Solving Clandon Park’s mysteries with tree rings

Robert Maxwell, Project Archaeologist Robert Maxwell Project Archaeologist
A cross section cut through one of the beams removed from Clandon Park

It’s difficult to believe given its significance, but we don’t have a precise historical record for the commencement or completion date of Clandon Park’s construction. The salvage operation has presented us with a rare opportunity to help solve this enduring mystery using the wooden beams that once formed the skeleton of this grand Palladian mansion.

In the early days of the salvage operation, one of our first tasks was to make the structure safe by removing large pieces of debris from high-level in the building. Amongst the tangled metal and loose brickwork were a number of enormous wooden structural beams. These beams, some 40 feet long, supported the beautiful but very heavy plaster ceilings and roof structure.
Large timbers like these are so dense that they can resist even intense fires without burning through. We were extremely fortunate that some of these beams were remarkably unaffected by the heat. As soon as we saw their condition we thought that it might be possible to use them to more precisely date the house and we knew that our colleagues at Historic England had the expertise in dendrochronology to help us.
One of the giant beams that was analyzed during the dendrochronology study
One of the beams removed from Clandon Park used for dendrochronology
One of the giant beams that was analyzed during the dendrochronology study
Dendrochronology is the science of tree-ring dating. Using this method on the right kind of timbers, it’s possible to accurately date when the tree-rings were formed and so discover when the tree was felled. In the video below the growth rings can clearly be seen in a horizontal cross-section cut through one of the huge beams. Of all the timbers examined so far, three samples had the bark and new growth necessary for the dendrochronology to be successful.
Results have been better than we could’ve hoped for. For the first time we know when and where the trees were felled. We’ve discovered that in either the winter of 1729 or the spring of 1730 a man chopped down a huge pine tree in the cold of northern Europe and within a few short months it was in Surrey, being hoisted up by British builders to construct this amazing house.
An enormous bolt that once held this huge beam in place
A bolt through a fire damaged beam at Clandon Park
An enormous bolt that once held this huge beam in place

The spacing between the rings is mimicked by trees growing together in a particular area. They’re wide apart during a favourable warm, damp growing season but close together when the tree is struggling against cold or drought. We know from experts who’ve studied the growth-rings of similar trees, that half of the Clandon timbers came from Finland and the other half from the Swedish/Norwegian border region.
Historians and scientists who’ve studied the export of lumber in the 1700s think it’s likely that the timbers would’ve been felled to order and shipped from the Baltic soon after. They were probably delivered to one of the many timber yards on the river Thames at Southwark and then made their final journey to Clandon, perhaps coming up the Wey Navigation as far as Merrow. It was common practice to use unseasoned wood because it was easier to work, so we’re confident that the timbers would‘ve been on site at Clandon sometime during 1730. 
Without Lord Onslow’s instructions, architect Giacomo Leoni’s drawings, or bills from the builders, it’s been very difficult to confidently date the construction of the house. With this fascinating discovery we now know that the house was well on the way to being built in the summer of 1730. But a mystery remains; when the Prince of Wales came to dinner in 1729 – where exactly was he eating?

Dendrochronology at Clandon

Hear from our Project Archaeologist Robert Maxwell on this fascinating process. Take a look at the huge wooden beams that were removed from the house and discover how they were used to help reveal more information about Clandon's construction.