Ground Gas Assessment & Monitoring
Does the building need protection, and to what standard?
Ground gas and vapour risk depends on the source, the gas regime and the building proposed. We establish what the monitoring evidence actually shows, and specify protection that matches it rather than the worst case imaginable.
For desk-based assessment of existing data. Monitoring programmes to suit the risk.
Does the building need protection?
Whether gas and vapour protection is needed, and to what standard.
No protection, targeted protection, or further monitoring
Based on what the monitoring evidence shows for the proposed building.
Ground gas risk assessment and protection strategy
Suitable for the LPA, for developers, architects, basement designers and building control.
The protection should match the gas regime, not the worst case imaginable.
Measuring gases in the ground, such as methane and carbon dioxide, to decide whether buildings need protection.
Typical triggers include sites on or near made ground, landfill, alluvium or infilled land, basements in boroughs with specific gas guidance, former fuel stations, radon-affected areas and planning conditions requiring gas protection design.
From brief to answer.
Establish whether gas and vapour protection is needed, and to what standard.
Review
Existing ground investigation data, geology, historic land use and local authority requirements.
Monitor
Where needed, gas and vapour monitoring from installed wells over a representative period.
Assess
Source-pathway-receptor assessment and characteristic gas situation for the proposed building.
Specify
Proportionate protection measures and the verification needed to prove they were installed.
Three honest outcomes.
We report what the evidence supports. Each outcome is a legitimate answer, and the first is often the most valuable.
No protection needed
The gas regime presents no material risk to the building.
Targeted protection
Membranes, venting or radon measures specified to the right standard.
Further monitoring
Only where the existing data cannot support a defensible conclusion.
Protection matched to the evidence.
Plain-English conclusions up front, with the technical detail regulators and engineers need behind them.
Guidance we work to: BS 8485, BS 8576 and CIRIA C665.
A recent project.
What this looked like on a real site, and what the client could do as a result.
Gas, vapour and radon protection aligned to borough requirements.
For a residential development in RBKC, Clear assessed ground gas, vapour and radon risk and prepared a remediation strategy recommending proportionate mitigation measures. Delivered within 10 working days, the report aligned with RBKC planning requirements so conditions could be discharged without delay.
Read the case study →Read more on this.
Plain-English guides from our insights, written for developers, buyers and their advisers.
Ground Gas Risk in Kensington & Chelsea: What Developers Need to Know
Ground gas risk guidance for Kensington & Chelsea developments, including when assessment is needed and how monitoring and mitigation are approached.
Discharging Contaminated Land Planning Conditions in the UK
Step-by-step guide to discharging contaminated land planning conditions in the UK. Learn about Phases 1–4, compliance, and commercial benefits.
Do I Need a Phase 3 Remediation Strategy? (And What Is It?)
When a Phase 3 Remediation Strategy is required, what it contains and how practical remediation supports planning and contaminated land management.
Common questions.
Which gases do you assess?
Principally methane and carbon dioxide from made ground and organic deposits, hydrocarbon and solvent vapours from contaminated soils and groundwater, and radon from underlying geology.
Do you work to borough-specific guidance?
Yes. Several London boroughs set out their own expectations. Our RBKC assessment, for example, was aligned to the Royal Borough’s planning requirements so conditions could be discharged without delay.
Get a quote for your site.
Send us the address and what you’re planning. A senior consultant will reply with a quote and the right first step, usually within one working day.