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How traditional green-oak construction can be used in a

commercial building.

Green oak construction is a specialist skill that is rapidly disappearing, and when it is used, it is often in restorations, or rural domestic buildings. Malcolm’s Golf Shop and Tea Rooms is an inspiring example of how this traditional method can work in a commercial context, providing a modern space out of this beautiful material.

Introduction

Truro

Exeter

Salcombe

Malcolm’s Golf Shop

Key dates Planning approval : November 2005Trees felled : 2007 Build : 2007 – 2008

Exterior - Photo © Tom Vanstone

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ContextThorn Park Golf Centre at Salcombe Regis is a 30 acre, 9 hole, golf course set in a picturesque, historic village which dates back to the Doomsday Book in South Devon. The historical nature of the surrounding area was an important factor in the design and development. The materials would both be aesthetic and relevant to their surroundings. Malcolm Burrow wanted the building to be in keeping with its environment, as well as being functional and fit for purpose. The 30 acre site has a variety of trees, and as several oaks had to be felled in the spring of 2007, Malcolm

thought that using these as the main building material would be ideal not only because it would provide him with the type of building he envisaged, but that the impact on the environment would be also be reduced by reducing haulage and transport.Malcolm chose to use local Portland stone from Dorset, reclaimed tiles and softwood cladding, as he felt that not only would they enhance the build aesthetically, they would also fit in with his desire for this to be a low impact build.

Oak - Photo © Servane Guihaire - Constructys Bretagne

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Building overviewIn order to comply with building regulations, the foundations of the two storey timber framed structure are reinforced strip, or trench foundations. On top of the foundations, the plinth was constructed of cavity block on which the oak frame would rest. In contrast to other building methods, the wall fabric of the building did not use a cavity system. The frame is counter battened with a membrane and then Cedar wood was used for the external cladding.The Portland stone on the veranda and the reclaimed tiles on the roof,

blended well with the oak and wood ; the overall effect was one of harmony within the structure and with the surrounding environment.

Technical focus : Building the oak frameThe Green Oak for the Golf Shop Frame was milled on site using a mobile band saw, which enabled Tom and Ben to maximise the amount of wood used from the felled trees. Also the time, energy and potential risks were reduced due to the ability to produce the construction materials onsite.

Using the freshly felled timber

Before cladding - Photo © Tom Vanstone

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The architects do not have the understanding and appreciation of the strengths and benefits of Green Oak, and view the shrinkage that occurs as the oak dries as an issue that they would rather not have to

Frame - Photo © Tom Vanstone

meant that the drying movement or shrinkage of the timber would now take place after construction and during occupation. This means that the movement due to change in the frames moisture content, cannot create any weaknesses in the joints and that the fabric of the building retains structural integrity. Another benefit of oak seasoning in situ is that the surface marks, or fissures that might occur, are acceptable compared to other ‘clean’ pre-seasoned wood. This is why an understanding of how the wood moves as it dries, and how the grain effects shrinkage, makes working with oak a craft that requires specific skills and experience.The frame for the shop and café was a double isled structure which would allow room for a veranda on one side and a large counter area on the other. This would leave a large open plan central area for the shop down stairs. Upstairs, open slingbrace frames were used to create an open office space.

Green Oak as a viable building materialGreen Oak can simply be defined as oak that has been recently felled. «Green oak is not used enough in new building projects», states Tom Vanstone, of Devon Oak. He believes much of the problem lies in the lack of knowledge with the architects who are usually the first point of contact for clients wishing to commission a new build.

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deal with.This lack of knowledge and understanding of how green oak works when being used is not there, and thus, working with it, is a skill which is rapidly disappearing, whereas, historically, it was the main technique for building with wood. During the Medieval period it was common place, and within England,

many examples of the work are still around today.If oak is dried out (seasoned) it becomes incredibly hard and it becomes very difficult to work with, even with today’s modern power tools. As the oak dries out it has a tendency to crack or split length ways, which results in the loss of often substantial amounts of useable timber. Compared to soft wood, oak dries very slowly.

Outside frame - Photo © Tom Vanstone

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A section of frame 200 mm thick will take 6-8 years of air drying to lose the excess moisture, and the use of kilns would not achieve a significant reduction in the time. This is a practical problem as most oak framed buildings are bespoke, so keeping seasoned pieces in stock does not work. If a project could wait the 6-8 years for the pieces to season; the removal of the excess moisture causes the timber to shrink and would affect the build as oak has a high drying shrinkage coefficient. These are the reasons that Tom and Ben of Devon Oak work in Green Oak and not seasoned oak.

The Benefits and strength of Green OakThe benefits of Green Oak compared to Glulam and Douglas fir, which are viewed as having comparable material unit costs, are that oak is naturally durable, does not have to be treated and has very good weathering properties. The wood has an attractive finish and so can be left exposed reducing the need for the application of other finishes. Oak also has very good fire retardation aspects, with its structural integrity exceeding steel I-beams of similar size. More details

Inside frame - Photo © Tom Vanstone

StakeholdersClient : Malcolm BurrowArchitects : ARA ArchitectsPrime Contractor : Devon Oak – Tom Vanstone and Ben Gillespe

Costs The client, Malcolm did a lot of the work himself, bringing in local contacts to help with the brickwork. He also saved a lot of money by hoarding reclaimed materials such as the roof tiles and bar top and by using trees felled from his site.

As the Golf Shop was not a domestic building, it isn’t necessarily heated for much of the time so energy performance figures were not done.

Performancecan be found in BS 5268-4 and BS EN 1995-1-2.When comparing oak to steel, bending tests undertaken by TRADA and the Forestry Commission found that although the variation of bending strength of green oak is 15% and that steel is over three times as strong as oak, the steel weighed 10 times more.

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Back of the building - Photo © Tom Vanstone

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