Making sand and cement render to look like lime render

[Jonny]

Hi.  I’m starting to look through the details of a barn conversion that hopefully we will be completing on over the next couple of months all being well with planning permission. 

 

The existing barn will be demolished and a timber frame with external block skin will be put in place. We would like to keep the feel of the existing lime render and stone plinth barn. We will be aiming to use as much as the stone as possible to complete the plinth and then there will be standard cement block over the top of this. Initial thoughts where that we would require lime render over the top, however on speaking to a local structural engineer (he has completed his dissertation on the detrimental effects of sand cement render on historic buildings)he suggested that we might be able to work sand and cement to make it look like lime render. 

 

I’m a little sceptical about this and it is not something I’ve heard of before, but I’m reaching out to you guys to see where you’ve heard or seen this in practice. 

 

For context we currently live in a modern block house with sand and cement render but unfortunately it hasn’t been done very well and picks up every single dip in many lighting conditions. I love the rustic look, softness and unevenness of lime render so I don’t want it to just look like a badly completed sand and cement render any advice or shall I just continue with the lime render as originally planned?

[JohnMo]

I suppose it is likely render was originally put on an uneven substrate - rubble etc. so likely you will never get a flat finish. Leave the past behind - you are doing a new build embrace it

Edited July 31 by JohnMo
Total rewrite

[nod]

You can do this with a 4-2-1 mix 

No plastersizer 

[Mike]

On a block wall, it's going to be tricky to get a rustic finish, however using lime paint helps as it ages by turning powdery and weathering off, unlike modern vinyl paints.

 

FWIW one of the best fake-rustic new-builds I've seen used deliberately roughly-laid brick, bag-rubbed with thin render, then limewashed.

[Redbeard]

If you genuinely want uneven render on 'even' blocks you could tack expanded metal on with the odd spacer here and there, and apply the render more with rubber gloves than trowels.