leenowell wrote:

I have some old rendered walls which I would not

now(?)

like to paint the same
colour as the house. About 6 months ago I painted them with some left
over house paint. It seemed to take forever to dry and the following day
it rained and the paint run off the wall.

Is it a silicone render, such as K-Rend?

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On 01/04/2025 17:27, leenowell wrote:

Sorry, yes that should have read now 😀

No it is regular sand a cement render. It was done at the same time
using the same materials as the house. We just didn't get around to
painting it for years.  The paint is a Dulux Trade exterior masonry
paint . Was wondering if the render needs treating / cleaning with
something or maybe watered down for first coat or something?

I have a problem with Sandtex masonry paint flaking off after a few
months. It dries perfectly well and doesn't wash off. but it does fall
off in large flakes (maybe a few inches across). Some parts of the wall
are affected worse than others. It's sand-and-cement render on brick,
done about 30 years ago, long before we bought the house.

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On 01/04/2025 16:27, leenowell wrote:

Hi all

I have some old rendered walls which I would not like to paint the same colour as the house. About 6 months ago I painted them with some left
over house paint. It seemed to take forever to dry and the following day
it rained and the paint run off the wall. Some patches dried but having
now pressure washed them to have another go some of the paint came off. Anyone any ideas what is causing this and what the solution is?

Many thanks in advance

Lee.

You say left over (masonary?) paint but how was it stored? Could it have frozen/frosted over a previous winter? How well was it stirred before use?

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It has been stored in the garage so not likely to have frozen. We have a
fridge freezer and the boiler/ tanks in there too so if there was a
freeze that heavy then it would have impacted at least the fridge
freezer. Stirring issue could be the case as it is in a big container
and some paint decanted into a smaller pot.

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