What would YOU use to paint this summerhouse?

[Herbane]

Hi all - recently moved into new house and previous owners painted the garden summerhouse blue, in a Ronseal-type product.

Want to paint over it and everything suggests Cuprinol Shades as the way to go. However, I know that unless the wood is well-weathered the Cuprinol may not adhere properly.

The thought of having to sand the summerhouse down doesn't fill me with delight so I'd prefer to avoid that if possible.

So, do you have any experience of painting over a summerhouse?
Do I need different paint for inside and out?
Should I just prime/undercoat and use an exterior wood paint instead of the 'Shades'?

Any advice greatly appreciated - cheers, H

 

[Space cat]

The Cuprinol products that I know of are designed to soak into the wood. You can use them on bare wood (obviously) or on wood that's been treated with the same kind of product. (The surface remains porous but water repellent.)

Paints and varnishes are different. They contain a resin which polymerizes on contact with oxygen and forms an impervious skin. This is why you get a skin inside a part-used paint tin that's stood unused for some time. It's also why newly dried paint is as soft as clarts. The solvent evaporates quickly but the resin takes much longer to harden fully.

Cuprinol will not soak into wood that's had paint or varnish on it. Moreover, if water does get into the wood by some devious route, it'll be trapped and the wood will rot under the paint. (I learnt this the hard way when I painted a garden seat with a well known brand of wood preservative. It did exactly what it said on the tin and protected the wood for six years - then it started to rot. )

If your existing finish will accept Cuprinol-type preservative, stick with it. (It might not take regular paint anyway.) If not, you'll just have to keep painting it. Keep an eagle eye open for for any signs of rot and attack them early.

Idea: If the inside isn't painted yet, use Cuprinol low odour preservative. The name might have changed but it'll say that it's suitable for interior use and can by painted over when dry. Don't paint it; just top it up occasionally to protect the wood from the inside.

 

[Herbane]

Thanks Space cat.

So you're saying that the Cuprinol Shades may go on top of the existing covering okay? The existing is a blue water repellent wood treatment, similar to Cuprinol.

 

[JohnD]

If it is one of the water-based waxy preservatives, then you can recoat it with another similar product. Clean it first with a stiff nylon brush and a bit of detergent, then hose off and allow to dry fully.

However you will have to wait until the old treatment has eroded and roughened, otherwise the waxy coating will prevent the new one from wetting the surface and adhering. The water-based stain will bead up and try to roll off, just like rain is repelled by the waxy coating.

If you want to apply multiple coats, you either have to do them all the same day, applying each before the previous one has fully hardened; or leave it to weather. Or you can keep brushing the new product to and fro until it starts to soften the old coating, but this takes a long time.

 

[Herbane]

thanks for the reply JohnD - so I have to weather it first before I can repaint? I don't relish the thought of having to go round the summerhouse with a wirebrush....(has been painted inside as well, in the same blue so won't ever get 'weathered' naturally).

Are there alternatives? I really want to cover the blue but it sounds like painting with a Cuprinol product or similar will require a lot of getting the wood back to bare.

How about normal primer and outdoor wood paint?

 

[JohnD]

the stains work by leaving a water-repellent waxy film. So paint won't stick. You can experiment brushing stain to and fro until it softens the old coating and starts to stick (I had to do that on parts of my shiplap cladding), but I think you will find it a very long and tedious job.

It might be possible to soften it by wiping with meths, white spirit or something, I don't know.

Or you could write to the manufacturer for advice. Best to use the same brand for your new treatment as was used before in that case.

 

[Herbane]

Hmm,

The manufacturer said pretty much what's been said on here: needs to be weathered or taken down to bare wood first.

So I can't prime and then paint it with regular paint, doesn't sound like I can apply a Cuprinol-type product either....

Is my only alternative to take down the old summerhouse and get a new one?