Paint keeps flaking on render

[happyhero]

Hi I live in a mock Tudor style house and the paint on the render does not seem to last very long, ie after painting it lasts 2 years if I am lucky sometimes it flakes in less than a year. A few years ago not having much ready cash I had someone paint it for me who I new was not the most thorough of people but he was cheap and I was around to keep an eye that the job was at least complete and tidy. To be fair I did point out a couple of problem areas for flaking and he did seem to improve these areas, basically they flake much less now. I asked him about what he did and he just said he used a stabiliser. He said there were different stabilisers and that he used one which you put into the paint, as opposed to something you paint on before hand.

Before this I had painted the render with Sandtex exterior masonary paint which looked lovely obviously at the beginning but some of it did flake off less than 2 years later. I then tried using exterior unibond first in a test area to try and seal the walls but to my amazment this did not seem to help at all. I asked about this afterwards and was told doing this was not a good idea as it would seal moisture in the render and thus cause the paint to flake.

Since this I have been Googling the problem and found that my render could be lime render although the dates do not agree. I read that they used lime render in the late 1800's and my house was built in 1933. Also I do not think my house was built or decorated in an unusual way as it is in a group of about 12 houses all built and looking almost identical. My point is, it does not look like someone tried to be different and build it with Lime render in the 1930's unless they decided do that to all 12 of them which I suppose is possible.

Anyway from Google and Forums I read to check this it said you should rub your finger on an exposed bit and see if you end up with a white finger, well I did this and I do so does this mean I have Lime render?

I also looked up what you should do with Lime render and one solution is to use a Lime based paint or whitewash as it appears they call it but this feels like an awkward route to go down, i.e. I'd rather use a well trusted paint, Lime paint seems harder to find and quality is harder to be sure of. Also how long would it last, and where to get it etc.

So my questions are

Does it sound like I have Lime Render?

Is there a long lasting solution I can paint on, so that I can use popular paints, I dont mind paying a little extra for something that works?

Am I better offer using a Lime Paint and if so why?

Any advice or help appreciated.

 

[peaps2]

better off with lime render and lime paint, why? So it won't flake off

any pics?

 

[happyhero]

Here are some images to help does it look like paint flaking off lime render?

 

[peaps2]

If you use the wrong paint on lime it seals moisture and the render degrades. In the 30s it was common to mix lime putty with a little cement to help set the render quicker. This is why we have a common misconception that you can mix cement with lime, 6.1.1 mix. The reason for mixing cement to lime putty was to give it hydraulic qualities, modern lime is hydraulic so no need to add cement, it's counter productive.

You may have a lime putty mixed with cement, I can't be sure without analysing it. Salt become a problem when you add cement but not so much with lime/cement render.

I suspect you have degraded lime putty render due to the paint sealing the wall.

In an ideal world the lime should come off and lime render replaced (NHL5), then use a lime based paint, Lime wash.

The wall can/should be finished of with a lime "skim" to give added protection again the weather using a fine sand and lime, 2.1 mix.