Blackburn Cathedral

Porotherm Clay Block Walling System

Project details

Project Name: Blackburn Cathedral Clergy Court
Address: Cathedral Close, Blackburn, BB1 5AA
Date of Completion: May 2016
Contractor: John Turner Construction Group Ltd
Porotherm Product Used: PTH100mm, ZeroPlus mortar
Porotherm Quantities: PTH 100 = 1,450m2 ZeroPlus mortar = 136 bags
Client: Canon Andrew Hindley
Architect: Purcell
Blockwork Contractor: Lambert Walker Ltd

Blackburn Cathedral

Description of Project

This is the first Clergy Court and Cloister garth constructed in the last 600 years. The new building includes: a library; a refectory; a conference room; hospitality suite in the Deanery; offices for the Cathedral and a NW Adoption Agency; an enclosed Cloister garth; an underground car park for 50 cars; 4 town houses for the Dean, Cathedral Canons and Director of Music; 6 apartments for Cathedral staff; 6 shared accommodation units for organ scholars. The Cathedral’s Grade II listing represents its importance as an example of an ecclesiastical building which has grown in stages. It was of major importance in design and selection of materials that the new build retained these principles.

Blackburn Cathedral

Construction Details

Work started on site on 22nd April 2014 with blockwork commencing in April 2015.
The building comprises of a lower ground floor basement and car park with concrete frame up to a podium slab. The ground, first, second and third floor construction comprised of a steel frame system with an external leaf combination of stone, ashlar and 100mm Porotherm with a rendered finish. Roofing is a combination of copper and slate.

Comments from interview with Chris Murphy, Project Manager

This project was never going to be about speed but about minimising wastage and ensuring all material complimented each other. Elevations that contained a mix of façade materials meant that Porotherm could only be constructed in between the programming of Ashlar and stone work construction. However the speed of Porotherm construction was seen on the Dandy Walk elevation where the contractors were under pressure to complete to allow public highway works to be undertaken. This could not have been achieved within the time frame using traditional build methods.

Chris Murphy’s initial concern was how Porotherm would bond in with the large Ashlar units as well as marrying new building techniques with established traditional methods. However as soon as the Porotherm construction started its potential was soon recognised with it being a lot more versatile than initially envisaged. The engineered dimensions of Porotherm was particularly evident when applying the Baumit MP69 render base coat and from an aesthetic point of view the ability to only provide movement joints at 20m centres worked extremely well with the render finish.

The success of the project was in part attributable to the support and guidance given by Wienerberger’s Porotherm Technical team and masons not only at project start but throughout the build. It was also confirmed that customer service from Wienerberger was excellent with all deliveries on time and no issue with lead times. Due to Porotherm’s performance regarding thermal, strength and density, one block type suited all requirements which helped, given storage space constraints on a very tight site. The use of the system’s bagged ZeroPlus thin joint mortar also removed the need for mortar silos.

Lambert Walker, who were using Porotherm for the first time, were also pleased with the product and immediately identified its potential as the elevations mainly constructed out of Porotherm block were constructed extremely fast due to ease of application, the quick setting properties of the mortar and no limitation to build height on each lift. It was also commented that “the build process was a lot cleaner process than usual with no usual mortar droppings” They were also pleased with the ability to use one-handed lifts on the blocks and load scaffold out more than that allowed using traditional concrete blocks.The Client Canon Andrew Hindley quoted

“When Wienerberger Porotherm clay walling system was specified by our Architect, he assured us that this modern building material would work well with the Grade II building the new structure would join onto. It has proved itself very well indeed and has enabled not only a speedier build but also proven how well a truly innovative system interlocks brilliantly with the historic fabric of the Cathedral”.

The Project manager, Chris Murphy further quoted “Given my experience of using Porotherm on this very challanging build, I would have no doubts in using it in future projects for John Turner“.