It's been a long journey, but this is conservation on a grand scale and more than just a leaky roof, Drogo's problems were threefold; the roof, the windows and pointing.
The flat roof
Castle Drogo’s medieval-style flat roof has been its Achilles heel. Lutyens had attempted to seal the roof using asphalt, a relatively new and untested material for the time, but it was prone to cracks caused as the temperature rose and fell. Before the building was even finished, it had begun to leak.
The flat roof is roughly equivalent to two football pitches. A high-tech roof system, designed by Bauder was installed. This two layer membrane is designed to cope with the extremes of temperature experienced on Dartmoor.
In order to lay the new waterproof system, 2,355 granite blocks weighing 680 tonnes had to be removed and then reinstated. This involved moving and reassembling entire battlements and large sections of the castle walls.
We also had to redesign the roof gullies to accommodate the heavy Dartmoor rainfall.
There has been a real problem with water penetration through the pointing and around the windows. So the building has been completely repointed. The cracked cement pointing was removed and replaced with an improved lime based mortar. The sheer amount of new pointing required stretches to an impressive 60,000 metres, or 42 miles (laid in a line it would stretch all the way from Castle Drogo to Lundy Island).
The windows have been another major weakness for Drogo. In keeping with a medieval fortress, Julius Drewe had demanded that there were no windowsills, a feature that would have offered some protection from the fierce elements. Every one of the 913 windows has now been removed, refurbished and resealed.
This project would not have been possible without the support of donors, Interreg, the Department for Digital, Culture, Media and Sport and the Heritage Lottery Fund
Proving it works
In 2007 we tested this solution on the chapel, a part of the castle badly affected by water damage. The large windows were restored and the Bauder roof system introduced, the chapel is now watertight.
The house and conservation team completed the mammoth task of cleaning, putting carpets and blinds back and, most importantly, uncovering the collection to return the castle to a family home and bring to life the Lutyens-designed masterpiece, as well as the lives of the Drewe family who it was created for.
During a restoration project of such enormous scale and complexity there have been plenty of surprises thrown at the project team. The unique nature of the original construction and design has required a unique solution to deal with the fabric issues. This impacted massively on the time needed to undertake the repairs.
There were many more construction issues encountered during the work than were expected and the very special kind of weather, only experienced in a location as high and as exposed as at Castle Drogo, has on many occasions prevented work from being carried out.
Truly conservation work on a monumental scale, nothing like it is likely to be seen for a very long time and we’re proud to have made the castle watertight for many years to come.