CONTRACTORS ARE paying out millions of pounds for remedial works on external industrial concrete slabs because consultants are failing to design them properly, specialist contractors claimed this week.
They often have to repair slabs themselves because they are unable to prove that designs are defective without resorting to expensive arbitration procedures.
The newly formed Concrete External Paving Group (CEPG), is campaigning for the immediate publication of up to date guidance on external slab design, taking into account new design techniques.
CEPG claims under-design of slabs has got worse as thinner slabs founded on limestabilised soils have become more common.
Contractors in the £200M a year sector blame structural engineers for poor design.
'As there's no specific guidance on external industrial slabs, engineers try to apply codes and guidance designed for internal slabs or roads, ' said Fosseway Flooring Systems managing director Jan Henning. Fosseway is a founder member of CPEG.
'They insist on low workability concrete and then wonder why there's poor compaction at joints. Or they specify admixtures and cement replacement materials - which increase plastic shrinkage - but only put in joints at 18m centres.'
Henning added: 'Over the last couple of years we've also seen a swing to thinner slabs sitting on lime-stabilised foundations.
There's definitely a significant increase in cracking in these situations.'