into consideration combination waterproofing in particular when:

  • The probability of a leak is very high
  • The consequences of leakage are unacceptable
  • Additional vapour checks are necessary for a system where unacceptable water vapour transmission could otherwise occur
The NHBC imposed in January 2016 in their revised technical manual ‘Chapter 5.4’ that a “dual system” (two waterproofing systems) must be incorporated to structures where a Structural Warranty is provided.

NHBC Technical Manual

What combinations of waterproofing are available?

Type A, B & C        Type A & B               Type A & C          Type B & C

Usually, a combination of 2 forms of waterproofing is adequate when designing a habitable space requiring a completely dry internal environment, defined as ‘Grade 3’ within BS 8102:2009. Whichever combination of waterproofing is chosen to achieve the Grade 3 environment, in most cases the safest combination will include a ‘Type C’ internal cavity drain membrane system as one of the forms of waterproofing. The choice of the other system is largely dictated by the type of structure.

Combination waterproofing design & installation

As recommended by the “BS 8102:2009 – Code of Practice for Protection of Below Ground Structures Against Water From The Ground’ the inclusion of a Waterproofing Design Specialist is essential to design an integrated waterproofing solution.

Timberwise can take full responsibility for the design and liability for the basement waterproofing design in your building project and our systems also meet the guidelines set out by in NHBC chapter 5.4 and Local Authority Building Control (LABC) guidelines.

Combination Waterproofing for a home in South Hams

NB1 Waterproofing Slurry (Type A) & Cavity Drain Membrane (Type C)

In an Area of Outstanding Natural Beauty, this particular detached cottage was constructed with no apparent consideration given to waterproofing the flat roof area or the earth retaining walls.

The owners contacted Timberwise to design and install a waterproofing system. With an office in the local area and 50 years of expertise, the homeowners knew they were in safe hands.

Timberwise’s Waterproofing Design Specialists recommended and installed a liquid/cementitious (Type A) waterproofing system in conjunction with a Type C waterproofing system, this then provides extra protection and continuity of the waterproofing design.

Need Waterproofing Advice? Ask a Timberwise Waterproofing Design Specialist

You can trust Timberwise to provide you with the right waterproofing solution to damp problems in your building. Don’t hesitate to contact Timberwise by calling on 0800 288 8660 or you can request a survey.

A survey through Timberwise will be able to identify the extent of the problem and determine the right waterproofing solution for you and your property.

Originally published 21st October 2018, updated 7th August 2019. 

*Source: https://www.theguardian.com/money/2017/aug/23/underground-basements-halifax-loft-conversions-extend-properties