Consultancy
& Design

To comply with the statutory requirements of the Building safety act you must comply with the advice in BS8102

The Stages of Waterproofing Design

Waterproofing design is a vital part of any below-ground construction project.

Getting it right at the earliest stage prevents costly failures and disputes later.

The process begins at the pre-tender stage, where it is essential to allocate a budget for a waterproofing consultant.

This early involvement ensures compliance with British Standards and sets the foundation for a robust design.

RIBA Stages 0-2

Strategic Definition, Preparation and Brief, Concept Design

A waterproofing specialist should be appointed as part of the design team before technical design so that an integrated waterproofing solution is created.

RIBA Stage 3

Spatial Coordination

RIBA Stage 4

Technical Design

Why do I need a waterproofing consultant / specialist ?

British Standard BS8102:2022 requires that a suitably qualified and experienced waterproofing specialist is appointed before the technical design stage.

In practice, this means that before RIBA Stage 3, you should formally engage a waterproofing consultant.

Their role is to provide expert advice before any waterproofing system is specified or designed, ensuring that the chosen approach is practical, compliant, and tailored to the project’s needs.

Waterproofing Specialist Requirements

These are what we think are the minimum requirements for your specialist to meet.

Having PI Specific to waterproofing is essential

They must be CSSW, WDS qualified & be Suitably Experienced

They must be formally appointed

A letter of appointment is required for essential evidence

They must accept design liability.

They must prove suitable on site installation experience at management level

Understanding Basement Grades

So.. what does the specialist do for the project?

As well as dealing with the basement grade as described in the short video above by Ian Maclennan, the consultant / specialist works with your design team to address critical factors.

It is a statutory requirement of the Building safety Act 2022 that the design team ensure the provision of a documented Golden thread of information. The waterproofing specialist must advise on and provide:

1. Risk Assessment

Using site surveys, flood data, and gas risk reports, the specialist produces a formal waterproofing risk assessment. This identifies hazards and recommends controls to reduce risk to acceptable levels.

2. Performance Grade

Together with the client, the specialist determines the required performance grade and provides marked plans showing the grades.

Taking into account:

What finishes will be applied?
What are the consequences of leaks or damp?
What level of risk is acceptable?

Anything less than Grade 3 must come with clear written warnings about potential consequences, which the client must understand and agree to in writing.

3. System Selection

A desktop study of possible waterproofing systems is carried out taking into account the risk, performance grades requirements, construction and requirements for combinations. As well as the necessity for buildability, continuity and repairability and the client guarantee requirements.

4 . Provide accurate Drawings

Carry out 3D detailing: To be used as part of a desktop study as required by BS8102 to consider buildability and detailing.

Provide bespoke CAD drawings of waterproofing detailing

5. With the design team, consider and address..

Buildability: Can the design be installed practically? Only a specialist with installation experience can confirm this.

Continuity: Can the system be installed seamlessly around the structure? This requires expert input on access, sequencing, and safety.

Repairability: BS 8102 is clear: if repairability isn’t addressed, the design must be reconsidered.

Client requirements: Compliance, insurance, training, guarantees, quality control and aftercare requirements must be considered.

6. Specify work required by others regarding..

Preparation
Sequencing
Protection of waterproofing
Related site attendances

7. Advise on basement construction regarding waterproofing

Construction method
Sequencing
De-watering
Service entries
Movement joints

8. Advise on The British Standards regarding..

Testing of systems during and after installation.
Pump installation, commissioning, first service and ongoing servicing requirements.

Finally, it is the responsibility of the Waterproofing Design Specialist to sign off work as compliant with design and advise on guarantees vs retentions, operating manuals and aftercare.

Pre-Tender Design

Why should I pay for pre-tender design?

Pre-tender design is essential because:

It sets up the contract for tender
It ensures compliance with British Standards and insurance requirements
It reduces liability and prevents disputes

Not only that, pre-tender design saves you money and protects you from liability.

At MacLennan, our consultancy fees are very competitive, and our input ensures compliance with British Standards, insurers, and the Building Safety Act.

Unlike manufacturers who offer free design but do not accept liability, we provide continuity from design through installation to aftercare and guaranteed work.

No split responsibility or liability, No grey areas.
Just one accountable partner.

MacLennan take the risk out of waterproofing.

Design input can come from:

Consultants

Typically charge many thousands of pounds per day or a percentage of contract value but will not accept any liability for the final design or detailing. MacLennan provide a full consultancy service and bring real world site installation experience from thousands of projects to the drawing board. You need a site experienced team to consider Buildability, Continuity, Repairability as required by BS8102/22. Design consultancy from Maclennan will cost approximately £1200 per day if put forward as similar or approved with agreed clients' requirements

Manufacturers/Suppliers

Normally charge for design but will not accept any liability,
Might provide free design but it will not be detailed, bespoke or compliant,
Only guarantee materials, Guarantees do not cover design or installation,
Even where they claim it is an overarching guarantee it relies on subcontractors guarantee,
Sub-contractors are often not insured for design.

Specialist Design & Installation Companies

The easiest way to comply with BS8102/22, insurer requirements and The Building Safety Act 2022 is to employ a design and build contractor like MacLennan.
Pre tender design is provided at a cost by the MacLennan design and consultancy team.
Design and installation is taken on by the MacLennan delivery team post tender

Do you need expert advice on Waterproofing?

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The Contractor Design Portion

Contractor design portion?

The most effective procurement method for basement waterproofing is to let it as a contractor design portion, and MacLennan is the ideal delivery partner.

This approach removes the risk of split liability and ensures continuity from design through to installation. We can provide indicative pricing and design proposals early, so you can test the market before committing. Once you’re satisfied, we deliver a full contractor-designed package with complete accountability.

If you choose not to engage MacLennan early, you’ll need strict Employer’s Requirements to protect yourself. But why take that risk when you can work with the UK’s leading waterproofing specialists from day one?

These requirements ensure compliance with BS 8102, building control, insurers, and the Building Safety Act.

Employer’s Requirements Should Include:

The appointment of a waterproofing design specialist such as MacLennan or similar approved, with minimum qualifications of Certified Surveyor in Structural Waterproofing and proven experience on similar projects.
The contractor must take full design liability for basement and deck waterproofing, hold £10 million PI insurance specifically for waterproofing, and remain engaged throughout the design and installation process.
They must maintain a documented quality control system, provide photographic records, offer aftercare services, and deliver 3D detailing of waterproofing.
Guarantees should include a 10-year insurance-backed warranty on workmanship and a 30-year warranty on materials. All work must be carried out by fully employed, qualified staff, no subcontractors.
Additional services such as site meetings, bespoke CAD or 3D drawings can be provided, but charges may apply. Your only commitment when appointing a specialist is to specify “MacLennan or similar approved” in all drawings and tender documents and introduce the specialist to tendering contractors.