Tags: Design
Complex roof constructed by Harlow Timber Systems for Martha Trust
Posted: Thu, 09 Jan 2014 15:56
An extra care scheme for the over 55s, Hampton Park Hereford is more than just a flagship venture for Martha Trust. It also represents a challenging building project with a complex roof constructed using in excess of 300 timber trusses supplied and fitted by TRA member, Harlow Timber Systems.
The plan of Hampton Park Hereford is circular. A single-storey building, housing one and two bedroom apartments, curves 270° to link with communal facilities which including a well-being facility. At the centre are landscaped gardens and courtyards.
Harlow Timber Systems was asked by B&K Structures, the building contractor for the multi million pound scheme, to devise a roof for the building removing various amounts of steel within the roof complex. Working with the engineer BSP Consulting, it was decided at an early stage to span the radii of the roof with timber trusses.
The roof is formed using dual, preformed mono-pitched trusses set out in a radial pattern on either side of a 2.5m wide flat roofed 'corridor' which accommodates sun pipes to allow daylight into the accommodation below. The trusses measure 8m and 7.5m respectively from external to internal wall plate; spandrel panels are incorporated alongside party-walls.
With the trusses fanning out from 300mm centres on the inner curve to 600mm centres on the outer curve, a key challenge was to bend the bracing to follow the shape of the roof. The external overhang of the eaves was cut short in specific areas allowing raised parapets and inboard gutters to form features of the external elevation. Internally the top-ends of service risers had to be fitted in between the trusses and other mechanical engineering equipment accommodated.
Special steel connectors and a central bracing guide provided support for the flat section in the centre of the roof where it served the same function of a ridge beam in a traditional pitched roof.
Although a very unusual design, this roof is not untypical of the sort of structures Harlow Timber Systems undertakes, says David. "We are asked to engineer complex roofs all the time" he says. "On most projects we spend time with the architects and clients to find a cost saving solution, as we did here. The large span girder on this project is a good example of the sort of structural solution we can provide".