Sand and cement render

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Nathanrose

New Member

• Jul 26, 2015

• #1

Hi guys,

Just a bit of advice really rendered a wall the other day was on an existing rendered wall hacked off back to block work believe to be thermalite/celcons sbr'd before scratch coat then 5-1 scratch, dampened down wall before top coat at 51/2-1-1. Cracked in a few places and blown in a couple. was kept damp after top coat applied. ant advice on the causes and possible fixes would be appreciated. Is there any chance remove blown patch in ? Or possibly cover in thin coat of acrylic render can that go straight over smooth sand and cement ?

Thanks

 

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Nathanrose

New Member

• Jul 26, 2015

• #2

Plastering sand was used for both

 

leebo02

Well-Known Member

• Jul 26, 2015

• #3

hello mate, dont quite understand what mix your top coat was, did you put any additives in scratch coat, how long did you leave scratch coat before topping, i take it there was plenty of key for top coat, if you go over the blown areas they are still gonna be hollow

 

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Nathanrose

New Member

• Jul 26, 2015

• #4

Hi mate,

Waterproofer in scratch coat.
Top Coates 5 1/2 sand 1 cement 1 line
Scratch was left a couple of days. How about removing the blown then going over any ideas ? Thanks again

 

leebo02

Well-Known Member

• Jul 26, 2015

• #5

yeah you could do that

 

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malc

TPF Special Forces

• Jul 26, 2015

• #6

what size is the blown area?

 

Jgreenplastering

Private Member

• Jul 26, 2015

• #7

Did you let the SBR dry?
I'd take out the hollow re do with a SBR slurry first then wack a tyrolean coat on it to finish

 

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Nathanrose

New Member

• Jul 27, 2015

• #8

Hi Malc probably 3 or 4 patches 40cm2 roughly.
Yes sbr was left to dry then scratch on top thanks mate.

 

Jgreenplastering

Private Member

• Jul 27, 2015

• #9

SBR shouldn't be left to dry. It doesn't re emulsify like PVA.
It basically becomes water proof so then the scratch would have the suction to bond properly.

Take the bits off and use a SBR slurry then scratch again, that s help it bond

 

johniosaif

Private Member

• Jul 27, 2015

• #10

,I'd sbr scud it,
Scratch it 6/1 ,float it 6/1/1 a few days later or a monolithic coat depending on weather suction etc.

 

irish_spread

Private Member

• Jul 27, 2015

• #11

Id take the money and run

 

Marshy

Private Member

• Jul 27, 2015

• #12

johniosaif said:

,I'd sbr scud it,
Scratch it 6/1 ,float it 6/1/1 a few days later or a monolithic coat depending on weather suction etc.

Click to expand...

Not like you John to scud something ??

 

irish_spread

Private Member

• Jul 27, 2015

• #13

I love it when plasterers ask why did it fall off ?

 

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Nathanrose

New Member

• Jul 28, 2015

• #14

Thanks for the replays guys, think going to remove all top coat and reapply is it best to sbr scud the scratch first before reapplying top coat ?

 

scottie5

Private Member

• Jul 28, 2015

• #15

irish_spread said:

I love it when plasterers ask why did it fall off ?

Click to expand...

Generally gravity, witchcraft or bigger boys who ran away are to blame.

 

carlos

Private Member

• Jul 28, 2015

• #16

Re topping will not help the scratch coat stick any better lol

 

Arti

Well-Known Member

• Jul 28, 2015

• #17

irish_spread said:

I love it when plasterers ask why did it fall off ?

Click to expand...

Falling damp

 

beader

Private Member

• Jul 28, 2015

• #18

irish_spread said:

I love it when plasterers ask why did it fall off ?

Click to expand...

surly a plasterer could work it out for him(or her) self and know the best way to fix it or has this place just made people lazy . just a thought