I originally posted this in the damp proofing section but thought I'd try my luck here too.

I had a retaining wall built in my garden last year. It is concrete block that was then rendered.

I painted it with ordinary masonry paint in the Summer and over Winter about 1/4 of the paint blistered and loosened.
I have removed all of the loose paint with a wire brush, some of the paint had what looked like fluffy white mould behind it attached to the wall, (effluorescence?).

My question relates to how I should remedy the problem. Obviously masonry paint on its own won't do the job so I have the option of treating the wall as if it were garden furniture, wire brushing and repainting each Spring, about a 3 hour job, or some kind of alternative.

Someone I know suggested Unibonding the wall before repainting with masonry paint but this can't be good for the wall can it? Sealing in damp, surely it's better to let the damp pass through to maintain the integrity of the wall.

Is there some sort of stabiliser I could add to masonry paint, would it make any difference?

I have done some research and found a paint product that doesn't create a seal and bonds with the cement in the render, it's called Durbocem and sounds like it'd do the job but it doesn't come cheap, £90.00 for 10 litres, which is the amount I would need.
Does anyone have any other, more costs effective ideas, that would solve the problem.
I don't mean to sound like a skinflint but if we were to have a particularly hard Winter, not unheard of recently, and the render blew and had to be removed and re-rendered then I'd be shelling out for another tin of Durbocem.

Any suggestions would be greatly appreciated.
Thanks,
Sean

I nearly answered it in the damp proof section too, but as the question is 'does anyone have any more COST EFFECTIVE solutions' my answer would have been 'NO'...
however,
seeing as your here....

my solution, albeit not exactly cost effective, would have been to either...

a) dig back all the soil from the back of the wall, and install a cavity drain membrane... running a french drain along the bottom containing a draininage pipe to a soakaway away from the wall...
what that would do is hold the soil away from the wall and allow the water to drain down into the french drain and then into the soakaway therefore stopping it soaking into the wall, bringing salts with it to the face and ruining the paintwork...

or b)

hacking off all the render...
installing a similar membrane to the front, followed by insulation, followed by a thincoat through colour render system....
what this would do is allow the water to pass through the masonary where it would come up against the back of the membrane and drain down without passing through the render...
the insulation over the membrane but under the render would stop the water freezing, expanding and blowing the render coat in winter...

other than that I have absolutely no idea other than maybe building another face brick or rendered block wall in front of the existing retaining wall leaving a cavity....

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http://www.peterborough-plasterer.co.uk/

you could try digging the earth back then rendering the back of the wall aswell with a waterproof render then seal it with a sbr coat, then replace the earth this would stop the water getting to the concrete blocks in the first place and passing through to the renderd face thats on show.

you reckon? i dont....

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http://www.peterborough-plasterer.co.uk/

once you have made it water TIGHT on one side how can the water pass through to the other side, the side that is on show.
and if you dnt agree theres no need to be a d*ck about it is there just list your pros and cons about the listed idea as apposed to makeing the person with the idea look stupid when they are not, after all even YOU said you dnt really have an idea and i was just putting anouther idea out there.

Chris has got it cock on, the only way to do it is by using a membraine. Rendering it both sides WILL NOT sort out the damp problem, no mater how much waterproofer you use.

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Plasterer in Coventry