St Cross Building, Oxford

Project: St Cross Building, Oxford

A 45 years-old Grade II* building is being preserved for posterity with input from Z-Led.

St Cross Building Oxford is home of the Law Faculty and Bodleian Law Library. Its 45+ years-old buildings feature a copper roof now needing refurbishment, and upgrading to modern standards.

Building surveyors/ project managers TMD wanted to minimize impact of the upgrade, devising a solution that included installation of Z-Led HTR cavity trays below the line of the atrium roof.

London Wall Masonry removed the top three courses of brickwork below the roofline, and inserted the HTR trays as part of the project, which included stripping off the existing roof coverings, renewing the roof deck and fitting new insulation and copper roof coverings.

Commented Charlie Biggers for TMN, “As the building is Grade II listed, we wanted the refurbishment to be as close to the existing as possible; Z-Led colour-matched the HTR trays to the copper roof, helping achieve the least impact on visibility post construction.”

“There was no cavity tray in there at all initially,” added London Wall Masonry’s Tony Forward. “We felt it was essential to include a damp proof course to optimize roof longevity, and looked at a couple of options but decided Z-Led’s HTR gave us easier installation.”

Z-Led HTR cavity trays are specifically designed for ease of sequential installation, being a standard 2½ brick length. Contractors simply remove sections of the course of brickwork, insert the HTR Refurbishment Tray, and replace the bricks, working along the course as required. The tray is designed to accommodate cavities of varying width, from 50mm upwards, without the need to build into the inner leaf.

To further help simplify the process, Z-Led manufactures internal and external corners and handed stop-ends. Each HTR tray includes an integral bedweep, which saves the need to add weepholes- a process often overlooked. Once installed, the trays slightly project from the wall, giving a neater finish and simultaneously reducing the risk of the dpc being pointed over which can create a bridge for damp.

HTR Refurbishment Trays are just part of Z-Led’s comprehensive range of materials to defend buildings against damp and gas penetration, and optimise fire protection. Part of the Building Product Design Group, Z-Led ( specialises in developing innovative yet practical solutions to meet changing demands in its specific markets.