Prefabricated house foundations were pioneered in the 1980s by civil engineering group Roger Bullivant. The company developed Tee Beam, a reinforced concrete ring beam, which, as an inverted 375 mm-deep T-shape beam, can span up to 5.5m between precast, driven-steel or CFA piles. Tee Beam can support load-bearing walls with cavities of 5090mm, and the inverted T also offers a nib for cross spanning Bullivant suspended floor systems. It can also carry other proprietary systems.
Tee Beam remains the market-leading precast foundation. But piled foundations are an economic solution only to bad ground. On larger sites with a mix of good and bad ground, developers end up placing two foundation contracts. Now Roger Bullivant is developing an answer for modernising foundations on good ground while also avoiding any cartaway. A small rig piles the ground and creates a cap, which is filled with in situ concrete. A 240mm-deep ground beam, again an inverted T-shape, although this time in stainless steel, is then laid to span between these caps and across the ground in between.
The system is fast - early tests suggest at least a third faster than the Tee Beam that is already one of the fastest solutions available.
Roger Bullivant is continuing to develop the system in preparation for launch in 2005/2006 as part of a package of substructure- and floorslab solutions to be called SystemFirst for Homes. This would include a new insulated suspended floor, again using steel instead of precast concrete to span between the ground beams. Besides speed and the environmental benefit from minimising the dig and removing the need for cartaway, the advantage of SystemFirst is predicted to be less transportation. Quite simply, Roger Bullivant will be able to supply a lot more substructure in one delivery.