Dunsmore House

Set in the Scottish Highlands, this small development tests and measures the performance of local timber and modified wood in a challenging environment.

About this project

Set within a south-facing woodland site at Ardross in the Scottish Highlands, some 30 miles north of Inverness, the semi-detached, larch-clad building was designed as a self-build for two families, with each home’s open-plan living accommodation placed at first floor level to gain maximum solar benefit and to facilitate distant views.

Use of local timber

Designed and built by Neil Sutherland Architects/MAKAR Ltd., this combined architecture and construction company produces (almost exclusively) ecological homes that are predominantly manufactured from locally-grown timbers such as Douglas fir, Scots pine, Scottish-grown larch and Sitka spruce. The company has also developed its own heavily insulated, closed panels that are designed work in conjunction with the large-section, platform timber frame structural system MAKAR prefabricates in its own workspace near the Highland capital.

Service areas and bedrooms are located on the ground floor. In order to have minimal impact on the land, each house is supported on eight shallow pad foundations from which concrete posts project to support ground beams. These longitudinal timber elements are well-protected from rain but, although the risk of permanent wetting leading to decay was relatively low, concern that seasonal shrinkage and swelling of the beams could affect the level of the building led to the development of glue-laminated beams made from acetylated timber.

Measured against performance

A small, low-tech research and development exercise formed part of the design and construction of Dunsmore House.

Once installed, the Accoya® beams underwent an extended period of monitoring by Edinburgh Napier University’s Centre for Offsite Construction and Innovative Structures (COCIS), using strain gauges to assess whether any settling over time had taken place. The results indicated good performance with virtually no movement, the conclusion being that the acetylated ground beam solution could be used beneficially in many instances instead of the continuous strip foundations that are the norm for so much of the housing built in the UK today. Not only would this offer considerable economies in time and construction materials, but potentially also save some 2000 Kg carbon dioxide EQ per house, a massive reduction in the sector’s impact on the environment.

Product innovation for enhanced durability - Accoya

Accsys Technologies PLC have continuously explored innovative applications for the acetylation process that look beyond cladding and decking solutions. The Netherlands-based group has been instrumental in pushing forward new options and possibilities for its particular version of modified timber, including testing the material’s long-term durability and general performance in lining canal walls and in a range of large and small bridges in the Netherlands that are in direct contact with water. 

Further information

The Modern Timber House in the UK, chapter 4; 

Take a closer look at modified wood.

Find out how to specify modified wood.

Images: MAKAR

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