Hello All, newbie here.
I am seeking any views on how the render over mesh on my 1930s semi was done.
It's in three layers, which is expected.
The innermost layer, which envelops the mesh and backs up against a bitumen-felt backing sheet, is almost white where it is smooth and touched the backing sheet. If broken, it looks a little less white, containing what looks like a light grey grit/sand. It's fairly soft, and can be scraped back using a metal tool. I believe it's lime render. Most of the house brickwork/internal plastering is done with lime render, which varies from white to a sort of slightly beigey colour in some places, especially if exposed.
So, no mystery there either.
The final two layers, both thinner than the (supposed) lime coat, are both noticeably darker, greyer. Not only that, they are rock hard. My little pointing trowel, which will happily chip away at the lime render behind it, won't touch them.
There is a layer of pebble dash on the top layer. It's very sound, held on hard. The reason this render failed was that the galvanised mesh backing finally rusted out and cracks developed. The mesh is over some studwork between ground and first floor bay windows.
I'm thinking the two thinner, outer layers, being darker grey and rock hard, are strong cement renders? However, I didn't think this type of render construction was good practice. Each layer must be weaker than the last etc. I also though using dissimilar types of materials together like this is verboten.
Has anyone come across this kind of render system before? I'd prefer to duplicate it, but need to understand it first!
PS: I suppose since it's on mesh the soft scratch coat in lime mortar might be for flexibility to accomodate movement, the hard top coat(s) resists the weather, but it still seems backwards to the advice I normally see which has the stronger mix as the scratch coat.
I am seeking any views on how the render over mesh on my 1930s semi was done.
It's in three layers, which is expected.
The innermost layer, which envelops the mesh and backs up against a bitumen-felt backing sheet, is almost white where it is smooth and touched the backing sheet. If broken, it looks a little less white, containing what looks like a light grey grit/sand. It's fairly soft, and can be scraped back using a metal tool. I believe it's lime render. Most of the house brickwork/internal plastering is done with lime render, which varies from white to a sort of slightly beigey colour in some places, especially if exposed.
So, no mystery there either.
The final two layers, both thinner than the (supposed) lime coat, are both noticeably darker, greyer. Not only that, they are rock hard. My little pointing trowel, which will happily chip away at the lime render behind it, won't touch them.
There is a layer of pebble dash on the top layer. It's very sound, held on hard. The reason this render failed was that the galvanised mesh backing finally rusted out and cracks developed. The mesh is over some studwork between ground and first floor bay windows.
I'm thinking the two thinner, outer layers, being darker grey and rock hard, are strong cement renders? However, I didn't think this type of render construction was good practice. Each layer must be weaker than the last etc. I also though using dissimilar types of materials together like this is verboten.
Has anyone come across this kind of render system before? I'd prefer to duplicate it, but need to understand it first!
PS: I suppose since it's on mesh the soft scratch coat in lime mortar might be for flexibility to accomodate movement, the hard top coat(s) resists the weather, but it still seems backwards to the advice I normally see which has the stronger mix as the scratch coat.
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