Increasing use of timber in farm buildings

By Hugh Scanlon

26 April 2003: Coford, the timber research council, is to investigate the possibility of getting a new design of timber cattle housing erected on one of the Teagasc research farms so farmers can see and evaluate its merits in a working environment.

This is the main conclusion to emerge from a workshop, organised by Coford, to consider design options for agricultural buildings which will maximise the use of Irish timber.

Study on timber design

The catalyst for this meeting was a Forest Service funded study undertaken by David Kirk at the Timber Development Centre of the Dublin Institute of Technology (DIT).

The study examined the use of Irish timber in farm buildings and the scope for increasing this usage.

When this study was initiated, in 1996, farmers were investing around e250 million a year in farm buildings.

Only around 1% of these buildings included any significant amount of timber in their construction.

This is in stark contrast to many of our European colleagues, such as Germany and Scandinavia, where 90% or more of farm buildings are constructed from timber.

Kirk freely admits that we have a long way to go before we could compare with the situation in Scandinavia and southern Germany, where every farmer also owns a forest. Part of the arrangement between farmers and sawmills there is that a portion of the timber that farmers bring for sale will be cut to an agreed specification and returned to them for use in the construction of farm buildings.

However, he believes that there is scope for a very significant increase in the volumes of home-grown timber that is used in Irish farm buildings.

Key objectives

The DIT study had a number of key, basic objectives:

& To fully develop the design criteria for timber cattle and sheep buildings.

The end product is the detailed design for a timber slatted cattle shed that Kirk believes can give comparable performance and use life to a conventional concrete and steel design.

It is interesting to note that the Farm Development Service of the Department of Agriculture has been an integral part of this project throughout, and it has revised its specification S101, on the structural framework of agricultural buildings, so that it now includes sections on timber-framed buildings.

Effectively, this means that timber-framed buildings that comply with the new specification will now be eligible for grant aid.

& All buildings must be capable of being constructed from C16 strength class Irish Sitka spruce vacuum/pressure treated with an approved preservative.

The design specifies simple plywood gussets nailed into place using specified nail patterns.

At the time of testing, Oriented Strand Board (OSB) was not judged to be suitable for the very aggressive environment that exists on farms, but with improved gluing techniques this may change and the spec could be altered accordingly.

& Issues relating to the durability, maintenance and acceptability of timber by farmers had to be addressed.

For example, the timber uprights are kept 100mm (4 inches) above the ground by being bolted onto galvanised steel plates that are fixed in concrete.

Similarly, the side cladding is protected internally by steel barriers to prevent damage by heavy animals.

As can be seen from the drawings below, the design mirrors conventional designs to ensure that it is acceptible to farmers.

Conventional slatted tanks are constructed below this building, but these are not shown on the drawings.

& The cost must be competitive with current designs.

A desktop study comparing the cost of building a timber slatted cattle shed with a conventional concrete and steel slatted shed costing e20,000, indicates a cost saving, in favour of timber, of around 5%.

David Kirk makes the point that timber is lighter and easier to work with - but Chis Robson, senior architect with the Department of Agriculture, points out that contractors will often build in an additional margin when carrying out works with which they are unfamiliar. For this reason, among others, those at the workshop felt that it would be important for a contractor to specialise in this type of building, with all the benefits that flow from this.

Conclusions

At a time when the volume of timber coming out of our forests is increasing rapidly, it makes sense to be seeking out new uses for Irish timber on the home market.

However, the farm building market is known to be quite competitive, and designs incorporating increased use of timber will only be adopted by farmers if they can be shown to compete with existing designs in terms of performance, working life, appearance and price.

The work carried out by David Kirk, at DIT suggests that Irish timber can make the cut (if you`ll pardon the pun). And the fact that the Department is prepared to grant aid these buildings should give farmers the confidence to give them serious consideration.

It is now crucial for farmers to be able to see one of these buildings in operation.

This can be achieved either by having one built on a Teagasc farm or by having the design adopted and pushed commercially by a building contractor or sawmill.

From an environmental viewpoint, timber should score if the embedded energy efficiency of different building systems begins to be taken seriously.

By this I mean that the timber used is a renewable resource, grown in sustainably managed forests which help to reduce our greenhouse gas emissions.

This figure compares very favourably with the significant amount of energy, derived from fossil fuels, required in the manufacture of concrete and steel.