These jobs are always a nightmare to try and get right !
Osmo specify on their technical data sheet that minimum of two coats of Uv Protection Clear Satin oil should be placed on new timber cladding. It also specifies you should coat the back of the cladding before installing.
The coating of the back of cladding I agree with but if I ever get asked to complete an Osmo oil job like this, we always specify to the client that they need to put 4 coats on if it’s in a coastal location like this particular house.
The reason we specify this is that the first coat brushed in really just penetrates into the wood fibres and leaves a tiny covering on the surface. Then when you apply a second coat this penetrates the first coat and then sits more on the surface.
Over time with the the wind, rain and sea salt in the atmosphere, these components basically wear down that second layer over a season.
What then starts to happen is you lose your factor 12 sun uv protection in the oil and the sun starts to bleach the wood. Not only that the water and weather start to react with the wood and it starts to get grey patina on the surface / ie the greying process starts.
This is an absolute nightmare to correct if it goes to far. Osmo recommend the ‘ Osmo Reviver Gel ‘ but this can only do so much and you have to wash down wood , scrub it in and leave 20 mins then wash down wood again and wait to dry.
I’ve tried it on so many jobs but doesn’t always work.
Firstly you have to mark out where the grey patina has occurred then treat with Osmo Reviver Gel. Next you leave to dry for 20 mins wash off then recoat the plans that have been treated.
You then put a final two top coats over the whole cladding again so that you know it has the sufficient coatings to get through another 2 seasons.
My suggestions for cladding would be always put 4 coats on or at least 3 then after first season reapply another 2 coats then every other year apply 1 coat for first five years.
This will prevent any greying or bleaching of the cladding no matter where the location is of the property.
We completed this job to the exact instructions from Osmo on this multi million pound property and just managed to catch the wood in time to be able to renovate it properly.
I expect another year of weather conditions and this wood would have gone to far to be able to renovate.
My instructions to all homeowners installing red cedar that they want to keep the natural look of the wood is ……
PUT 3-4 COATS ON AT INSTALLATION STAGE
ITS A MUST !
Owner @ Stuart Elliott Decorators Ltd