Over the last couple of years I've built two sheds/workshop. Having taken advice from here I coated the shiplap (which was vac treated) with up to 6 coats of tung oil.. On the first workshop all went well the first year, but having recoated it last summer (and treating the second shed likewise after build), both have suffered badly over the winter. Mould has covered most of the boards (the SW facing ones which take the brunt of the weather fared worse) and in the worst affected areas the wood expanded so much it started to 'round' (gaps were left between the shiplap on construction to allow for expansion), and some tiny 'cracks' have appeared. The wood is 'sound' though.. So if we ever get summer back, I need to get a protective coating on them..obviously I need to sand the wood quite thoroughly, but given that I don't want to use the oil again, some questions.. What do I need to do to the shiplap so that the oil that has been applied previously doesn't affect the new coating?...only one area is very slightly 'sticky'. Would a clean with white spirit suffice? The reason for using oil in the first place was to try and keep the wood in it's natural colour, so is there a durable clear treatment that I could now use? If a coloured treatment is better, what would be the best to use which only gives the wood a light shade of brown? cheers.