Context

This project involved 36 new affordable and retirement homes, comprising 8 affordable homes for Downland HA and the 28 retirement homes for Bolton Retirement Homes. H+H's Rå Build method was used, with the inner leaf, first floor and roof installed ahead of the external leaf.

Requirement

The homes were required to achieve level three in the Code for Sustainable Homes. The excellent acoustic, thermal and air tightness characteristics inherent with this type of construction contributed greatly towards this. The speed of build was another important factor and the Rå Build method gave impressive time savings over other construction techniques. All the external finishes are of a traditional appearance in keeping with the surrounding area.

Products used

  • 3.6N/mm2 Jumbo Bloks (610 x 270 x 100mm / 115mm thick)
  • 3.6N/mm2 Celcon Foundation Blocks (440 x 215 x 355mm thick)
  • H+H Flooring System (300 x 600mm up to 6.0m long)
  • Celcon Floor edge units (300 x 215 x up to 600mm thick)

Build time

The Rå Build programme for the initial phase of 16 homes from foundations to structural roof completion, took approximately 16 weeks, with some 3,000 m2 of aircrete laid and 900 m2 of the H+H Flooring System installed.

External walls

Cavity construction using H+H Thin Joint system with Jumbo Bloks (610 x 270 x 100 and 110mm thick) and Celfix Thin Joint mortar for the inner leaf, with either brick, flint or clad aggregate blockwork for the outer leaf. With 60mm Kingspan rigid insulation, 50mm residual cavity and an internal finish of 12.5mm plasterboard fixed using dabs, the external walls provided average U-values of 0.21W/m2K.

Separating walls

Two leaves of 115mm Jumbo Bloks, thin-jointed with Celfix mortar. 75mm cavity fully-filled with Isover RD Party Wall Roll acoustic insulation. Finished with 12.5mm plasterboard on dabs both sides. To improve the acoustic performance still further, cavity ties were omitted.

Ground floor

H+H Flooring system with grouted joints. In keeping with the approach of avoiding wet trades and taking advantage of the very flat system, the floor boarding was installed over Kingspan insulation.

Foundations

Strip footings with two courses of Celcon Foundation Blocks to dpc level.

Testimonial

Adrian Rolt, Director at Telegraph Construction Management Ltd, said:

"We were pleased with the Rå Build approach because having the one shell contractor simplified the process for getting the site underway within agreed time frames. The speed of build is remarkable and in fact the watertight shells were ready so quickly we had to be alert to keep up. We found the Thin-Joint walls provide a very solid and true base for following trades”.