The old roof consisted of a double-skin steel sheeting system with glass fibre quilt insulation to the original curved wrought iron structure. The large curved roof at both the apex and the main slopes had been formed from double-skin GRP rooflights which were inefficient as ageing had significantly reduced their natural daylight transmittance while insulation to the whole roof needed updating to modern standards.

BDC in conjunction with their architect, Simon Powell, appointed the Letchworth Roofing Company to handle the project as it was felt they had the technical competence, skills and resources to meet the challenges of:

1. Tight time constraints to minimise the disturbance to the BDC’s exhibition programme. All work affecting the inside of the building had to be completed in six weeks.
2. Developing proposals to reduce heat loss, improve the natural daylight within the building and maintain the original building’s overall style to meet the requirements of local preservation groups.
3. The need for a stringent Health and Safety plan to protect all users of the building as well as Letchworth Roofing operatives.

It was agreed that the existing rooflights should be replaced with new factory-assembled triple-skin GRP rooflights and the existing roofing structure overlaid with insulation and waterproofed with a single ply membrane.

FILON Products Limited designed unique curved rooflights for the main slopes incorporating flexible "hinges" where fixed to the purlins. This allowed the rooflights to assume the curvature of the roof and the end result is that the main hall is now lighter and brighter and the rooflights remain “man-safe” for the life expectancy of the new roof covering.

The remainder of the roof has been over-roofed with an insulated single ply system comprising Kingspan Thermaroof insulation board supplied by Encon Limited. This was mechanically fixed to the corrugations of the original roof avoiding the necessity of having to strip off the roof and expose the building to the elements.

A layer of lead grey Sarnafil single ply PVC membrane was then fully adhered to the insulation and lead grey Decor Profile was fixed to mimic the overlap detail found on lead roofs.

Letchworth Roofing completed the project four weeks ahead of schedule and on budget as a result of tight management by Ray Speroni, Major Projects Manager, Dan Tomlin, Quantity Surveyor, and Terry Martin, on site Project Manager.

Business Design Centre Director, Peter Clenshaw, Commented. “Our business is to host major events and be a landlord to a range of design based businesses. Therefore ensuring ‘event downtime’ and disruption to our tenants were kept to a minimum was an essential part of this project, in addition to the construction of a significantly better performing roof. Letchworth Roofing has met all our expectations and we would have no hesitation in recommending them to other businesses with similar requirements.”