February 2021

14 Buckden Roundabout February 2021 Gatehouse Repair It was the combination of the above factors which caused the tiles and leadwork of the roof to fail, allowing decades of rain to penetrate, saturating the timbers and slowly rot the struc- ture, which led to the collapse of the lath - and - plaster ceiling. Hidden from view by the castellated parapet of merlons and embrasures, the ‘ butterfly roof ’ is constructed with traditional hand - made clay tiles and a central lead valley supported on a pair of timber beams of untreated softwood. The ceiling is vaulted with black decorative oak timbers which frame panels formed of traditional lath - and - plaster. In several places, modern repairs have been carried out using a hard sand - and - cement plaster on metal laths. These were poorly installed, and the heavy panels have started to fall away. There were several design faults within the existing roof. First, the clay tiles were unsuitable for the shallow pitch of the slopes and they had not been properly weatherproofed with lead flashings at the abutments to the surrounding masonry. Many of the tiles had cracked and the bituminous felt under- lay, which was intended to provide a waterproof barrier below the tiles, had torn in several places. Second, the central lead valley was designed to discharge rain- water into a cast - iron hopper at the northern end. However, the use of thin lead in over - long lengths without sufficient ‘ steps ’ across the fall has caused the lead to split, allowing wa- ter to ingress the structure. Over time, the valley boards dete- riorated to create a ‘ hollow ’, further inhibiting rainwater from reaching the outlet. The constant saturation of the roof has also led to the build - up of debris and moss which compounded the problem. In addition to the damaged roof, there are several issues with the brickwork, including loose and damaged bricks to the deco- rative merlons of the parapet, and several deep structural cracks were also discovered and analysed by the structural engineer. Thankfully, the cracks are deemed to be historic. The prove- nance of these cracks is possibly related to the construction of the Victorian cottage and the formation of the associated pe- destrian gate that was formed within the boundary wall, both of which may have destabilised the Outer Gatehouse. The brickwork is a particularly interesting feature of the Outer Gatehouse. On the eastern elevation, within the grounds, the brick has some polychromatic diapering – typical of the Tudor period – which takes the form of diamond patterns made using darker bricks. This continues onto the buttress to the north, confirming that this was an original feature. It is also suspected that a similar buttress was located on the southern elevation and may have been removed when the cottage was construct- ed in the mid - nineteenth century. (Continued from page 13) (Continued on page 15) Rotten timbers and damage to the vaulted ceiling Butterfly roof and parapet brickwork Cracks to the brickwork