About timber treatment at Caerfagu
The majority of our timber is treated in our own pressure plant using the vacuum pressure process - currently the most permanent method in preserving timber life by reducing the risk of insect
attack, fungal decay (rot) and other biological decay hazards. For impregnation we use Wolmanit® CX8-WB from BASF - one of the world‘s most successful
chrome & arsenic free wood preservatives.
Freshly treated timber has a green finish, which, after few weeks of being exposed to natural elements, fades to a warm light straw colour.
Vacuum Pressure Treatment Process
Before we start the process we make sure that timber’s moisture content is no higher than 28%. The timber is then loaded onto special tram cars similar to railway carriages . The 15 metre train of loaded timber is pushed into the pressure vessel and the door sealed awaiting the process to begin.
- Initial vacuum
First a vacuum is created in treatment plant - it needs to get as high as possible (around 90%) and be held for 10 – 15 mins. This removes the air from the timber cells allowing the liquid to enter when the plant is flooded. - Fill period
It is essential that the vacuum is maintained during this period. If it dropped, it would let some air back in the plant, so the tops of the packs would have more air in them and stop a full cell treatment. Consequently the lower half of the pack would be better treated than the top. - Pressure period
The length of this period depends on the hazard class that timber is to be used for.
Ground contact timber requires hazard class 4 (see table below). All timber at Caerfagu is treated to this standard. - Final vacuum
This is the final cycle period after the pressure period has finished and the fluid has been drained from the treatment plant; ensures that excess fluid is taken out from the packs.
Following the treatment, timber is left outside the plant in dry conditions for a couple of days to let the chemicals physically fix in the intercellular spaces as the water evaporates.
All in all the pressure treatment process takes approx. 3 hrs and, at Caerfagu, we’re able to process around 20m³ of timber a day.
Timber before and after vacuum pressure treatment
Use classes for timber
|
Class |
Type of Use |
End Use |
|
1 & 2 |
Internal - wood is undercover, fully protected from the weather or where high environmental humidity can lead to occasional but not persistent wetting; insect risk |
upper floor joist, timber frames, tile battens |
|
3 |
External - wood not covered and not in contact with the ground-either continually exposed to the weather-or if protected from the weather - subject to frequent wetting |
fence rails, decking boards, garden timbers, external joinery, cladding and sole plates above damp-proof course |
|
4 |
External - wood in contact with the ground or fresh water and permanently exposed to wetting |
fence and gate posts, also all timber in ground contact e.g. decking joists & sleepers |
Caerfagu opening times:
Mon - Fri
8.00am - 1.00pm
1.30pm - 5.00pm
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