pebble dashing

[mark5]

Hi can anyone tell me the correct mix for dashing first the scratch coat then top coat. also is cementone waterproofer and plasterciser combined ok for this job. thanks mark
sorry also whats the best sand to use thanks

 

[trowelmonkey1]

hi mark,

firstly, i'm not a render pro but here is what i understand:

combined plasticiser and waterproofer is fine, probably go as far as to say recommended.

ratio for stones in the first coat? maybe misunderstood but you wouldn't put them in the first/scratch coat, which should be a mix of 4:1 (4 sand:1cement) some guys like to put 1 of lime in the mix too, as it helps workability, reduces cracking and improves adhesion.

float coat on top of that should be 5:1, again with lime if you choose to.

sand should be a good quality WASHED plastering sand, get bad sand and you'll end up with cracks, as a rule it should contain no more than 10% foreign particles/silt, i used buildbases mixed plastering sand last week and got a few hairline cracks, tested the sand by putting into a jar with water and shaking, left it to settle and lo and behold...almost 30% silt! shouldn't have trusted them, wickes do small bags but never tried theirs.

 

[roughcaster]

combined plasticiser and waterproofer is fine, probably go as far as to say recommended.

ratio for stones in the first coat? maybe misunderstood but you wouldn't put them in the first/scratch coat, which should be a mix of 4:1 (4 sand:1cement) some guys like to put 1 of lime in the mix too, as it helps workability, reduces cracking and improves adhesion.

float coat on top of that should be 5:1, again with lime if you choose to.

sand should be a good quality WASHED plastering sand, get bad sand and you'll end up with cracks, .

I would agree with everything T/Monkey says here in his reply.

Roughcaster.

 

[trowelmonkey1]

woo hoo! thx RC!