Robinson Court, St Elphin's Park - Forticrete

British Precast Best Practice Awards 2014
Project Award: Robinson Court, St Elphin's Park

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Audley St Elphin’s Park is a luxury retirement village set within 14-acres of landscaped grounds on a 44 acre site in Darley Dale, Derbyshire. The centrepiece of the luxury retirement village is St Elphin’s House, built from natural stone in the 1820s. For the construction of Robinson Court, a development of 20 one and two bedroom apartments, planning requirements dictated that the external façade be built from natural stone reflective of that of St Elphin’s House.

Forticrete provided a truly innovative concrete-based alternative in its purpose-made cast stone Regency Ashlar blocks that seamlessly replicated the colour, size and texture of St Elphin’s House, at just a fraction of the cost. Forticrete’s beautifully crafted stone detailing including decorative heads, cills, plinths, string courses, copings and finals were also used to replicate the tradition, quality and aesthetic appeal of the existing natural stone of the existing buildings.

The local planning authority was unanimously impressed with the resulting finish. So much so, they openly admitted how difficult it was to truly differentiate between the natural stone of St Elphin’s House and the high quality finish of the cast stone of Robinson Court.

Audley St. Elphin’s Park also consists of two earlier development phases; Hamlet & Chapel Mews – a selection of two bedroom cottages, apartments and Thornton Mews – a selection of four luxury mews cottages, both of which incorporate Forticrete’s popular Anstone walling stone and its cast stone Regency Ashlar blocks.

RESPONDING TO LOCAL CHARACTER
Due to the prominent location of Robinson Court within St Elphin’s Park, the local planning authority were adamant that the main body of the external skin impeccably complemented the heritage and importantly, the natural stone finish of St Elphin’s House.

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With the introduction of the National Planning Policy Framework (NPPF), which places significant importance on the need for planners to be more open-minded to new, innovative alternatives, which are just as capable of ensuring high quality design; Forticrete proposed Robinson Court be built using cast stone.

FUNCTIONAL SUITABILITY
Forticrete invited representatives of both Audley and the local planning authority to its Masoncrete manufacturing facility. The company highlighted how cast stone can be comparable to natural stone in both appearance and performance, yet it is readily available and provides a truly cost-effective alternative, that thanks to its strength and durability is capable of standing the test of time.

The company also educated both parties on its innovative manufacturing processes which enabled blocks be formed to bespoke shapes and sizes and can surpass the technical capabilities of natural stone in terms of strength, moisture penetration and colouring.

Both Audleyand the local planning authority were unanimous in agreement that Forticrete’s cast stone Regency Ashlar blocks provided the ideal solution for projects such as Robinson Court, where sensitive planning constraints and natural stone is a predominant building material.

USE OF CONCRETE IN COMPOSITION, STRUCTURE OR FORM
The perfect example of advanced technology and time honoured craftsmanship working together in perfect harmony, Forticrete’s Regency Ashlar is manufactured from high grade limestone and sandstone aggregates that have been chosen for their known performance and reliable quality. It is created from a homogenous mix, without using a ‘backing’ material that ensures no undue stresses are built up within the unit.

The company uses a sophisticated curing method whereby it is prematurely aged to improve early handling and to reduce efflorescence on the product surface. This is thanks to a generator, fired by propane, which mixes its resulting combustion gas (essentially carbon dioxide) with air and water. This mixture is introduced to each curing chamber via ducting by controlling both time and temperature of flow. This process is 40% - 60% more efficient than a conventional boiler in energy generation alone.

Furthermore, the carbon dioxide in the vapour reacts with the calcium hydroxide solution formed to precipitate calcium carbonate under the surface of the concrete; increasing density and compressive strength in less time and reducing efflorescence. To further increase the density and compressive strength of its cast stone products, Forticrete also use mechanical compaction hammers to compact the product, the only UK cast stone manufacturer to do so.

WORKMANSHIP AND FINISH
After an initial site visit, it was clear that the smooth face of traditional 'ashlar' blocks didn’t reflect the finish of the natural stone of St Elphin’s House. Therefore over a number of additional site visits, Forticrete took wax rubbings of the natural stone of St Elphin’s House. These were then fed back to Forticrete’s product development team to create a unique ‘mason tooling’ finish for the face of the Regency Ashlar block. This was achieved using resins and a purpose made jig and comb to create over two hundred individually marked mould boards. The resultant Ashlar blocks were found to successfully replicate the texture of the natural stone of St Elphin’s House.

To further imitate the construction of St Elphin’s House, Forticrete also ensured the blocks were made in a number of bespoke sizes up 600mm in length built in three different height courses combined with narrow 5mm mortar joints.

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TESTIMONIAL
“Due to the prominent location of Robinson Court and proximity to St Elphin’s House within the Audley village, there was a desire for natural stone to be used for its construction. It was essential we specified a natural stone product best suited to fulfil the local planning authority’s desire for Robinson Court to sit seamlessly within its existing natural stone vernacular.

However, we were looking for a cost effective, yet sensitive alternative to natural stone for use on this site. Forticrete’s unique colour matching capability and ability to replicate the texture of the natural stone meant Forticrete’s Regency Ashlar provided the ideal solution, boasting the same architectural properties as natural stone, with an aesthetically pleasing finish at a fraction of the cost.

“The design team were unanimously impressed with the end result; the high quality of the finish makes it difficult to differentiate between the natural and cast stone.”

M2H Architects