I have around 10 m2 of external blockwork wall that I want to render. The problem is although I'm pretty neat with joinery and internal work I've never tried rendering and no local builders / plasterers seem interested in the present market.

I would therefore really appreciate advice starting from the very basics (!). Questions I have are:

Does it need a primer coat?
What are the all the constituents for the scratch coat which I assume is the first of two coats to go on?
How do I apply it, eg top to bottom of vice versa, what thickness, how do I get the scratch coat finish?
How big an area should I work with?
Ditto top coat which I assume is the second and final coat which the chips will be applied to?
How do I apply the dry harling chips and what quantity should I buy (it's what we call a Skye marble chip)?

The wall is 6" block on flat in good, dry condition, varying from 0.3m to 1.7m in height.

I know I'm asking a lot. I'm in the Highlands BTW and my neighbour has a mixer.

Thanks in advance.

Martin

Hi Emmellar, You will need a 4:1 mix for the scratch coat, thats 4 plastering sand to 1 cement. I'm left handed so i start top right, roughly do a metre long panel at a time. it needs to be around 10mm thick. once the whole wall has been scratched, you need to key it ready for the topcoat. You can buy a scratcher to do the job http://cgi.ebay.co.uk/R-S-T-Soft-Touch- ... _Equipment or make your own out of a few nails and a couple of bits of wood.

to key it you need to run the scratcher horizontally all the way along the wall. do not go all the way through to the blockwork. now let the render cure for a couple of days, as many as possibly ideally. for the topcoat you need a 5:1 mix this time. apply the same way as the scratch, again to around 10mm thick. wet the wall before you start so the scratch coat doesn't suck the water straight out of the top coat. this time once you have done a metre wide panel, you will need to rule it off using a feather edge. when you have ruled it, fill any hollows and move onto the next panel. once the whole wall is complete you will have enough time to wash the mixer and your tools off before you start to rub up.

to rub up you will need a float, preferably worn in, and a sponge to finish the wall. when the render is starting to firm up but not quite starting to set, starting at the same place you started the last 2 times, rub the wall with the float in a small circular motion, filling and small holes with any left over render you've got. don't keep going over the same part. once the whole wall has been rubbed up you then do the same actions with a damp sponge. keeping it clean.

if you arent very confident with the large area, you could put stop beads along the wall vertically to break it up into smaller sections but it would look alot better without them.

i think i've covered everything but if anyone can add anything feel free.

bit of waterproofer in the scratch coat to give him time on the float coat maybe?

when i'm floating i start in the opposite corner to skimming, if you can find a vid on youtube of someone laying on a render/float coat this will help you massively when you do the work, seeing how it is done, each trowel full laying into the last, it'll improve the job no end for you.

_________________
“He who asks a question is a fool for five minutes; he who does not ask a question remains a fool forever”
Abingdon Plasterer

how could i forget the admixtures. you'll need plasterciser in both coats, it makes it easier to work. and waterproofer in the scratch, you could also add a lime if you really want to, add the lime the same ratio as cement.