Frequently Asked Questions

We have high voltage leak detection equipment that can find damage to the waterproofing element of the roof, therefore testing a dry roof is no problem.

Yes, we have several non-destructive test methods including ELD (Electronic Leak Detection) equipment.

The verification must be undertaken by an independent third party. This should not be the installer or the membrane manufacturer. BS8485:2015+A1:2019 and CIRIA C735 both provide further information on this

We are always keen to be involved as early as possible. This allows us to give input at early stages and potentially avoid changes and amendments later in the design process.

Yes, our design department are very experienced in ground gas design, we often sit on the committees for guidance documents such as CIRIA, BRE and British Standards. We have PI insurance so are happy to provide PI backed designs.

Yes, with our Dec Scanner we are able to provide a full moisture map of your roof, this forms part of our condition report survey.

Yes, using low voltage (wet testing) equipment it is very safe to test a wet roof.

Yes, all sites from CS2 up to CS6 require independent verification, clarity on this can be found in BS8485:2015+A1:2019 and CIRIA C735. It is important to understand that planning consent is dependent on fulfilling the independent verification process, failure to do so could result in planning discharge issues.

Yes, it is arguably more important to get the waterproofing element of blue and green roofs tested as they are then covered by the blue or green element. Discovering a leak after installing and having to remove the sedum or attenuation system is very disruptive and expensive.

LABC Warranty Technical Manual V11 — Section 11.9.3: Blue Roofs

GRO Green Roof Code — Section 3.3.1: Waterproofing Inspection

GRO Green Roof Code — Installation section: Waterproof covering to be tested and approved before works begin

LABC Warranty Technical Manual V11 — Section 11.7.4: Green Roofs

Yes, BR211 was updated in 2023, independent verification of the radon protection system is required –

Under BR211 section 7 Quality of construction and inspection, testing and reporting it states. The inspection, testing and reporting of the installation of the radon ingress protection system is a major factor in the reduction of human error made during construction process and should be carried out by a third-party inspection company independent of the protection system installation contract.

Yes, all our designs are produced with buildability at the forefront of our minds. If a design cannot be installed easily due to obstructions or sequencing, there is a higher risk that the installation will be challenging and not meet the required standard.

The SuDS Manual, (CIRIA C753) the UK’s guidance document for SuDs and Attenuation systems states that third party integrity testing should be undertaken.

Chapter 30 of the SuDS Manual states:

Leakage can occur due to poor field or factory seaming, or damage caused during or after installation. It is important that all joints and seams are visually inspected and tested on site to ensure they meet the required standards.

The Environment Agency recommends that conflicts of interest in verification should be avoided. A contractor or membrane supplier certifying their own work or product is considered to be a conflict of interest and is not good practice.

Independent integrity testing. There is no other way to be certain that your attenuation system is defect free prior to burying.

There is a simple postcode search available at UKradon – UK maps of radon

During new construction the primary protection systems are radon membranes and radon sumps or ventilated voids. BR211 provides guidance on radon protection including photos and illustrations.

Independent inspections provide documented evidence that materials and installation meet specification and manufacturer requirements. This supports warranties, protects the client’s asset, and reduces exposure as the project delivery team if issues arise later.

Always! We consider the site conditions and are guided by the Site Investigation Report, we then produce a fully spec’d design that is suitable for the site and the challenge gases or chemicals.

We would strongly suggest using a specialist membrane installer with experienced and qualified staff. For example, NVQ level 2.

BS8485:2015+A1:2019 would be the top of the hierarchical list of documents. However, NHBC NF94, CIRIA C735, CIRIA C801 and CIRIA C748 all provide excellent information and guidance.

From a management perspective, integrity testing should focus on high-risk details, such as service penetrations. These areas account for the majority of future leak-related defects if not properly assessed.

We consider the guidance in several industry documents, including but not limited to BS8485:2015+A1:2019, BR211, C665, C716, C748, NHBC’s NF94 and the Offsite Alliance Ground Gas Best Practice Guide.

There are several test methods available to our verification engineers when on site. The tests that will be undertaken will be noted in the pre-verification plan and would be site specific. Common tests would be pick and probe – mechanical point testing, air lancing, dielectric testing, inert gas testing and smoke testing.

Basic protection consists of a radon membrane that extends across the footprint of the structure, including bridging any cavities.

Full protection also consist of a membrane as above but also includes ventilation or a radon sump. Further information is available in BR211 from the Building Research Establishment (BRE).

The costs would vary from project to project but would be considerable, below are some examples of what a tank leak on a finished site could cause:

• Digging up roads or car parks
• Closing finished areas
• Claims and programme delays
• Reputational damage

Basic protection consists of a radon membrane that extends across the footprint of the structure, including bridging any cavities.

Full protection also consist of a membrane as above but also includes ventilation or a radon sump. Further information is available in BR211 from the Building Research Establishment (BRE).

Verification visits should be planned at key stages—prior to covering up membranes, after membrane installation. Building this into the programme avoids delays and ensures compliance without impacting critical path activities.

While subcontractor sign-off is important, an independent specialist should be used for waterproofing verification. Third-party verification adds credibility, reassures the client, and gives confidence that risks have been properly managed before sign-off.

To reduce post-handover risk. A waterproofing inspection helps identify concealed defects before finishes are installed or occupancy begins, protecting from costly remedial works, disputes, and warranty claims later.

Water leaking from an attenuation tank could wash away soils and create heave or subsidence. Also, these systems have been designed to reduce the immediate flow of water into the drainage systems, any leakage would prevent the system working optimally.

There are several reasons to test an existing roof. Firstly, a roof that you may intend to completely replace could just need a small amount of repair work, saving money and inconvenience. Secondly, BS6229:2025 stipulates that flat roof should be inspected twice annually, this can often be a clause in a buildings insurance policy.

Most warranties provided require independent integrity testing, and all the major warranty providers make this a requirement.

NHBC Standards Chapter 7.1, Clause 7.1.11

LABC Technical Manual V11, Section 11.6.14 – Flat Roofs: Testing, approved installer and periodic inspection requirements

Premier Guarantee Technical Manual V13, Section 11.6.13 – Flat Roofs: Approved installers and testing requirements

On completion a verification report will be provided, this will contain project details, drawings, and photographic evidence of the installation.