Envelope and protection · Sealants & Membranes
Radon and Ground Gas Barrier Membrane
Explains what a gas resistant membrane is, how it differs from a damp-proof membrane, and why ground gas protection is a site-specific matter settled by a qualified specialist rather than by choosing a product.
Educational reference entry. Suitability depends on the complete assembly, substrate, exposure, installation method, manufacturer documentation, local requirements and qualified professional review.
Overview
What radon barrier is
A radon and ground gas barrier is a factory-made sheet, usually polyethylene based and sometimes carrying an aluminium or other low permeability core, produced specifically for resistance to the passage of soil gases. It is supplied with a matched family of jointing tapes, corner units, top hats and pipe collars that are intended to be used together as one product family rather than mixed with general site materials.
The distinction from a damp-proof membrane matters, because the two can look almost identical on a roll. A damp-proof membrane is chosen for liquid water and moisture from the ground; a gas barrier is assessed for gas permeability and is only meaningful as a continuous, sealed installation. Laps, service penetrations, junctions and terminations carry the outcome, so one product cannot simply be swapped for the other.
Nothing about ground gas protection can be settled from a reference page. The measures required for any site follow a site-specific ground gas assessment and the requirements of the relevant authority, a barrier is normally only one part of a wider strategy, and both the design and the verification of the installed work belong to a qualified specialist.
Terminology
Common names and aliases
These names describe the same thing. The library keeps one entry per material so that an acronym, a trade name or a regional spelling never becomes a second, thinner page.
- radon membrane
- ground gas barrier
- gas resistant membrane
Applications
Common applications
Where this material is typically encountered. A typical application is not a statement that it suits your project.
- Substructure work on sites where a ground gas assessment has identified radon or another soil gas as a matter to be addressed.
- New ground floor construction where a designer has called for a gas resistant layer within a wider protection strategy.
- Extension and conversion projects in areas identified as affected, where the approach is set by a specialist for that site.
- Works where the designer wants the gas barrier and the ground damp-proofing considered together rather than as one product doing both jobs.
- Refurbishment schemes where existing substructure protection is being reviewed by a qualified specialist before work is planned.
Consideration
Where it is commonly considered
- Where a site-specific ground gas assessment exists and a qualified specialist has set out what protection the project requires.
- Where the designer wants a documented product family, with matched tapes and collars, rather than an assortment of unrelated components.
- Where the sequence of work allows every lap, penetration and junction to be formed and inspected before it is covered.
- Where the client accepts that verification of the installed work, not the product name, is what any protection rests on.
Professional review
Where additional professional review is especially important
These are the situations where the answer depends on the specific building, and where a qualified professional should be involved before anything is decided.
- Where no ground gas assessment has been carried out, since what is required cannot be known from the material alone.
- Where the construction contains many service penetrations that cannot be detailed with the manufacturer's own components.
- Where a damp-proof membrane is already present and is assumed to do the same job, which only the designer can confirm.
- Where the programme leaves no opportunity to inspect the completed installation before following trades cover it.
- Where the building will later be altered or drilled into by others with no record of what protection exists.
Properties
Key properties to discuss
Qualitative topics worth raising. Measured values, classes and grades come from the manufacturer's technical documentation for the specific product, not from a reference page.
- Moisture behaviour
- Resistance to ground moisture and resistance to soil gas are separate questions. A product may be described for one, the other or both, and only the manufacturer's documentation for the specific sheet indicates which applies.
- Installation dependency
- The outcome is carried by the jointing rather than the sheet. Laps, corners, penetrations and terminations determine whether the installation is continuous, and these are the parts most often compromised on site.
- Documentation
- Ask for the manufacturer's test data, the full component list for the product family and the installation instructions, and expect the specialist to record photographic evidence of the completed detailing.
- Substrate dependency
- The surface the membrane is laid on affects whether it survives the following work. Sharp material, protruding fixings and site traffic all put a thin sheet at risk long before anything covers it.
- Repairability
- Damage found before covering can usually be made good with the manufacturer's own tape. Once the installation is buried, repair becomes disruptive and may not be possible without opening up construction.
- Maintenance
- There is nothing to maintain in the usual sense, but later works that puncture the barrier, such as drilling, service alterations and floor openings, can undo it, which makes a lasting record valuable.
- Appearance
- The barrier is not a visible finish and gives no clue to its condition once covered, so any judgement about it has to come from records made at the time rather than from looking at the building later.
Exposure
Exposure and environmental conditions
- What does the site-specific ground gas assessment say, and who is responsible for turning it into a design?
- Is the groundwater and drainage situation at the site understood, since water movement and gas movement are related questions?
- Will the finished building be sealed and ventilated in the way the protection strategy assumes it will be?
- Are neighbouring or previous land uses relevant to what may be present in the ground here?
- Does the design allow for seasonal and longer term variation in ground conditions rather than a single set of readings?
Assembly
Substrate and system dependencies
What this material sits on, is fixed to or depends on. This is usually where performance is won or lost.
