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.
There are two possible sources of gas that could be present on a site: they can be natural or they can be a result from its history.
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.
The above gases and vapours all have a variety of properties, such as being asphyxiating, flammable, potentially explosive and others are highly toxic and over several decades of low exposure 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 construction passes independent verification, handover documentation should then be prepared. It should detail any steps required during the construction process to prevent damage as well as for the operation and maintenance of the building.
Specialist advice is highly recommended during the assessment and risk assessment phases of ground gas data. These are the most important documents you need to know and to refer to:
- 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 is 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. As it is becoming increasingly difficult to find suitable sites for development, there has been an increase in the number of brownfield sites. Brownfield sites however can often contain pollutants affecting the ground and 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. The risk nature can impact the duration of monitoring programs.
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.
Ventilation and ground gas membranes are used to mitigate the effects of harmful ground gases. They provide both primary and secondary protection for buildings against the ingress and vapours. 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.
If the gases and vapours pose a danger because of groundwater or soil contamination, remediation can be done to mitigate the situation.
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. This allows them to be light and flexible while still being 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: