Painting tongue and groove panelling in a bathroom

[Penners]

Biff

The concept of protecting wood with paint is largely a myth encouraged by the paint industry.

Don't you think that the type of wood that we generally tend to use nowadays is the principal culprit? If all woodwork that is to live outdoors was oak, then certainly there would be little need for paint as a protective medium. However, relatively few people can afford oak woodwork - or at least, they think they can't afford it. If they were to compare the relative costs of a - say - a softwood window frame (including painting costs, replacement costs, etc), with an oak ditto, then I dare say there wouldn't be much difference in the long term.

Trouble is, we don't live in a long-term world.

 

[biffvernon]

Yes, you're right, Penners. Some of the 'whitewood' commonly available is not at all durable. On the other hand, I reckon that exterior joinery made of Scott's Pine, 'redwood', which is not classed as a durable wood, would last longer if it were not painted than if it were painted with a modern waterproof paint, so long as the detailing allows it to shed water and dry out rather than sit in a puddle.
I've got some big garage doors that are probably more than 50 years old and had lost most of their paint twenty years ago when I moved in. I've not repainted them. The wood is still sound except for two planks that get dripped on from a leaky gutter.
My contention is that, given good architectural detailing, exterior joinery is better left unpainted than painted with a waterproof paint, no matter what the timber.

 

[Penners]

So would you then leave a Baltic/Scandinavian Redwood window completely naked, or perhaps use linseed oil or similar?

 

[biffvernon]

It should be painted with a linseed oil based paint. The oil soaks into the timber forming a very intimate bond. It will never peel off but it will shed the rain and allow water vapour to pass out of the wood. The wood will stay dry and not rot.

Painting it with an alkyd resin paint is worse than not painting it at all because the paint forms a waterproof surface film, which is fine until it cracks, which it inevitably will since wood and paint move differently. The water will get in but not be able to dry out again. The paint will then flake off, but perhaps not before decay has set it.

In Scandinavia redwood is often used as weatherboarding and left unpainted.

 

[worms]

I tend to agree with Biff here, having stripped a hardwood front door a year ago and never finished the job, it remained drier inside and out last winter than it did in previous years when we used to get condensation on the inside of it in cold wet weather. The wood dries out pretty quickly after the rain stops.