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.

[Caroline]

Hello

 

I am also building a single storey house.  Our building control drawings showed DPC to be Radon type.  Building control officer visited this week and asked for a Radon report (planning didn't).  We have spent so much on various reports including a contamination report (part of our planning conditions) but that didn't test for Radon.  A previous report from a couple of years ago suggested Radon would be less than 3% but BC wasn't satisfied with this (probably because it was a couple of years old).

 

I suggested to building control that we pay for the Radon type DPC which will probably end up being cheaper than getting another report/time etc.

 

The reports needed to be produced nowadays cost a fortune, drives me mad.

 

All the best

[Oz07]

I've been saying the same thing. It's ott

[kandgmitchell]

Ask the BCO if a Radon Georeport on the site from the British Geological Survey would be sufficient - they cost £55.44 inc vat. You just need a postcode or national grid reference, order on line and get a pdf back within two days. It complies with BR211 so should be sufficient for them.

[Redbeard]

In 2022 I paid £3.90 for a radon report from BGS. 

 

Among other things it said:

 

 Is this property in a radon Affected Area? - No

 

A radon Affected Area is defined as where the radon level in at least one property in every hundred is estimated to exceed the Action Level.

The estimated probability of the property being above the Action Level for radon is: 0-1%

 

Guidance for new buildings and extensions to existing properties What is the requirement under Building Regulations for radon protection in new buildings and extensions at the property location? - None

 

BCO accepted this.  I did not have to take any measures at all.

[DevilDamo]

On 06/06/2025 at 16:51, kandgmitchell said:

Ask the BCO if a Radon Georeport on the site from the British Geological Survey would be sufficient

What jurisdiction does the BCO have over a Planning condition?

[ETC]

Madness. If there’s radon in the place where you are building put down a radon barrier. Why do you need a report to say that one is needed.

 

Either a 1200 gauge membrane UNDER the slab or a radon proof DPC (Visqueen CPT) sealed to the DPM to the perimeter of the dwelling ABOVE the slab. If you need a sump - put one in - what is so complicated about this - I see it every day. If you want a detail let me know and I’ll post one.

[DevilDamo]

10 hours ago, ETC said:

If there’s radon in the place where you are building put down a radon barrier

That is why the Planning condition is there, to assess the site for any potential. If the assessment deems there is no risk, then that will save the OP a lot of money on the build cost.

[dpmiller]

15 minutes ago, DevilDamo said:

save the OP a lot of money

really?

[newbuild upnorth]

we are in a radon area and BC basically specify radon barrier for all houses, which isn't a big deal as you are generally putting a dpm down anyway so its just the added expense of a radon dpm.

I know its a pain but id be inclined to get the report signed by whoever it is that is qualified to interpret the same report you can buy online.

it would be serious if further down the line a radon barrier dpm wasn't enough and some other standard wanted sumps or something more.

[Temp]

11 hours ago, ETC said:

Madness. If there’s radon in the place where you are building put down a radon barrier. Why do you need a report to say that one is needed.

 

Presumably it's to show that ONLY a simple barrier is needed.

[kandgmitchell]

13 hours ago, DevilDamo said:

What jurisdiction does the BCO have over a Planning condition?

None, I'd got distracted by references to BCO's in other posts.

 

However, I would say that the National Building Regulations do require reasonable precaustions to be taken against risks from contaminants such as Radon. Why a planning authority feels it needs to get involved in such technical matters surprises me. Given an LPA covers a specific and limited geographic area it should know whether Radon is a particular risk, and if it is then by all means put an advisory on the permission but leave it to those qualified who will check the design for compliance both on paper and on site to deal with it.

[ETC]

3 hours ago, DevilDamo said:

That is why the Planning condition is there, to assess the site for any potential. If the assessment deems there is no risk, then that will save the OP a lot of money on the build cost.

Rubbish. It’s the cost of a 1200 gauge DPM with all joints sealed and a few top hats. Put it under the slab and you don’t need any radon proof DPCs at all.

[ETC]

3 hours ago, Temp said:

 

Presumably it's to show that ONLY a simple barrier is needed.

If the radon maps says there’s radon in the area put a radon barrier down. What benefit is spending a shed load of money on an “assessment” which will more than likely be a desktop exercise using the same maps!

[Oz07]

14 hours ago, ETC said:

Madness. If there’s radon in the place where you are building put down a radon barrier. Why do you need a report to say that one is needed.

 

Either a 1200 gauge membrane UNDER the slab or a radon proof DPC (Visqueen CPT) sealed to the DPM to the perimeter of the dwelling ABOVE the slab. If you need a sump - put one in - what is so complicated about this - I see it every day. If you want a detail let me know and I’ll post one.

Post the detail. Be handy to have around. 

[ETC]

I’ll do it tomorrow when I’m at work.

[DevilDamo]

Without an assessment and if the OP decides to commence works, then they will be in breach of the Planning approval. Simple.

 

The OP could decide to vary or remove the condition, but would need to provide the LPA with sufficient evidence to back it up.

 

An assessment can be carried out and it may prove there is little to no risk, then happy days. The LPA would not have included the condition if they didn’t have some information to back it up.

 

All pre-commencement conditions are (should be) discussed with the applicant and/or agent prior to being included and issued. It would have been at that time for the applicant and/or agent to query the requirement with the LPA.

 

Without a suitable site investigation and/or contamination report, the OP may struggle to take out any new build warranty on the new dwelling. Even more crucial when trying to borrow money or secure a mortgage against it.

 

A warranty provider (i.e. NHBC) will request a complete radon protection if there is no site investigation and/or contamination report. This will also include barrier pipe.

[DevilDamo]

10 hours ago, Oz07 said:

Post the detail. Be handy to have around. 

You will find plenty here…

 

https://visqueen.com/technical-downloads/#detail-library