- The strategy as a whole, not the sheet, determines what is achieved, and that strategy is set by a qualified specialist for the particular site.
- Junctions with wall damp-proofing and with any other membrane have to be designed as deliberate details rather than improvised on site.
- Every service entry through the construction becomes a detail the design has to resolve using components made for the purpose.
- The order in which trades work decides whether the installation can be completed and checked without being disturbed.
- Protection from following work has to be planned, because a thin sheet does not survive unprotected site traffic.
Appearance
Appearance and finish considerations
- This is a concealed component with no decorative role, so selection questions concern documentation and detailing rather than looks.
- Colour and printed markings vary between products and exist for identification on site, not for any aesthetic purpose.
- Where part of the installation remains visible at a perimeter or an upstand, how it is trimmed and covered is worth agreeing in advance.
- A tidy installation is easier to inspect and photograph, which matters more here than it would for a finish material.
Durability
Durability questions
Questions to raise rather than a service life to expect. No material has a universal lifespan — it depends on the assembly, the exposure and the upkeep.
- How long will the membrane be exposed on site before it is covered, and what protects it in the meantime?
- What happens to the installation if the building is altered later, and who would know that a barrier is there?
- Is the product supported by test data covering the gases identified at the site rather than a general description?
- How do the tapes and collars in the product family behave over time compared with the sheet itself?
- What evidence will exist that the completed installation was continuous at the moment it was covered?
Upkeep
Maintenance and repair considerations
- Who holds the record of where the barrier runs and where its penetrations were formed?
- If a future alteration has to pass through the construction, who decides how the barrier is made good?
- Can any part of the installation be inspected later, or is the construction record the only evidence?
- Is monitoring of the building proposed by the specialist, and if so who arranges and interprets it?
Installation
Installation dependencies
What the installation depends on — not how to do it. Method belongs to the manufacturer's instructions and the trades carrying out the work.
- Installation is specialist work, and the competence and insurance of whoever carries it out is a fair question to ask.
- Laps and penetrations are formed with the components the manufacturer supplies for the purpose, not with general site tape.
- Inspection before covering is the only practical check, so it belongs in the programme rather than in good intentions.
- Weather and surface conditions during installation affect whether tapes and seals adhere as the manufacturer describes.
- Coordination with the groundworks, drainage and services trades has to happen before the work is done, not after.
Documentation
Documentation to request
Ask for these in writing, for the specific product being proposed, and keep them with the project record.
- The manufacturer's test data for the specific sheet, covering the gases relevant to the site assessment.
- The complete component list for the product family, including tapes, collars, top hats and corner units.
- The manufacturer's installation instructions, together with any requirement for trained or registered installers.
- A photographic record of the completed installation, taken before any following trade covered the work.
- The ground gas assessment itself, and the specialist's written statement of what the design is intended to do.
Conversations
Questions for qualified professionals
Bring these to the relevant qualified professional, manufacturer or authority. Requirements vary by project and location.
- Who is taking design responsibility for the ground gas strategy as a whole, rather than for supplying a membrane?
- What does the site assessment require, and how does the proposed approach respond to it?
- Which components of the product family are being used, and are any substitutions proposed?
- How will the installation be inspected and recorded before it is covered up?
- How do the gas barrier and the ground damp-proofing relate to one another in this design?
- What happens if damage is found after covering, and who carries that risk?
- Will the completed work be handed over with a record that a future owner can rely on?
- Does anyone on the team hold a qualification or registration relevant to this type of work?
Blind spots
Commonly overlooked points
- A sheet described as gas resistant is one part of a strategy, and choosing the right roll settles very little on its own.
- Service penetrations are formed by trades who may never have been told that the sheet they are cutting through has a function.
- The record of the installation is worth as much as the installation, because nothing can be seen once the work is covered.
- Substituting a general purpose tape for the manufacturer's jointing tape is a common and completely invisible change.
- Alterations by a later owner can breach the barrier without anyone realising that it was ever there.
What this page does not do
- Ground gas protection is a regulated and site-specific matter. Nothing on this page is a specification, and the design belongs to a qualified specialist.
- No membrane resists ground gas on its own. Resistance is a property of a complete, continuous, correctly terminated and independently verified installation.
- Where a layer sits within a construction, and how it relates to other layers, is assembly design and is outside the scope of a reference entry.
- This entry does not diagnose or treat damp or any other building defect. Investigating an existing problem is work for a qualified professional.
Related entries
Related materials
Materials from the same family, an adjacent role in the assembly, or a shared application.
Inspiration
Related Ideas Library pages
Design directions where this material commonly appears.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this material comes up.
Go deeper
Related Build Design Hub guides
Planning guidance and neutral comparisons behind the decisions on this page.
Sealants & Membranes
Reference entries for the thin control layers — joint sealants, damp-proof courses and membranes, vapour control layers, breather membranes, tanking systems, tapes and foams.
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