WW2 Pitt Bunker Dorset

Case Study / Waterproofing 

WW2 Pitt Bunker, Dorset

Waterproofing the exterior and interior to a WW2 Pitt Bunker

WW2 Pitt Bunker Dorset

Maclennan were given a unique opportunity to design, supply and install waterproofing to the exterior and interior to a Grade 2 listed WWIIPitt Bunker in Dorset.

The structure, which was built in 1939, was one of Churchill’s ‘chain home’ series of bunkers and was used as part of RAF radar sites which looked out over the sea for enemy aircraft.

The final details of the conversion, to a two-bed holiday home, were approved by Dorset Council after gaining listed building consent earlier in the year.

The refurbishment will include internal alterations and finishes upon this monument, as the first part of completing all 5 bunkers in the Ringstead Chain. Due to its new conservation status, there were strict guidelines to adhere to which also needed planning approval.

Pitt Bunker
Pitt Bunker
Pitt Bunker
Pitt Bunker


The structure was cleared of any existing bitumen felt waterproofing, external membrane and encapsulated in a protective water-resistant scaffolding; this protection keeps the site as dry as possible while works are being carried out. It is important to keep areas dry for application of the waterproofing materials.

The British Standards BS8102:22 says you must consider 2 forms of waterproofing if the risk of a leak is high or the consequences of a leak are unacceptable. In this case, application of Hydrogel direct to the concrete was suggested along with a cavity drain system to the internal of the structure.

Hydrogel is the most suitable system for protection of existing concrete structures. It will protect and waterproof. It is a spray applied, non-toxic, 100% VOC Free, environmentally friendly, and economical treatment for protecting reinforced concrete against corrosion and deterioration.

Its unique reactive process, will purge concrete of many contaminating elements, neutralise any remaining contaminants, and seal the concrete against any further ingress of the substances liable to cause deterioration in the long term. Once complete, the Hydrogel will remain effective for the life of the concrete structure.

The cavity membrane system is also fully guaranteed waterproofing of the most vulnerable area. Its plastic membrane with drainage is built into the structure behind walls or linings. the Cavity drain is installed as the serviceable repairable and guaranteed waterproofing system which then ensures compliance with insurer and British Standard requirements.

As this is a buried structure, waterproofing the roof also needed to be considered, the waterproofing system here needs to be extremely durable since it will be buried under soil and landscaping to replicate the original aesthetic of the bunker.

MacLennan specified our Polyprufe system because of Its versatility in cold temperatures, durable properties and hardwearing characteristics. it is specifically designed for use on decks and buried roofs. Protective drainage was then installed on top before covering the roof back over with soil.


The British Standards for waterproofing have recently been updated and Ian Maclennan was a part of the rewriting committee.

We have offered fully guaranteed waterproofing solutions which is in line with the recommendations of BS8102:2022 meaning the bunker is now safe from water ingress. The client can decorate the interior in the knowledge that it will all be protected by the serviceable system.

All works were carried out by our fully qualified technicians and completed within the agreed time frames.

Pitt Bunker
Pitt Bunker
Pitt Bunker
Pitt Bunker
Pitt Bunker


“RAF Ringstead was constructed in 1941 as a Chain Home radar station, and was fully operational by March 1942. Chain Home was a ring of early warning radar stations built around the coastline from the late 1930s and formed an important part of Britain’s Second World War defences. It was the first operational military radar system in the world, using technology developed on the simple principle of ‘floodlighting’ the surveillance area with transmitted pulses of radio-frequency energy. The pulses would ‘echo’ back from any aircraft to the ground station receivers. The range of the aircraft was measured by the elapsed time between the transmitted pulse and the return ‘echo’.”

Pitt Bunker

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