Ipswich is a relatively small town in Suffolk, so the hard landscaping at its heart does not cover a huge area, but it has been designed with consummate care and it has been used to help finalise details for the latest revision of BS 7533. Michael Heap from CED is part of the committee revising the standard and his company supplied the stone for Ipswich. He guides us through the Ipswich project.

BS 7533 is a standard for the design and construction of pavements constructed with clay, natural stone or concrete pavers, precast concrete flags or natural stone slabs. It has developed over 20 years to offer clear, consistent and tested methods for designing and constructing paved areas.

Pavements (a term which includes areas that vehicles drive over) are not always constructed using the standard, which is surprising because for all but miniscule projects the £146 price of the standard (£73 for BSI members) palls into insignificance against the cost of getting the project wrong.

It is not just the civil engineering, either. It is also the aesthetics, although often when it looks right it also performs well.

Getting it right requires commitment from the designer, the stone supplier and the contractor carrying out the work.

In Ipswich, the designer was Graham Rankin from Suffolk Highways, Transport Projects, at Suffolk County Council. CED was the stone supplier from its depot in Essex, one of five it has covering the country. The main contractor was Skanska – and CED has just received another order from Skanska for a complex scheme in Oxford, where the council wanted the same team as in Ipswich because it was so impressed by Ipswich. Skanska sub-contracted the stone laying in Ipswich to PC Caley from Ipswich.

The work on the British Standard will simplify it, condensing the 12 parts it previously had (although parts 10 and 12 were all that were really required for stone design) into two: one for design; one for installation. The project in Ipswich was ideal as a testbed for some of the revisions in BS 7533.

The latest phase of the project is near the bus station, in Dog’s Head Street and Market Street, where a new mini roundabout has been installed.

As with a lot of these projects, stone has been used to elevate the status of the area, to assist in traffic management and calming, and as a way of allowing pedestrians to reclaim from vehicular traffic some element of ownership of the streets.

Although not very large, it was a technically challenging project for a number of reasons.

For example, it has used granite setts that are 180mm deep. Being near the bus station, there are a lot of buses running over these sections of road and it was vital that the roads would be robust, as well as looking attractive.

Buses, because they tend to follow the same line each time, are destructive and BS 7533 recommends the use of 180mm deep setts where a large number of buses will travel over them. CED sourced a red-grey granite that is particularly skid-resistant and the setts themselves will not be damaged by the traffic. But the concrete base has to be competent, all finished off with the excellent Steintec bedding and jointing mortars.

There were 12 manhole covers to accommodate in the granite surface of the mini-roundabout, which has four large quadrants of 205mm thick Chinese granite as its centre – the stone used throughout is either Chinese granite or Italian porphyry for the road surfaces and kerbs and York stone, which actually is from Yorkshire, for the paving.

The Yorkstone has been sourced from various quarries and mixed together, the idea being that if any one quarry ceases production at some point in the future it will still be possible to source matching stone.

The porphyry is a rich violet mix that also includes tones of buff and grey and which is good at hiding staining. It is why it was chosen for an area that includes a taxi rank, so if any oil does leak from the cabs it will not be too unsightly.

The porphyry is laid in arcs and Skanska's subcontractor made a particularly good effort at keeping the arcs working while turning through a curve of no more than 3m radius on the inside. Initially, the various contractors thought it could not be done, but they finally took on board the possibilities when they were shown a photo taken during construction of similar work in Italy. The subbie then put his heart and soul into it to achieve an excellent result.

There is a lot of detail in the mini-roundabout. For example, all the manhole covers have been ‘framed’ properly by the stone, not just set in mortar into an oblong hole in the surface.

The granite setts radiating from the centre of the roundabout are tapered for as much as 5m out from the centre to keep the joints uniform. That is not as expensive as it sounds as long as the decision to do it has been made at the design stage and the stone can be cut in China. Having standard size setts delivered and cutting them to the correct taper on-site would have been too time consuming (and therefore expensive) to have been considered, not to mention the potential for getting the angles wrong.

The setts used for the ramps that rise from the tarmac to the stone surface are also tapered along the line where they meet the horizontal, along the vertical plane. This allows the joints to be a uniform width from the top to the bottom of the ramp, which is aesthetically pleasing and sound from an engineering point of view.

As a prelude to guidance on cutting stone to fit in BS 7533, CED has included a section on ‘Inboard Cutting’ on the technical section of its website (www.ced.ltd.uk). It will be developed further and drawings will be added, but it is worth consulting and CED would be happy to receive constructive feedback on it.

Where curves meet straight lines (as in the picture bottom right here) there can be the problem of small fillets being used to fill gaps. These can be vulnerable and often break out eventually, leading to mortar failure, disaggregation of the surface and the possibility of further failure.

It is easy to overcome by having some oversize setts. But, again, it has to be a consideration at the design stage.

CED offered advice to Graham Rankin about what could be achieved sensibly, technically and economically in the design detail of the stone. Graham says he had not been involved in a lot of stone hard landscaping design before he started working on the Ipswich project. “It was a bit of a steep learning curve,” he says. “Having a company like CED on it has been very beneficial. I have learned a lot.”

Another detail is the raised granite kerb at bus stops, with the granite having a curved profile down to the road to allow the buses to pull in close to the kerb and provide level access for anyone who has difficulty negotiating a step, such as wheelchair users.

In another area, a visual inspection of the area to be paved before work started clearly identified where barrels of beer were being dropped on to the pavement for deliveries outside a club. There are hatches in the pavement leading to the beer cellar.

There was not much that could be done about the deliveries as there was no other access to the cellar, but there was something that could be done to stop the Yorkstone paving from cracking under the impact – simply use thicker stone. So at that particular point the paving slabs are 150mm instead of the 75mm elsewhere.

CED first worked in Ipswich in 2010, when it supplied the hard landscaping for the Buttermarket area of the town (pictured on pages 16/17). That involved relocating the statue to cartoonist Giles, perhaps the most famous son of Ipswich, by local artist Miles Robinson. It had previously been on a base of brick. The design raised it on to a plinth of granite, which also acts as seating.

Around the statue is Yorkstone paving in widths from 400mm to 600mm in 50mm steps and random lengths. It is quite fashionable to design paving like that these days but CED were using it in this way long before it became fashionable. Areas to be landscaped are often in irregular shapes and these different sizes of paving allow flexibility for dealing with awkward detailing. It is also economical and sustainable because it allows the quarry to achieve more finished product from each block of natural stone.

Another part of CED’s contributions to the town is a compass in the sandstone paving on the waterfront. Produced in pink quartzite and green and grey Cumbrian slate two years ago, it remains in pristine condition, in spite of the evidence of some abuse in the paving that surrounds it. It is once again thanks to the design detail, as well as the resilience of the stone itself, that it has survived so well. It has been carefully thought out to avoid elements that are too fine and could break off.

There are lessons to be learnt from all projects, but so they do not have to be re-learnt at every project, BS 7533 is to be commended to both designers and contractors.