New block work

B

brimplas1

Well-Known Member
I've a garden wall to render and am just wondering best ratio? Done 15 yrs of internal stuff and odd externals but always been brick work.... The wall is a 7.3n hollow block.... Was thinking 4-1 scratch and 5-1-1 top.... Is this ok ?...

Ta in advance...
 
4:1 is too strong it will probably craze. 5:1 scratch sharp sand. 5-6:1 second coat with 1 of the sand soft. Let the scratch fully cure.

Better still use a modern render like a base coat then ocr. Garden walls are usually built wrong for rendering and are problematic. I stopped doing them, not worth the comeback.
 
One coat big lash up don’t matter what the ratio is , rule it off once, don’t bother levelling it or filling in hollows and sponge it to death.
Get paid and block costumers number
 
Rigsby said:
4:1 is too strong it will probably craze. 5:1 scratch sharp sand. 5-6:1 second coat with 1 of the sand soft. Let the scratch fully cure.

Better still use a modern render like a base coat then ocr. Garden walls are usually built wrong for rendering and are problematic. I stopped doing them, not worth the comeback.
Click to expand...
Thanks rigsby... The wall is brand new, whilst it has no dpc it does have 4 courses of engineering bricks so don't think damp will be an issue... Thought about Ocr but im sure id seen on here lots of people had had issues with cracks ..
 
brimplas1 said:
Just looking at that myself... Cheaper than normal ocr also....
Click to expand...

Used a bag the other day on a porch ceiling. TBH, first time I've done any external render, but it mixed nice and went on well.

Anyway, sorry to hijack mate, but just interested in a reasonably failsafe method too.
 
ChrispyUK said:
Used a bag the other day on a porch ceiling. TBH, first time I've done any external render, but it mixed nice and went on well.

Anyway, sorry to hijack mate, but just interested in a reasonably failsafe method too.
Click to expand...
No problem, ive done years of internal on brick but little external and never on block..... Im thinking of using ocr, mesh the 1st coat and scratch it... Let it cure then top it with ocr.....
 
At this time of year you will be struggling with setting times, sliding and sagging.

I would do two coats in either s&c or ocr letting the scratch coat cure fully and the second coat being 6mm with Wickes hardener added. It will rub up full of water though so different to summer conditions.

Myself I would use Parex Parmurex being waterproof and put on late as and ibar it back to flat next morning. No annoying sagging and a drier surface sponge finish.

Stop bead under the copings and beaded edges so you can bar or rule off too and it will be flat
 
Rigsby said:
At this time of year you will be struggling with setting times, sliding and sagging.

I would do two coats in either s&c or ocr letting the scratch coat cure fully and the second coat being 6mm with Wickes hardener added. It will rub up full of water though so different to summer conditions.

Myself I would use Parex Parmurex being waterproof and put on late as and ibar it back to flat next morning. No annoying sagging and a drier surface sponge finish.

Stop bead under the copings and beaded edges so you can bar or rule off too and it will be flat
Click to expand...
Thanks pal, no need to rend aid or mesh then ?
 
Shouldn’t need it but if you want it to be extra sound then yes. Sbr cement slurry for s&c rendaid or equivalent for ocr..
 
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