Problem with paint on garden wall........

Dinarius

We had a garden wall painted about 2 years ago.

Recently, whenever it rains heavily, the paint bubbles in many places.

Why does this happen? Is it the wrong kind of paint?

How can we cure it?

I should add that it's a garden in an apartment development, so the painter was hired collectively.

Thanks.

D.

Wertz

Sounds to me like interior matt emulsion was used...but it could also be down to the substrate the paint is sitting on top of....a lot of surfaces need to "breathe", some more than others, and bubbling like you describe is the wall trying to breathe through a layer of paint. There is also the possibility that the wall was not 100% cured when it was painted (not an unusual occurence these days unfortunately)

Only way to solve this is find out what the substrate is (probably rendered concrete) and use a power washer to blast off as much of the old coating as you can, then uses a propreitary exterior masonry emulsion like WeatherShield.

Oh this may also come back to the fact that the raw rendering may not have been stabilized. If that's the case then the *first* and only the first, coat of whatever you decide to put on it, should have a product called EB added to it. It's made by Owatrol and adds a property to the paint that makes it adhere to an unstable surface.

Dinarius

Wertz,

Given the cowboy job that this apartment block is, it wouldn't surprise me if the the render is unstable.

Will check up on the paint used though.

Many thanks.

D.

mad m

If its unstable then only thing to do is stablise it with stablising solution,you can get this in a water based paint or oil based,I myself prefer the oil based solution.Then next day use a good masonary paint.

But if it was painted two years ago and only now the bubbles started to appear then I'd say you did ok.I would have to paint my walls atleast one to two years depending on conditions before signs of flaking or bubbling appear.It is outside walls after all and open to the elements.

But if it was done recently then Wertz is right,normal interior emulsion was used,which does not hold up much to outside weather conditions.

rooferPete

Hi,

Keep the thinking caps on lads, your getting close but "No Cigar"

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Wertz

Also possible that the wall isn't properly damp coursed too

rooferPete

Getting closer

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mad m

Effloresce? Go on pete you are dying to spill beans.Maybe the garden is above the damp proof coarsing? Thus leading to rising dampness!!

rooferPete

Hi mad m,

Not what I have in mind but I wouldn't rule it out as a side effect

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Victor

Ah, stop teasing Pete.

I'm "guessing" that there is a dpc missing at either the top (under capping) or bottom (150mm above ground level) of the wall.

Water is coming in, building up behind the paint and then washing the paint off.

rooferPete

Hi Victor,

Very nice drawings, my guess is there is no plinth on the garden walls so even with a DPC the water will still climb up through the plaster pushing the paint off.

Take the very same wall and put a plinth on the other side and the water will not climb higher than the plinth leaving the paint bonded to the plaster surface but only on the side with the plinth.

I have seen garden walls plastered without plinths and the water climbing up as high as three feet through the plaster finish.

The same walls painted a year later and the paint bubbles off the lower three feet.

Capillary attraction.

.

Dinarius

Peter,

Nothing about the build quality of this apartment block would surprise me!

Where exactly would a plinth be? i.e. how near the ground level?

If that is indeed the problem, is it easy to remedy?

Thanks.

D

Victor

Dinarius wrote:

Where exactly would a plinth be? i.e. how near the ground level?

The plinth is the bit of plaster below the projection at DPC level. Typicly 150-300mm above finish ground level. The minimum should be 150mm because of splashing.

Dinarius

Victor,

Thanks for that.

This wall is a smooth block wall with supporting pilasters attached.

I can't see any plinth.

Next time it rains and bubbles up I will photograph it and post a link to the image.

Thanks again.

D.

Dinarius

Today's weather presents the perfect opportunity to illustrate the problem!

Images of our wall are here.... http://homepage.eircom.net/~ThePlayer/IMGP1633-1.jpg

and here.... http://homepage.eircom.net/~ThePlayer/IMGP1635-1.jpg

Note all over bubbling. It simply gets bigger in spots. About a day after the rain stops, the paint completely flattens again, and you wouldn't know there was a problem except for the cracked paint under the cap stone.

Is this the paint or the wall?

Thanks.

D.

Wertz

Is it the paint or the wall

Bit of both, but problem is most likely based on the wall's construction, as the guys have said....until you sort out the damp course or whatever the root problem is, no paint job is going to last pissing time...

Victor

Its not a great detail, the cutting on the capping is poor and I'm gussing there is no DPC under the capping.

Investigate. Remove capping (full length of wall) and clean. Add DPC, make sure it is well lapped at the slope. Replace capping. **Minimise mortar joints in capping, especially at bottom of slope**.

Remove paint with wire brush. Loosely cover top of wall with sheet of plastic. Leave wall dry out. Repaint.