1- Larger diameter round timbers cannot usually be adequately dried before use, and shrinkage is inevitable. Cracking can be controlled by cutting slots or saw kerfs along the length of the member, and end splitting can be resisted by nailplates driven into the end grain or strapping around the member circumference. |
2- As far as possible, structural round timbers should be located such that their ends are not directly exposed to rain, since end grain provides easy access for water. Simple caps or flashings can be used to protect the ends of exposed members, extending their service life. | | Examples of cappings at exposed beam end (left) and exposed head of column (right) |
3- To achieve maximum life a round timber structure should be isolated from the ground. This can be achieved by steel shoes, plates, posts or bars, or with concrete base. | | Anchorage detail ensuring column’s end is isolated from the ground |
4- A major cause of decay is the formation of water pockets at joints between structural members or at supports. Shaping, caulking, grooving and drilling can encourage drainage away from joints. Whenever possible and air space should be provided to prevent capillarity action into the end-grain. | | Shaping of exposed continuity joint to avoid water traps |
5- The design of a structure for agricultural activities, eg animal accommodation, should specifically address robustness aspects, eg risk of animal impact on structural members. |
6- Large eaves overhangs can minimize the flow of rainwater over the wall elements, reducing the risk of decay. |
7- The choice of the correct timber species is essential to ensure good performance and to minimize maintenance in service. Those which fulfil the basic requirements may need to be treated to improve their natural durability see Structural engineering design with round timber. |
8- Preservative treatments are available that enhance timber natural durability. Structural round timbers feature a proportion of sapwood which is not durable. The use of preservative treatments should therefore be examined, see "Round timber in construction: Notes for structural design". |
