Windpost-free blockwork: Tackling the block

Postscript

Innovation and blockwork are two words that do not normally go together. Brick and blocks are specified precisely because they are traditional and unchanging. However, that may be about to change – thanks to a man called Liam Clear who could do for the humble block what James Dyson did for vacuum cleaners.

Clear runs Pyramid Builders, a £10m-turnover London-based brick and blockwork contractor, and is clearly not afraid of a bit of innovative thinking. He has introduced a unique bonus scheme that he says has resulted in a 30% increase in productivity. He has also invented an access system that makes building blockwork walls easier and safer.

Having sorted out staff and tools, Clear has now turned his attention, and £300,000 of his own money, to the product. There was one specific aspect of blockwork walls that really bothered him – the windpost. These are vertical steel posts inserted at 4m intervals in long blockwork walls to give them greater lateral stability.

“There is always a six to eight-week delay procuring windposts,” he says, listing his grievances with the system. “And steel and masonry products are not compatible in terms of contraction and expansion, which necessitates a movement joint. Also, putting a steel post into a masonry wall breaks up the aesthetic value of the wall.” Finally, he adds that windposts also make it harder to pass the Part L airtightness tests.

Clear set about designing an alternative, called the “bond beam”. His idea was to run steel rods horizontally through the wall and anchor these at the corners to give the wall the strength to resist lateral loads.

He settled on commonly available rebar for the steel rods, secured at each end by a specially developed cleat fixed to a steel column. The wall is built conventionally, except without windposts or expansion joints, up to seven courses high. The bond beam is then constructed at course eight.

The rebar sits in special U-shaped blocks made by Hanson. A C40 concrete mix is then poured into the U-shaped blocks to lock them to the rebar. Connecting rods are built into the course below and above the bond beam to lock the structure together. Another bond beam is inserted at course 15, although for walls lower than 3.5m only one bond beam is needed.

The way to prove the idea worked was to compare it with conventional walls – a job that Clear paid testing and analysis firm Ceram to undertake. Lateral loads were applied to Clear’s 8m-long and 5m-high wall. It took a windload of 6.5kN/m2, which according to Clear is more than twice the load walls are usually designed to withstand.

“The results were great. It achieved higher windload capacity compared with standard windposts, the fire integrity was more than what could be achieved with sealants, it’s aesthetically pleasing and forming holes for services is easier,” beams Clear. “Plus there’s a saving of 20% on the construction cost.”

He has patented the system and will either license it to other brickwork specialists or supply and fix the bond beam himself. Contractor Bovis is interested in the system.

Not satisfied merely with solving the windpost problem, Clear has also devised an ingenious way of dealing with two problems that have long affected coping stones at the top of walls: first, that mortar joints often look ugly and, second, that the use of a dampproof course tends to weaken the wall.

Clear has developed a coping stone with a section shaped like a rolling hill cut out at each end at the base. This “female” coping stone is bedded using mortar and a “male” section is inserted to bridge the gap between the two female stones. No mortar is needed between each stone; instead a fine gap is left “to give it the appearance of high quality stone”. A groove is cut into the male section, into which water trickles down from the gap and is carried to the edge of the wall, thus removing the need for a dampproof course.

That should be enough innovation to stand the blockwork industry in good stead for the next few years ...