Kinnaird House, Pall Mall

Overview:

The highly acclaimed project carried out by NDM Lead Sheet Specialists at Kinnaird House in Pall Mall, London, received the ultimate Leadwork accolade by winning the 2001 Murdoch Award.

In presenting the Award to NDM Directors Nigel Miles and Brian Shepherd, Richard Murdoch paid tribute to the consistently high standard of workmanship demonstrated throughout the project, which was a credit not only to NDM and their craftsmen, but to the industry as a whole. He considered it a superb demonstration of what could be achieved in the Leadwork craft and wonderful advertisement fro the LCA.

The work:

The original façade of Kinnaird House was preserved whilst the internal building was demolished and replaced with a new steel frame and concrete slabs. A new mansard roof was constructed by NDM at 5th, 6th and Plant Room levels, complete with Canadian Vermont green slate and including the lead cladding of 55 dormer windows of various types and sizes.

On the 5th floor there was a mixture of pitched and curved tops and on the 6th a more traditional flat roof arrangement. Each of the four corners of the building had identical traditionally slated turrets with four pitched lead clad dormers on each, plus decorative fluted hip and ridge cappings with emblazoned cast decorative ribbons at specified centres. Each side of the dormers were large lead clad scrolled consol brackets.

The slated Plant Room elevations had extensive copings at high level above the finished line of the slates and a scrolled ridge capping with emblazoned ribbon, similar to the turrets.

The outstanding centre piece of the roofscape was a three tiered cupola that had to be completely rebuilt as an exact replica of the original design.

Altogether, some 120 tonnes of Code 5 rolled lead sheet (and approximately 1,000 M2 of random slate) were used on the project which took six months to complete.

This was the second time that NDM had won the Murdoch Award, having previously been honoured for their work at the new education block at Canterbury Cathedral in 1999.
 

The Wakefield Tower at the Tower of London

Overview:

This prestigious project was completed by NDM Lead Sheet Specialists during the first six months of 2004. The installation was carried out to a strict design specification and completed in 12 weeks, using approximately 18 tons of Code 6 and Code 8 sand cast lead sheet.

Historic Royal Palaces made the decision to restore the Tower to its 13th Century appearance, which would include replacing the existing asphalt roof with something that was, in both appearance and methods of construction, to the original design. The architects were able to base their final design on some original Victorian drawings that they were able to source.

The work:

The main circular roof was to take on the appearance of a ‘Witch’s Hat’ when viewed from above. This was to be divided (on section) into three levels, with a stepped perimeter box gutter. The lower and middle layers consisted of 48 bays per layer, with the top layer consisting of 24 bays. On top of the final level, a removable but fully weathered cover was required for the Winching system that controlled the lowering of the chandelier in the main room below. The cover to the chandelier winch was made up of 8 bays.

In pursuit of traditionalism and to virtually eliminate hot works and their associated risks, all lead details were to be bossed, rather than welded. This turned a manageable design into a test of any lead workers skill and only a true specialist would be able to take on such a challenge!

The build process:

The work began with the installation of the main timbers that would support the new substrate. A number of 175mm x 50mm rafters were fitted between the walls of the tower and the centre of the roof area, which created a base for the rest of substrate. Additional rafters were latticed between these main beams to create a solid base for the 100mm x 25mm and 150mm x 25mm timber boards (3mm gap for ventilation). When this substrate base was complete, a three-tiered solid roof had been created and then bespoke sized batten wood rolls were fixed down to create the bay sizes, as per the architect’s design.

A box gutter (with two outlets) was then formed in sawn & treated timber, which was fed from the lowest tier of the witch’s hat. This was stepped every 2.7m (maximum) by a minimum of 100mm to ensure the lead work complied with BS6915.

Lead works began with the installation of Code 8 sand cast lead to the box gutter. The flashing to the box gutter was again sand cast, only in Code 6. However due to the age of the stones, they couldn’t be in any way modified for the installation of the flashing. The lead needed to be installed in the mortar only, which meant that the flashing had to be shaped and installed to follow the mortar lines around the stone. The flashing was installed to maximum lengths of 1200mm between laps. Each semi-triangular bay for the main roof was individually formed on site and installed in accordance with the Code of Practice. This included an up-stand of 100mm between levels, and a splash lap of 75mm to the front of the bay, offering a total weathering of 175mm. All bays were close nailed.