Exterior rubbish painting Part 2

[Glug]

So the problem of the brown and yellow stains coming through masonry paint was solved when the exterior painting was done again by the same painter, ie he was given a chance to put it right - in April.
He just painted over the first attempt. I believe water-based paint was used first time round and then oil-based to rectify the staining problem.
However, a small area of the masonry paint is suddenly showing blistering. It's on the prevailing wind side and the past month has been gales and slashing rain. If you press a blister it shows paint underneath, not bare wall.
Before the blistering was evident, the matching area of the interior hall wall showed "salting" and a damp meter test proved positive (the walls are cavity filled).
At the very start of the job the exterior wall was scraped down and some cracks filled in but it was not re-rendered (my decision). I know that the first paint job was not properly prepared because I sent off some samples to the manufacturer. Could this have happened again?
But having got A N Other in, he says that a large part of the exterior wall should be re-rendered (gulp) and then repainted. £1000
Do I have to bite the bullet on this or could there be another solution? Are the blistering and internal damp necessarily related?
Thanks in advance.

 

[TheDec]

Glug.

I am of the opinion that there is a link here between the brown patches which appeared on the water based masonry paint, and as you termed as salting.

It seems apparent that these walls should not have been painted, the appearance of those brown patches indicates a problem with moisture, in other words the ingress of water. The application of an oil based masonry paint will provide you only with a temporary solution.

The salting is called efflorescence and can show itself in many differing ways, I would therefore urge you to take the advice of A N other. Throwing good money away after bad is not really a good idea.

Dec.

 

[Glug]

Thanks Dec. You're talking sense and I wish the builder/project manager had explained what problems might arise by "patch and mend", among other things that went badly wrong with the refurb. But that's another story.
A N Other 2 knocked the area of wall in question and it sounded hollow. He won't re-render just that bit, but says the whole side of a 1930s semi-d has to be done, which will certainly bump up costs.
Trouble is, with my experience with the original builder I don't know whether he is trying it on or whether he's right.
Since it's my late parents' house which I want to sell (now six months late because of many cock-ups) I guess I was trying to do the minimum to make it l right but I suppose a half-decent surveyor would spot the probs.
So in comes A N Other 3 and I guess it's going to have to be the whole wall .. . .
Thanks again

 

[TheDec]

Glug.

You're very welcome, hope everything turns out ok and not to expensive for you.

Dec.