Q. Why treat wood?
A. Wood is one of the world's few renewable resources. Softwood from sustainable plantations relieves pressure on the world's limited tropical hardwood resource and avoids the use of polluting non-renewable products like steel, concrete and plastics.
Q. Why do some species of timber last longer than others?
A. When a tree grows, it conducts sap up the outside of the tree, and the centre of the tree forms heartwood. The tree deposits waste products in the heartwood. Some of these are natural preservatives. The heartwood develops “natural durability”. This varies from species to species and can be referenced in a timbers “Natural Durability Classification”.
See EN 350 part 2 for the full specification on “Natural Durability Classification”.
Q. If wood is classified as “Naturally Durable” why treat it?
A. The “Natural Durability” classification only applies to the “heartwood”. All commercially supplied softwoods include “sapwood” which is not naturally durable. By applying wood preservative we are converting sapwood from “non-durable” classification to “durable classification” and extending its useful life by 3 to 5 times.
Q. How do I know what treatment to ask for?
A. First identify what the timber will be used for. There are 5 “Use Classes” which define the conditions the wood will be exposed to during its use. EN 335 defines the Use Classes in detail.
By specifying the appropriate “Use Class”, your timber supplier will be able to offer the appropriate product for the job.
Contact Impra Wood Protection if you need any help.
Q. How do I know what Use Class the wood is suitable for?
A. Ask your timber supplier for a “Certificate of Treatment” which defines the specification the wood was treated to. This is an assurance that the wood was properly treated for the Use Class.
Q. How can I tell if the wood is treated properly?
Some preservative products are coloured so easily recognisable on the wood surface, however, superficial treatment may not be good enough. For Use Class 3 and Use Class 4 applications preservative penetration into the wood is specified.
For a thorough check, a boring or a cross cut sample may be necessary to check how deeply the preservative has penetrated.
Clear preservatives may be identified with a reagent.
Lab analysis can determine if preservative type, penetration into the wood and application rates have been complied with.
Contact Impra Wood Protection if you need any help.
