Details

How should we treat the edge details on a roof? Over the years a number of different techniques have been developed but none is exactly plug and play. Timber is traditional but getting it fixed correctly at the eaves requires accurate plumb cuts to the rafter feet as well as arrangements for fitting the soffit boards behind the fascia. Gable verges are, if anything, even more time consuming. In recent years some housebuilders have switched to PVC, but although this promises maintenance-free edging boards, it doesn’t make construction any easier.

Roofblock is the work of a civil engineer from Northern Ireland called Andrew Schofield. Its genesis was an attack of vertigo when Schofield built his first home. “It had a timber roof overhang 40 ft up which had to be regularly maintained. I promised myself that on my next house I would design out this chore and eliminate the risk of a serious accident when working at this height,” he says.

The prototype was developed on his second home. He dismissed plastic as a material because it still required a complex timber backing: instead he designed a modular solution in concrete. “As a civil engineer, concrete was a natural choice of material for me to work with. It is both durable and inexpensive, and can be moulded into any shape. For my idea to be readily acceptable on site it had to look like a traditional overhang and had to be easily built.”

The Roofblock system is based on a single section to be used on both eaves and verges. The only other components are three corner pieces which can be adjusted to cope with any roof pitch. There are no mechanical fixings; it’s all laid in mortar. This way the wall to roof junction is finished by the masons before roofing commences, rather than becoming an afterthought for the roof carpenters - as at present. The Roofblock units cope with both cold bridging and eaves ventilation.

Besides the promise of a genuinely maintenance-free detail, the key attraction of the Roofblock system must be simplicity. The house is built as normal until the walls are at the level of the soffit. At this point the corner base slabs have to be set in position, and if there is a gable, the pitch is then set. The blocks themselves can then just be slipped into place on a mortar bed. The only cutting required is a plumb cut at the apex of the gable and maybe one between the corners along the eaves. A fine aggregate is used to produce the block which means that it is easily cut or fixed into. Two builders in Northern Ireland I spoke with were both full of praise for the system. One commented that it helped to have a temporary support batten in place along the bottom edge as the blocks had a tendency to move before the mortar had set. This same builder also reckoned to have saved money using Roofblock when compared with PVC eaves systems.

On the UK mainland, Schofield has licensed Roofblock to Forticrete which sees Roofblock as addressing the Egan report requirement for standardisation, whole life cost and sustainability.

Currently all innovations in the building sector are paying lip service to Egan but Roofblock appaers to deliver.