UK residents are facing increasing problems from dangerous, naturally occurring below-ground gasses and vapours. To protect both the structure and its users, it is crucial that ground gases are identified and managed.
Gases that may be present on a site can be naturally occurring or they may be as a result of its historical use.
Methane, carbon dioxide and nitrogen are all naturally occurring gases. Many of these gases can be found in soil at higher concentrations than normal atmospheric gases.
Sites with a history of heavy industrial use, landfills, or spillage of petrol, oil, or solvents can produce dangerous gases such methane and carbon dioxide.
Each of the gases and vapours mentioned above have different properties. Some are asphyxiating, flammable and potentially explosive. Others can be toxic and, over many decades, can cause cancer. They can also react chemically with concrete and plastic building materials, which could affect the structural integrity of the buildings. They can be found in buildings and other structures above and below ground.
There are many types of gas.
- Radon
- Carbon Dioxide
- Nitrogen
- Methane
- Hydrogen
- Sulphide
- Volatile organic compounds (VOC)
Radon and other gases such as methane (carbon dioxide), methane (carbon dioxide), and VOCs, which are volatile organic compounds such as hydrocarbons, pose a health risk. All new constructions should use appropriate materials to keep these gasses out of their structures.
An independent ‘Gas protector verification plan’ is required in accordance with CIRIA C735. A robust design and construction process should then be followed to install the gas protection measures and the requirements of ‘verification plan’ implemented. After the construction has been verified, it is time to prepare handover documentation. This document should outline any additional measures that may be required, such as those necessary for preventing damage or during operation and maintenance.
Specialist advice is highly recommended during the assessment and risk assessment phases of ground gas data. Here are some key documents that you should be aware of.
- BS 8485:2015+A1:2019 - Codes of practice for the design of protective measures for methane and carbon dioxide ground gases for new buildings.
- CIRIA C748:2014 - Guidance on the use of plastic membranes as VOC vapour barriers
- CIRIA C682:2009 - VOC Handbook
- CIRIA C735:2014 - Good practice on testing and verification of protection systems to buildings from hazardous gases
- BS 8102:2009 - Code of practice for protection of below ground structures against water from the ground
BS8485:2015 + A1 2019 provides recommendations on ground gas site characterisation and the choice of solutions for the design of integral gas protective measures for new buildings to prevent the entry of carbon dioxide and methane and provide a safe internal environment. It can be used as a tool to prove that any potential or actual methane presence has been eliminated.
To ensure the installation of your gas protection systems meets CIRIA 735 & BS8485 please call our Glasgow team
What happens to ground gas?
Why is ground gas becoming a problem?
In the past ground gases where not perceived as a risk to users and the buildings themselves. Due to increasing demand for homes, brownfield sites have seen an increase in development. This is because it is more difficult to find new land to develop. Brownfield sites may contain contaminants that can affect the ground or soil.
Because of increased awareness about the dangers, the Environment Agency has created new legislation that is more strict in dealing with ground gas issues. It has been adopted across the country by local authorities.
Important to remember that ground gas inspections by qualified ground gas surveyors can only determine potential risk factors.
Ground gas risk assessment
First, assess the risk of ground gases and vapours at your desk. Then do a ground investigation or assessment. If ground gases are found to be a concern, then measurements using borehole monitoring wells will be made. You can use static measurement techniques and diffusion tubes in buildings. Monitoring programs can be extended for several days or months, depending on the nature of risk.
Once the investigation has been completed, the analysis and interpretation of measurement data will reveal whether there are ground gases or vapours.
Protection against below-ground gases
Ground gas protection is an extremely specialised operation. GeoShields Ground Gas specialists have the required knowledge, experience and skill levels.
Ground gas protection is often achieved by ventilation and ground membranes in construction. This provides primary and secondary protection against the ingress of gases. If you are already a homeowner living in a property then foundation based ground gas protection will most likely be impractical. Therefore ventilation is the key. You can mix natural ventilation for suspended floors with improved underfloor ventilation or introduce mechanical ventilation systems to control the ground gases and vent them away from your property. In every case, validation of the construction methods and their installation is necessary.
Some cases in which the dangers posed by gases or vapours are due a by-product more severe soil and groundwater contamination can be mitigated through the remediation.
What is the potential impact of not doing anything?
The effect of not reacting to potential ground gas risks depends on which type of ground gas was discovered. Some may affect your health while others can damage the integrity of the building. Radon can cause lung cancer. Carbon Dioxide can cause asphyxiation and can be deadly. Methane, Volatile organic compounds, and Methane can all be explosive/flammable. Low levels of Methane (5%) can make it flammable.
Not only will it have serious consequences for your health, but also the possibility of fire, mortgage lenders may consider the property too dangerous.
What is Ground Gas Membrane exactly?
Due to the hazardous nature of ground gasses, buildings should be protected to ensure safety and integrity. Protection is usually in the for of a ground gas membrane.
Ground gas protection membranes are often made of polymers, but may also contain other materials such as aluminium. They are lightweight, flexible, and easily formable. They can stop gas from getting into buildings and the ground.
To ensure the installation of your gas protection systems meets CIRIA 735 & BS8485 please call our Glasgow team
Other areas near Glasgow we cover include: