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Conservation at Castle Drogo

Green hills and Dartmoor landscape in the background with top section of the Drogo roof visible in the foreground. Light colored granite stone with steps leading up to a higher section of the roof.
View from the roof after the building project | © James Dobson

Following nine years of major conservation work, the ambitious project to save Castle Drogo was completed in 2021. Find out more about the project that found solutions to stop leaks across the roof, the windows and all of the pointing. Discover how the project was supported through generous donations.

A very special castle

English architect Sir Edwin Lutyens designed Castle Drogo, the last castle to be built in England. The work took 20 years and finished in 1931. Julius Drewe had commissioned the work to make the castle his family home in Drewsteignton on Dartmoor. Sadly even before it was finished the building had already started to have issues due to a mix of problems arising from the design and the location.

Why a major project was required

A project was needed to address nearly 100 years of water ingress, leaks and damage. Find out more about the challenges faced by this historic castle perched on the granite out rock on Dartmoor now that the project is completed, by reading through the project timeline below.

Key stages during the project

The flat roof

Castle Drogo’s medieval-style flat roof was leaking even before the building was completed. Lutyens had attempted to seal the roof using asphalt. This was a relatively new and untested material for his time. The asphalt was prone to cracking caused when extreme temperature changes take place.

A new waterproof solution

The size of the flat roof is roughly equivalent to two football pitches. This needed a high-tech roof system to keep it waterproof. The work included installing a two layer membrane system. The new roof system is designed by Bauder who specialise in waterproof roofing solutions. The new material will cope with the extremes of temperature experienced on Dartmoor.

The conservation project showing granite blocks removed from the walls at Castle Drogo, Devon
The conservation project at Castle Drogo, Devon | © National Trust Images/Chris Lacey

Removing granite block slabs

In order to lay the new waterproof system 3,500 granite blocks, weighing anything up to 1.4 tonnes each had to be removed and then reinstated. This involved moving and reassembling entire battlements and large sections of the castle walls.


There had been a real problem with water penetration through the pointing and around the windows. The mortar holding the windows and granite in place had cracked and was letting in water. To achieve a good seal the team needed to remove the cracked mortar from around every stone.

Using lime mortar

The new pointing was made from an improved lime based mortar. This new mortar allows the building to breathe and is frequently used in historic buildings. The sheer amount of new pointing required stretched to an impressive 60,000 metres.

The windows

The windows have been another major weakness for Drogo. In keeping with a medieval fortress, Julius Drewe had demanded that there were no windowsills. This feature that would have offered some protection from the fierce elements seen on Dartmoor. 913 windows were removed, refurbished and resealed.

Making the chapel watertight

In 2007 the windows were replaced in the chapel. This part of the castle badly had been affected by water damage. The large windows were restored and the new Bauder roof system installed.

The roofscape and original asphalt of Castle Drogo, near Exeter, Devon
The roofscape and original asphalt of Castle Drogo, near Exeter, Devon | © National Trust Images/Andrew Butler

Challenges to overcome

During the complex project there were plenty challenges for the team to work through. The unusual nature of the original construction and design has required unique solutions. This impacted massively on the time needed to undertake the repairs.

Extreme weather

There were more construction issues encountered during the work than were expected. Plus the weather in this high and exposed location has on many occasions prevented work from being carried out due to extreme high winds and heavy rainfall.

Thank you for your support

We’d like to thank everyone who supported the project through donations and by visiting during the project to see the work in action.

This project would not have been possible without the generous support of several donations. We would like to thank:

  • Interreg
  • Department for Digital, Culture, Media and Sport
  • National Lottery Heritage Fund
  • Belsize Charitable Trust No 1
  • Moira Black and Robert Gurd
  • Mr Paul Byles
  • Mr J A Douthwaite
  • Steve Edge
  • Andrew Fletcher OBE
  • GMC Trust
  • Hargreaves and Ball Trust
  • The Headley Trust
  • Historic Houses Foundation
  • The Ironmongers' Company
  • Martin Lutyens and The Lutyens Trust
  • The Norman Family Charitable Trust
  • The Royal Oak Foundation
  • The Partners of Slaughter and May
  • Eleanor Redgrave and the staff, volunteers and supporters of Castle Drogo
  • The Wolfson Foundation
  • Richard Allan Wallis
  • John Laurence White
  • Annette and Terence O'Rourke
  • And all those who left a gift in their will to this special place
  • Donors who wish to remain anonymous
Two visitors admiring the view over the countryside from the roof at Castle Drogo, Devon


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