Hello
I’ve got an external breezeblock wall that I’m thinking of rendering. But the question is - if I didn’t render it, could I paint a crepi finish on the blocks instead. Would that look any good or does it have to be rendered first?
Thanks.
I have had a lot of this done recently and to be honest you do really need to render it first with crépi or the blocks will show through the painted finish. My gate pillars are block construction but with two good coats of crépi and then three coats of the recommended paint, they are looking the bee’s knees and not one single indication they are only blocks. Doing things half hearted or cheaply means re-doing again in a couple of years whereas all I have to do is a coat of new paint which currently should last years! A neighbour has just pained a block wall, it looks dreadful!
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Thanks very much for that @Shiba - that’s just what I wanted to know - what it looked like without rendering.
And just out of interest, what paint did you use?
They do special exterieur paint for Crépi if you go to the tubs of crépi in L.Merlin for example. I can’t give you the name as my son finished up the big tub of crépi on his house and also the tub of white paint. You need to be patient with crépi as a lot will fall on the ground when you are levelling it on but its not expensive so buy plenty and it does keep for some time. Oh and wash it down if it falls on pavers or anything other than the dirt as soon as you can, I kept a bowl and sponge handy.
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Thanks for the useful info @Shiba. In fact, yesterday we went to Brico Cash at Thouars and during our lookround we did see the crepi - that’s what made us ask the question. We were surprised at how cheap it was and they seemed to have some for old buildings and some for new builds.
Crepi, paint with sand in it?
As I understand it, it’s like Sandtex you buy in the UK.
You made me go and Google “crépi” - SF is always a learning experience!
I guess it depends on how well the block wall was built and the state of the joints. If it’s not flat to start with or with deep, unfinished joints I think rendering first would give the best finish. If done well with chaux render it wouldn’t even need painting or crepi.
Why do so many block walls show the joints when its been raining in France? We have a few bad walls near me in the UK but not as many as I see in France.
@Mark - what’s involved with chaux render i.e. what material is used and how is it applied - with a trowel or any other way. It would be a new technique for me to learn, which is good.
For a block wall, I would first give it a coat of PVA. I’ve always used chaux naturel (NHL 3.5, St Astier) with a mix of 2 or 2.5 sable riviere to 1 chaux (as long as its consistent it doesn’tmatter, some people use 3:1), mixed using a cement mixer to a consistency of melting ice-cream . You can apply with a trowel, but a float is better, but it takes a bit of practice. Youcan get away with one coat, but 2 are better, 1st one a thin 5mm that can be scratched when drying to give a good base for the 2nd. This can be smoothed with a taloche, left as a trowelled finish, sponged or (my preference) a scratched finish using the thing that I can’t remember what is called, something like a “gratton/grattoir”
I much prefer SBR as do most these days, has some silly names like Sika adherence etc but its SBR, SBR is more stable for exterior use.
From my construction days in the UK I only recall solid blocks whereas in France they are mainly hollow. This means there are permanent internal cavities within a block wall and the only ‘solid’ parts are the bed and perp joints. A change in moisture within the air when raining and actual rain on the block surface whether rendered or not will not necessarily penetrate the walls surface but the hollow parts will dry the surface quicker than the solid parts hence the beds and perps dry out slower and the joints remain visible for longer.
I have not researched my explanation but to me it seems a logical explanation.
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Yes, would make some sense. I know from testing mortar joints on buildings that the joints made in cement do take a lot longer to dry, unlike lime mortar.
True. My garagiste just ran white emulsion over the blocks that are his workshops. Slighly more light, perhaps, but they look worse than the raw blocks around my back yard.
Here’s a thing. I read that spraying block walls with milk/yoghurt encourages lichen and plants to take up residence. I notice that my concrete block walls are pretty much bare whereas the stone walls next to are a picture of moss, lichen and plants. Something in the material, I guess, keeps them naked.
that brings back a smelly memory…
a friend smothered a large pottery garden thingy… with cow dung… in order to make “stuff” grow on it and thus make it blend into the general natural appearance of his extensive garden…
Live yog and unpasteurised milk work best
For some reason Benny Hill’s song “Ernie, the Fastest Milkman in the West” just popped into my head:
She said she’d like to bathe in milk, he said, "All right, sweetheart, "
And when he’d finished work one night he loaded up his cart.
He said, "D’you want it pasturize? 'Cause pasturize is best, "
She says, “Ernie, I’ll be happy if it comes up to my chest.”
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That was the name of the milkman I worked for when delivering to Ronnie Corbetts. More tenious links 