Hello, The pebbledash above my bay window (30s semi) had cracked extensively, revealing a galvanised mesh that was now beyond rust.
So, I have knocked all the exterior render off the bay and now have stainless steel expamet mesh ready to start the repair.
I understand that I should use stainless nails and tie wire with s/s mesh, not galvanised.
That I should overlap sections of mesh by four inches. That the mesh is backed by 1/4" thick wooden battens to allow the render to penetrate the mesh and hang on.
That these battens are also to hold the bituminised felt sheet* behind the mesh in place against the wooden studding behind it (I guess I could use 1200 ga polythene sheet too).
*Thinking of 'undertile felt' from B&Q - similar thickness to the original, though the B&Q stuff is lightly sanded.Things I am less certain about - my house is from 1938 and has lime plaster inside and lime mortar between the bricks, it's quite white in appearance and the mesh had this in it too - but there appear to be three coats of render, the inner one fairly white, the next a little darker, the third with all the pebbles stuck in it. I am thing the base coat is not pure lime mortar though? More likely 1:1:5 lime:cement:sharp sand? What about coarse sand - is that better?
I believe the layers should get weaker as you go out, so the next layer might be 1:1:6?
Not sure about the pebbledash layer - needs to be able to take pebbles though having tried this once they just seem to bounce off ;0)
Also not sure about 'bonding' to the mesh and/or the brickwork at the edges with pva or 'sbr' slurry?
Is the initial 'pricking' coat to the mesh done in a special way or is it just a thin coat to get the 'tongues' of render stuck through the back?
Also not sure about putting waterproofer in the render - after all, lime mortar is breathable, so is cement/lime mortar to a certain extent. I don't want to trap water where a lime render could have 'breathed' it out so to speak.
Any comments/advice/tips??
Andy