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Fir exchange

Structures Timber engineering

A showcase for Scottish home grown timber is taking shape on the Firth of Forth. Dave Parker reports.

Even on a grey, damp October afternoon when NCEI visited, the bare skeleton of the Scottish Ornithologist's Club's (SOC) new headquarters glows with the special warmth of real wood.

Originally, says architect Simpson & Brown associate Jenny Humphreys, green Scottish oak was specified - 'but a much better option emerged when the Forestry Commission got involved'.

Instead of oak the Forestry Commission proposed to use of some of its prized 100 year old Douglas Fir (see box), which could provide the large sections needed. And since, as a sponsor of UK lobby group Wood for Good, the Forestry Commission also proposed to donate the timber to the project, SOC was only too happy to agree. So was the architect. 'The Douglas Fir gives a much warmer feel than oak, ' Humphreys explains.

Large cross-sections increase fire resistance - but no kiln is large enough to dry the Aberlady timbers, which range up to 9m long and 375mm by 250mm in cross section. And it would take several years for the timber to dry naturally. Specialist frame designer and constructor Carpenter Oak and Woodlands production manager Steve Lawrence, however, says this is no real problem, provided the joints and the design details take long term shrinkage into account.

'Frames made from green timber actually get stronger as they slowly dry. The only problem we have had is that some of the purlins warped slightly during the six months they were lying in our yard.'

His company specialises in heavy timber and works almost exclusively with home grown timber and local sawmillers.

For this project it produced the 'log list' for the sawmill (one of the few that could handle 9m long logs), planed the sections, cut the joints and predrilled the peg holes.

The only protective treatment the timbers receive is a coat of raw linseed oil and turpentine, mixed 50:50. 'The only metal connections are at the apex of the roof angle where the two wings meet, ' Lawrence reports.

'And there's only two of them.'

Sustainability is the key word throughout the project. Even the much needed insulation in the building envelope is recycled car windscreen glass, donated by Superglass Insulation.

This will help achieve one of the SOC's key design briefs - a building which is easy and inexpensive to maintain, heat and manage.

According to wood. for good. managing director Charles Trevor: 'this project celebrates Scotland's indigenous materials - particularly timber. It shows that the most traditional of materials can be used to create contemporary, relevant architecture.'

The Douglas Fir

In the late 19th century the Guisachan Estate in Glen Affric came into the possession of recently ennobled former merchant banker Lord Tweedmouth, an archetypical Victorian 'improver'.

One of his last major additions to the estate came in 1905 with the first large scale plantings of the newly fashionable Douglas Fir in Scotland. Some 44ha were planted up, and now, nearly a century later, there are around 145 mature trees in every hectare of what is known as the Plodda Falls stand.

'These are big trees, ' says Forestry Commission Fort Augustus forest manager Malcolm Wield. 'Some of them are close to 60m high. Tweedmouth chose the site very carefully, and the trees have flourished.'

Since taking over the estate in 1937 the Forestry Commission has maintained the stand as a continuous cover amenity planting.

This has to be maintained and regeneration encouraged in a five year cycle - which means felling a limited number of trees to let in the light and encourage the growth of seedlings. Scottish timber merchants anticipate these occasions eagerly, Wield says.

'We always look for some special end uses during thinning operations. Since we started 30 years ago we've supplied masts for many marine heritage projects - including Captain Scott's ship the Discovery in Dundee harbour - and 25m tall electricity transmission poles for Sweden and Ireland.'

From Plodda Falls the logs went to a sawmill in Kirriemuir, Angus, belonging to James Jones, another wood. for good. sponsor. Sales director Ian Pirie says that the trees to be felled for the SOC project were specially selected by both the Forestry Commission's forester and the sawmill manager. 'They were looking for consistent quality, with straight, clean stems, ' he reports.

'Although we have a lot of experience with Douglas Fir, this was exceptionally good.'

Waterston House: the new HQ

The new SOC HQ on the coast east of Edinburgh will be dubbed Waterston House. The name commemorates George Waterston, known as 'the keenest birdwatcher in Scotland', who founded the Scottish Ornithologist's Club (SOC) in 1946.

Appropriately, the site at Aberlady overlooks some of the best bird watching territory in the UK, with more than 250 species recorded.

SOC development manager Bill Gardner says that once a 'dead triangle' of land on the local golf course had been identified, the choice lay between a classic visitor centre and a resource centre aimed mainly at the SOC's 2,000 members. The latter option was chosen, and the initial brief included a large library, a wildlife garden with a range of habitats, and flexible, expandable space for exhibitions and the like.

It was Gardner's responsibility to assemble the sponsorship needed to fund the $1.4M project. Apart from the structural Douglas Fir post and beam frame, the building will feature Scottish oak flooring and will be clad largely in untreated larch. Clay tiles donated by Lafarge Roofing will complete the building envelope, and the new centre is due to open in March next year.

Who's who

Architect: Simpson & Brown

Structural Engineer: Will Rudd Davison

Main contractor: John Dennis & Co

Structural frame design and construction: Carpenter Oak & Woodland

Timber supplier: Forestry Commission Scotland

Sawmill services donor: James Jones & Sons

Oak flooring supplier: Russwood Timber

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