Conservation works to (a) repair a metal flat roof and (b) limewash the external elevations of the building

Tender description

In the 2007 refurbishment, a standing-seam copper sheet flat roof, with relatively shallow falls, was installed over the early-eighteenth century central staircase area. There are issues with standing water leading to local water ingress through the joints, staining of ceiling in two locations. It is proposed to replace it with new lead sheeting laid at improved falls. A temporary roof will be erected over the entire return during the works. The copper finish together with its plywood substrate will be stripped back to allow a full inspection of the roof. The condition of the roof timbers will be assessed, with allowance made for some spliced repairs. The slope of the roof will be adjusted through the introduction of sloped timber firring pieces along the top of the rafters. A new plywood deck will be installed, with provision for a valley gutter falling to the existing hopper outlet; to be followed by the installation of a lead sheet roof to LSA good practice details. The insulation of this flat roof will be upgraded with hemp batts as part of this work. The external traditional lime render finish dates from the 2007 refurbishment of the Bishop’s Palace. The lime wash finish was last renewed in 2013. A further durable lime wash coat is now required to best international practice standards for exposed facades.