Radon gas risk assessment condition

[flanagaj]

One our conditions is for a Radon gas risk assessment.

"No development shall commence on site until a radon gas risk assessment has been submitted to and agreed by the Local Planning Authority. This should conclude whether a gas impermeable membrane needs to be installed into the buildings to protect the future occupants of the development. If a gas impermeable membrane is required then details of this should be submitted along with details of the ventilated sub-floor area. Particular attention to joins with any existing structures and seals around any services, should be submitted to and agreed in writing by the Local Planning Authority. Any services entering/leaving the structure shall be located above the gas impermeable membrane, and adequate seals will be provided to ensure the membrane is not breached. The works shall be undertaken in accordance with the approved details. REASON: To ensure that adequate measures are taken to avoid the potential risk to future occupiers from natural gases arising from the ground"

 

If I look at the Radon map in relation to our site.  The plot sits within a 3-5% risk and the neighbouring areas are 5-10%.  There is nothing on the map nearby that is > 10%.  The LABC states that 3 - 10% can be achieved as follows.

What is basic radon protection?

Where the radon potential band is between 3 - 10%, basic radon protection should be provided when constructing new buildings, extensions and conversions.

Section 5.1 of BR 211 contains guidance on how to achieve basic radon protection. However, in general terms, basic radon protection may be provided by installing a cavity tray that is continuous with the damp proof membranes (DPM) in the floors and damp proof courses (DPC) in the walls. 

This will prevent radon entering the building through the cavity. Sealing of joints in the membranes and sealing around service penetrations are also required. It is important that attention is paid to detailing and workmanship in jointing of the membranes. If good standards of design and workmanship are applied to the provision of a 1200-gauge DPM to the floor and sealed to a DPC/cavity tray through the walls, adequate protection from radon will likely be provided along with the general function of excluding moisture. 

It is also important that all materials, which are to be relied upon to provide protection from radon entering the building, are suitable for the intended purpose and installed in accordance with the manufacturer’s recommendations. 

 

As a result, can I just satisfy the condition by supplying the image below and stating that it simply requires basic radon protection which will be achieved by Section 5.1 of BR 211, or are they physically wanting someone to do actual measurements on site?

[flanagaj]

Not sure why I posted this.  ChatGPT seems to be pretty confident.

 

Thank you, Justin — this is very useful and confirms that you do not need a specialist radon consultant for Condition 25, provided that:

1. You are following the basic radon protection measures as outlined in BR 211 (2023); and

2. Your builder or Building Control will oversee the correct installation of the membrane and associated detailing.

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✅ Summary: What You Can Do

Since your site falls into the 3–10% radon probability zone, you only need to provide basic radon protection as part of your build — not full radon mitigation.

You can discharge Condition 25 by submitting a short statement confirming the following:

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📝 Radon Protection Compliance Statement (Draft Text)

Radon Gas Risk Assessment – Condition 25 (24/02890/FUL)

In line with the UK Health Security Agency’s radon maps, the site at Former Cattery, White Lane, Hannington, RG26 5TN falls within a 3–10% probability zone for radon. As such, the development will incorporate basic radon protection measures as set out in Section 5.1 of BR 211 (2023).

These include:

• A continuous 1200-gauge damp proof membrane (DPM) installed across the ground floor slab;

• Sealing of all joints in the membrane and around service penetrations in accordance with the manufacturer’s instructions;

• Integration of the DPM with the cavity tray and damp proof course (DPC) to create a continuous barrier;

• Quality workmanship to ensure air- and moisture-tight seals.

All works will be completed under the supervision of Building Control and in accordance with the recommendations of LABC and BR 211, ensuring compliance with both Building Regulations and the planning condition.

Signed:

Applicant and Self-Build Project Manager
Date: [Insert today’s date]

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Would you like this formatted into a formal PDF/Word statement for submission? I can also include a reference to an example DPM product if you’re using one.

You said:

Will that satisfy the condition or do you think they are wanting a consultant to take measurements on site of the actual Radon levels

ChatGPT said:

Your concern is entirely valid — but based on the wording of Condition 25 and your site's radon classification, you should not need a consultant or on-site radon testing. Here's why:

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✅ Why the Draft Statement Should Satisfy the Condition:

🔹 1. Condition 25 Wording:

"No development shall commence on site until a radon gas risk assessment has been submitted to and agreed by the Local Planning Authority. This should conclude whether a gas impermeable membrane needs to be installed into the buildings to protect the future occupants of the development."
(…If a gas impermeable membrane is required then details… should be submitted.)

This clearly allows for:

• A desktop risk assessment; and

• A practical conclusion based on the mapped risk and BR211 guidance — not site gas testing.

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🔹 2. Your Site is in a 3–10% Probability Zone

According to UKHSA radon maps, your site falls in a basic protection zone, which:

• Does not require detailed gas monitoring or mitigation systems;

• Does require a well-installed DPM integrated with DPC — a standard build element.

The Local Authority Building Control (LABC) statement you quoted explicitly confirms that basic radon protection is sufficient in these zones when standard good practice is followed.

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🔹 3. National Precedent and Practice

For self-builds in low- to moderate-risk radon areas:

• Councils typically accept a signed design compliance statement referencing BR211, provided it includes:

  • The mapped risk band

  • A description of the construction measures

  • A declaration that these will be implemented

Site testing is only expected in high-risk (10–30%) or very high-risk (>30%) zones or where there's suspected radon ingress during or after occupation.

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⚠️ Just One Caveat:

Some councils will come back asking for confirmation from Building Control or a contractor that the membrane was installed correctly. You can defer that part to a completion stage if necessary.

[DevilDamo]

An assessment will need to be carried out by a specialist. ChatGPT will not cover you should any issues arise in the future, let alone satisfying the requirements of new build warranty providers.

[flanagaj]

1 hour ago, DevilDamo said:

An assessment will need to be carried out by a specialist. ChatGPT will not cover you should any issues arise in the future, let alone satisfying the requirements of new build warranty providers.

I am going to submit the document.  The condition did not clarify a physical site assessment.  

 

[DevilDamo]

2 hours ago, flanagaj said:

The condition did not clarify a physical site assessment.  

 

I never said it had to. The condition requests the submission of an assessment to be approved by the LPA. If the LPA do not have their own in house environmental or scientific officers, then the assessment will be sent out and reviewed by an external consultant. The assessment may well end up being a desktop exercise but by a specialist.