Never assume that any timber product that has a treatment colour pigment has been treated appropriately, the type of preservative treatment and amount of preservative loading determines if the timber has been treated appropriately, based on the final desired end use.Pressure treated timber is undertaken in a pressurised tank (chamber or vessel) and pressures can be adjusted accordingly depending on the species and the desired end use; timber or wood products that are likely to be at a higher risk to wood destroying organisms- based on the use classes e.g wood in direct ground contact like timber posts UC4 will be treated under high pressures. Timber or wood products that have a lower risk of wood destroying organisms e.g timbers or wood products used internally undercover UC1 will occasionally be done under low-pressure preservative treatment. Pressure treated wood has to achieve specific penetration and retention levels based on the intended end use of the product. Always check or request that your timber is treated to BS8417 and specify the desired service life of your timber e.g 15, 30, 60 years. more on the use classes UC and service life on treated timber is available on( How long will my wood last without rot or decay?)
You have the right to request a treatment certificate for you to check and ensure your timber has been treated to the appropriate use class. High-pressure treatment brands you would find on the market include Wolmanit® CX8-WB, Wolmanit ProAdd WR, (Tanalised) Tanalith C, Tanatone, Tanasote, Shades, Tanalith Creol, Tanalith BARamine, MicroPro Micronised Copper, Celcure AC500, Tanalith Extra, Impra lit and Low-pressure treatments include Vacsol Resistol, Protim, Wolsit KD.
All treated timber needs to be end sealed when you trim or notch out sections with products like ensele end preserver etc. it is recommended that if you cut along the length you retreat the cut section.
Posts for ground contact need to be incised to ensure penetration of preservative for UC4.
Timber treatment is for protection against wood destroying fungi and not wood discolouration mould. Timber can be pressure treated and still be affected by wood discolouration fungi which do not affect the strength performance of the timber. To avoid mould growth store timber in a dry aerated environment free from contamination. Once timber has had mould infection it can be very difficult to get rid of it. If you are ordering large volumes of timber you could request an Anti-mould additive to be added to your treatment.
Some of The leading timber treatment suppliers are BASF Wolman Gmbh, Koopers Osmose, Lonza Wood Protection (Arch chemicals)and Impra these tend to ensure that their treaters provide wood preservative conforms to the efficacy requirements of EN 599-1 and BS 8417. They work closely with organisations like Wood Protection Association (WPA ) a technical and advisory body on wood preservation.
This ensures that timber is treated in accordance with the penetration and retention guidance given in EN 351-1, to provide the desired service life in the selected Use Class defined in EN 335-1
Always reuse treated timber as opposed to trying to dispose of it, as some of it is considered hazardous waste.