rendering

[batesy2]

I am rendering a breeze block shed and would like to know the thickness the render should be I have unibonded the wall and I have 13mm beading, I would like to know what materials I should use and what ratio the mix should be....

[Bradleybuild]

Is it cement based render??
I guess it is
use sharp sand and soft sand mixed together 50:50
use this with 1 cement to 5 of sand mix, add a little plasticiser
damp your wall down with a mist of water and slap it on about 5mm thick(its easier to put some strips of wood vertically at 3 foot spacings to act as trammel bars if youve never rendered before and use those trammels to guide you with a darby(big float) or pice of planed timber
when its going off scratch the surface 2-3mm deep all over and leave it till it can support another coat, put the top coat on and allow to become semi-hard and then sponge in a circular fashion all over the wall
(remove the vertical wood and fill with same mix befor sponging)
hope it helps
brad

[roughcaster]

The only problem with using strips of wood as guides when rendering, is when the render has got to the "nearly off" stage ready for the sponge,when you remove the wooden strips and fill up where they have been with mortar,THAT mortar will be a long way from the "nearly off" stage of the surrounding render and these filled up strips will always be noticeable in the finished wall. But if you use the strips of wood early on,level the wall with,in this case the darby/straight edge,remove the strips right away and fill up the channels with mortar right away,it will all go off at the same time,and can be floated and sponged at the same time and give an even looking finish.Plastering a wall with a floating coat this way would not be a problem because the finishing plaster would cover any defects in the undercoat.

Roughcaster.

[jaguar1]

Is it ok to use plasticicer together with a little pva when mixing the sand and cement prior to rendering ??