Lamyatt Lodge

Project Summary

I&C Developments appointed EPG to deliver a full radon protection design for the redevelopment of historic outbuildings at Lamyatt Lodge, working alongside Concept Eight Architects. The site comprises an 18th-century farmhouse, a 19th-century Georgian addition and three listed outbuildings. It sits within one of the UK’s highest radon potential zones, where full protective measures are required.

The challenge was to achieve modern health protection standards without compromising the architectural integrity of a Grade II listed property. EPG combined geological assessment with a fully detailed, buildable mitigation design tailored to the heritage constraints of the site. The result was a compliant radon strategy that integrated seamlessly with the proposed floor construction and fabric upgrades, giving the project team confidence to proceed with redevelopment while preserving the historic character of the buildings.

Objectives

The project required a complete assessment and design solution to manage radon risk within a sensitive historic setting. EPG’s objectives were to:

• Undertake a geological assessment of radon risk
• Evaluate how proposed floor construction would influence radon behaviour
• Identify appropriate mitigation requirements
• Deliver detailed, buildable design drawings for a subfloor depressurisation system and membrane

The goal was to achieve full radon protection in line with guidance while ensuring compatibility with listed building constraints.

Challenges

• Location within a >30% radon potential zone, requiring full protection measures under national guidance
• Grade II listed status restricting external alterations and limiting locations for pipework and ventilation
• Complex heritage construction including existing stone walls that made perimeter sealing difficult
• Retaining exterior walls affected by damp, requiring integrated waterproofing solutions
• New limecrete floor and recycled foamed glass sub‑base requiring compatibility with radon membranes

Solution

EPG designed a combined barrier and depressurisation system in accordance with BR211 guidance. A sealed loose‑laid membrane was specified as the primary radon barrier, supported by a slotted pipe subfloor depressurisation system installed within the foamed glass sub‑base.

To respect the listed status of the buildings, pipework was routed internally and connected to heritage‑style roof vent tiles, avoiding intrusive external alterations. The system was designed to allow future installation of radon fans within the roof space if monitoring indicates additional attenuation is required.

EPG also detailed lime render finishes and adhesive sealing at wall junctions to reduce preferential pathways for gas ingress. Waterproofing measures were integrated where retaining walls showed signs of damp, ensuring compatibility between moisture control and radon protection.

Results

The results:

• Full radon protection achieved in one of the UK’s highest risk zones
• Heritage‑sensitive design that met listed building constraints without compromising performance
• Clear, buildable technical drawings that gave the project team certainty during construction
• Integrated approach addressing both radon ingress and damp risk
• Future‑proofed system allowing additional ventilation if monitoring requires it

Attribution:

• Developer: I&C Developments
• Architects: Concept Eight Architects
• Radon Risk Assessment and Protection Design: EPG