Dorset House

BACKGROUND

TSL responded to an emergency call out to this student accommodation complex in the centre of Oxford where, following a storm, the building’s façade needed attention. Upon inspection, it was found that the existing timber cladding, and timber support structure, required replacement.

Our priority is always to ensure the longevity of assets and we approached Unite Students to not only address the immediate concerns, but also to future proof their building for years to come. Our in-house design team designed a Class A1 fibre cement cladding system that replicated the look and feel of wood boarding, in a new, fresh grey to match the existing aluminium windows.

Although Dorset House was not classed as a Higher Risk Building under new legislation, our solution enabled the new legislation to be applied to the property.

In addition to replacing the cladding on the two main accommodation buildings, it was also decided to remediate a small, converted house on the site boundary. Here a full fill insulated render system was chosen to keep the look and feel of the adjacent property, whilst improving the thermal efficiency of the property overall.

SCOPE OF SERVICE

Dorset house is a modular POD building. This means that all the rooms are fabricated off site in rectangular PODs, and lifted into place once they arrive on site.

The design process involved fully assessing the existing structure to ensure that the weights of the new cladding system and associated build up, was kept within the design load parameters. The challenge here was to plan how the cladding support structure was laid out across the building façade, to not only keep weight to a minimum, but also allow for adequate support for the new cladding and resistance against imposed loads from the wind etc.

As a consequence, the materials used within the remediation had to have a perfect balance of strength vs weight, be thermally efficient, and cost effective. The list of materials included:

• 9mm thk Kemwell sheathing board
• Obex Cortex EPDM
• Obex 0200FR breather membrane
• RJ Facades EVT Helping Hand & rail aluminium subframe system
• Ryton A1 fire rated vents and steel PPC grilles
• Tenmat ventilated cavity fire barriers & non-ventilated cavity fire barriers
• Rockwool Flexi & DuoSlab insulation
• Hardie VL Plank cladding in anthracite grey including bespoke flashings and feature trims.
• New trims and flashings to existing window & door reveals.

As with every remediation, there were unexpected challenges which had to be overcome. One such challenge was to replace 3 full-height timber nib fins which lacked structural integrity. Our design team created a bespoke SFS frame structure, including bespoke galvanised support brackets, to provide cantilever support to the outer cladding façade.

In addition, the smaller converted house was found to have a very porous masonry substrate. This needed reinforcing with tiebars, new brickwork and in some cases new lintels. This had to be completed prior to the installation of the Alsecco Ecomin 300 render system.