[ryetek]

Hello,

We have a wooden greenhouse that's starting to show it's age. I'm thinking of painting it with some kind of clear wood preservative but I need something that's plant friendly. Please note also that the wood is pressure treated and tanalised just in case that makes a difference.

Does anyone have any suggestions as to what would be the best action to take / product to use?

Thanks in advance for any replies.

[rowbow]

If it's cedar don't paint it will flake off, use raw linseed oil (not boiled) the oil will soak in and harden the wood. 

[hasbeans]

Water based paints and protectors are of little use in my experience and will require frequent reapplication.
There are some posh paints like Osmo which have wax in them and will end up costing more than the shed is worth if it's good ol' pine like most of the timber used today in uk.  I haven't tried Sikkens but it has a good rep', again probably too expensive.
I used sadolin classic on my shed frame and will use it on the greenhouse I'm building this year - it is oil based though so might not meet your criteria.  I used it because I got a load cheap on ebay and wanted something  more resiliant than water based paints.
Don't forget that tanalised is not waterproof so you might want to let the shed dry out a bit in spring before painting, you don't want to lock water in!.  Also check the roof covering and corners, the best paint in the world is useless if the water gets behind/under it.
Good luck!  I suspect that unless money is no object or you don't mind painting the shed every year that you will end up with some compromise on green credentials of products.

[ryetek]

Thank you for the replies. I will have a Google on the products suggested above and will have to come to some sort of decision.

If it's cedar don't paint it will flake off, use raw linseed oil (not boiled) the oil will soak in and harden the wood. 

rowbow: Do you know if the linseed oil will work okay with pine?

[rowbow]

Yes, it works on all wood, when we used wooden mallets a new one would have the shaft taken out and the hole filled with linseed oil (the other end plugged with putty)it would take a few days, you keep topping up until the oil shows on the face of the mallet, the mallet is heavier and harder when cured, before the Christmas break we would oil all of the wooden tool handles/shafts,so yes it does work on all woods.
 

[ryetek]

That's great. Thank you rowbow. I'll wait until the wood dries out this spring and then I'll paint it with linseed oil.