15th October 2020

New Blocks and Extensions

The steel frames of the new blocks are quickly erected by Mifflin, with the pre-cast concrete floor planks and staircases swiftly following on to provide safe working access to each level.

As soon as the planks are in place and the structural toppings cast, DCL start installing the light-gauge steel infill wall panels, floor by floor, with the intumescent fire protection first being applied where necessary. The external sheathing of cementitious board provides the designated air-tightness line, and each board is carefully sealed to its neighbour with specialist air-tightness tape (white in the picture).

The logical simplicity of the two teaching blocks is apparent inside, with the zones for the teaching spaces north and south of the generous central corridor. With temporary film taped over the windows, and the felt AVCL on the roofs, the teaching blocks become reasonably waterproof, allowing the drylining and boarded fire protection works, also by DCL, to start in earnest.

The sports hall’s tall volume is being created with composite panels which suits its scale and simplicity – as it has almost no windows – and provide good airtightness and insulation.

As the massing of the new blocks takes shape, the scaffold is steadily extended all over C stations facades to provide access for Concrete Renovation’s masons, to physically check all of the historic brickwork for the programme of external repairs and repointing. This work is an essential complement to the internal lining works, as it is very important that as little water is absorbed by the old walls as possible, and that all the historic elements are shedding water as they should. Happily, we find that generally the brickwork is of excellent quality, with only localised repointing required, even at high level.

The most complex adaptation is within the Transmission Block, at the interface between the old walls and the new top floor. The parapet, which was rebuilt after the 1944 fire, turns out to be distinctly different than anticipated, with a residual cavity within the long walls and much thinner end walls. All the details need to change, with an insulated composite panel wall being installed behind the historic brickwork and fixed back to the new steel frame at the top, to form the new top floor.

This requires a series of careful details to prevent water ingress and manage the thermal and air-tightness continuity across the junctions, including where the panels need to incorporate steel posts on the slender end walls, set behind rigid insulation and insulation sealant and sealed before the cover plate is installed.

Sadly, the planned topping out ceremony is off because of Covid, but the view from the new roof over to the first phase of Houlton, shows how the School will sit at the centre of the new community as it is gradually brought to completion.

At the end of October we take our colleagues from the DfE and their technical advisor team around the site, which is generally very positive, with all appreciative of the quality of the work, and the progress made by Morgan Sindall, and their team, despite the delays caused by lock-downs and related delays to materials supply.