Restoring a National Icon: Peter Cox Tackles Wet Rot at Edinburgh's Nelson Monument

The survey, carried out by a qualified Peter Cox surveyor, revealed a problem with two vital structural roof support beams that had been severely compromised by wet rot. In addition wet rot was also found in other small sections including the collar supporting the timeball.

Wet rot is a form of timber decay caused by fungal growth in wood that stays damp over time. Though less aggressive than its counterpart, dry rot, wet rot can still cause significant damage if left untreated - weakening structural timber and compromising stability. In historic buildings, defective roofing, damaged gutters, or blocked drains often allow moisture to seep in, creating ideal conditions for wet rot to thrive.

Due to the nature of the damage, Peter Cox recommended repairing the beams using a special strong glue and timber patch called a timber resin splice (TRS).  This technique is especially suitable for historic buildings, as it enables targeted repairs that preserve as much of the original structure as possible, minimising the need for full beam replacement. The treated area can also be expertly blended to match existing timber, ensuring a seamless aesthetic.

The treatment process involved an intricate sequence of steps:

• Cutting Back: The two large damaged beams were cut back to expose solid, healthy timber, removing all decayed material.
• New Beam Formation: Two new beams were formed from machined oak timber, with stainless steel rods resin-anchored into both ends. Oak, a hardwood, was chosen for its enhanced resistance to future rainwater ingress.
• Resin Anchoring: The new beams were lifted into the cut sections, and stainless steel rods were resin-anchored into the four remaining original timber ends. This was then left to harden for a 48-hour period.
• Finishing Touches: Once hardened, the area was sanded down, leaving the new solid oak beams shaped to fit seamlessly with the existing timber. This ensured a smooth blend and improved protection against future water damage.

In addition to the beams, decayed sections of the dome timber collar surrounding the flagpole were removed and replaced with new timber and resin-bonded in place to restore the flagpole’s collar.

Surveyor Rhys Winter reflected on the project: "It was quite an experience carrying out a survey so high up on a historic monument. With the damage to the structural beams, we knew they had to be cut back and sections replaced. Thankfully, with the timber resin splice method, we only had to remove the minimum amount of timber needed to minimise disruption. It was an honour to be part of the regeneration of this monument."

With the wet rot removed the original mechanism built by Maudslay Sons & Field Engineers in 1853, responsible for raising and lowering the time ball, could be safely reinstalled in its newly restored housing.

The successful restoration of the Nelson Monument stands as a testament to the expertise of all members of the project including Peter Cox.

It highlights the importance of timely and specialised intervention in preserving our architectural heritage, ensuring that iconic landmarks, like the Nelson Monument, continue to inspire and endure for centuries to come.