Independent validation of a gas membrane installation of permanent ground gas, VOC and waterproof systems is a crucial part of a structure’s construction quality assurance. On many sites, permanent ground gas, VOC and waterproofing protection measures are not inspected and tested or are inspected by non-experts, such as gas membrane manufacturers’ representatives. In many cases, these representatives have little on-site practical experience, and carry no relative insurance in relation to ‘signing off’ an installation.

“The environment agency recommends that conflicts of interest in verification should be avoided. A contractor or gas membrane supplier certifying its own work or product is considered to be a conflict of interest and is not good practice. If verification is carried out by the same company (or related company) that carried out the installation process, the results and report should be audited by an independent consultant”

CIRIA C735 (2014)

GQA Environmental provides site-specific validation plans at the design stage of a project. These include risk assessments in relation to the independent validation required using:

  • Complexity of design
  • Number of plots/buildings
  • Gas regime on site
  • Installation workforce competency

The validation plan sets out the responsibilities of those involved in the full process. The plan also sets out the verification requirements and frequency of any integrity testing and inspection visits. This process should be completed before the installation of the gas protection systems proceeds.

Once work has begun on site, GQA Environmental’s highly experienced inspection engineers manage the validation process. They will highlight through inspection and testing any areas that require remediation by the installation contractor. They will then re-test or inspect these areas before the installation is completed.

A full validation file is produced for submission to the local authority containing:

  • Daily inspection report sheets
  • Integrity testing report sheets
  • Photographic evidence of the installation and remediation on site
  • All other relative documents

This report is covered by relative professional indemnity insurance.



“At Felix O’Hare Ltd we have used GQA Environmental for design advice when working on sites with contamination or waterproofing issues. We have used GQA to provide independent verification of gas and waterproofing protection systems including the integrity testing of them and found them to be easy to work with, technically proficient and highly professional. We look forward to working with them where required in the future”

Mark Campbell – Contracts Director – Felix O’Hare Ltd