Blown patch

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McBentLegs

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Looking for a bit of advice guys and girl.

Completed a small rendering job last week, the side of a garage, hack off old as was all blown and re render.

Scratch coat was layed on over SBR slurry at 5:1 with waterproofer, left it a week before topping it off.

Scratch was solid.

Gave wall a light dampening down before topping off, waterproofer was definitely working.

Topped it off at 6:1:1, floated up lovely, didn't dry too fast etc/

Came back yesterday to fix pipe brackets back on and gave the wall close inspection, all looked fine and solid, not dry and dusty, not blown at all but then noticed a small patch about a foot square where a few hairline cracks were, gave it a tap and this one area is blown.. But everywhere else is solid.

Any idea what could have caused this?
 
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Here's a picture of it scratched and then from yesterday.

I don't do a huge amount of rendering, always terrified of things like this happening, so any advice from the rendering experts would be much appreciated!
 

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Here's a picture of it scratched and then from yesterday.

I don't do a huge amount of rendering, always terrified of things like this happening, so any advice from the rendering experts would be much appreciated!
That the trouble whith float finish smooth finish whith render. The chances are very high for cracking. s**t sand not gauge rhight weather many things can cause it. I think sometimes if you whant a Smoth finish I think your better off going for the new render on market less chance of cracking. Or cheaper options render whith a very ligh brush finish that usually never cracks
 
That the trouble whith float finish smooth finish whith render. The chances are very high for cracking. s**t sand not gauge rhight weather many things can cause it. I think sometimes if you whant a Smoth finish I think your better off going for the new render on market less chance of cracking. Or cheaper options render whith a very ligh brush finish that usually never cracks

Yeh man that's why I tend to steer clear, so much to go wrong rendering.
 
Yeh man that's why I tend to steer clear, so much to go wrong rendering.
Rendering OK dashing brush finish. It just this Smooth finish s**t of a finish you put on and you rubbing up and the spunge gives that perfect finish the trouble is if it dried off in certain places you rub more than you should do and that breaks away from your key. That the beauty of light brush finish you put it on light stible job done. No playing about. My opinion if people whant smooth finish I'd recommend the new Smoth render on the market. If your matching a existing smooth render you tell the customer before you start the chances of it cracking it up to them after.
 
We use Weber ocr every mix is the same we find it easier but it's more expensive than s/c
 
@McBentLegs - many factors can be the cause. Left for a week the waterproofed is set up - all voids crystallized with it, if you gave the scratch a splash of water that can even cause a barrier to the top coat. Even if the render is hallow, it can still last 100years...don’t worry about it :)
 
@McBentLegs - many factors can be the cause. Left for a week the waterproofed is set up - all voids crystallized with it, if you gave the scratch a splash of water that can even cause a barrier to the top coat. Even if the render is hallow, it can still last 100years...don’t worry about it :)
That what I tell them did one last Smoth render front of house perfect job ruled it out gauged everything but warm day found one or two hollow paches. I told them about it and I said no need to woory that stay up for years. And I promise them if it did come off I'd be back to put rhight.
 
@McBentLegs - many factors can be the cause. Left for a week the waterproofed is set up - all voids crystallized with it, if you gave the scratch a splash of water that can even cause a barrier to the top coat. Even if the render is hallow, it can still last 100years...don’t worry about it :)

Cheers matey, makes me feel a bit better!

I'll keep me mouth shut and hope they paint it and don't notice.. If they do I'll just tell them it'll settle lol
 
Looking for a bit of advice guys and girl.

Completed a small rendering job last week, the side of a garage, hack off old as was all blown and re render.

Scratch coat was layed on over SBR slurry at 5:1 with waterproofer, left it a week before topping it off.

Scratch was solid.

Gave wall a light dampening down before topping off, waterproofer was definitely working.

Topped it off at 6:1:1, floated up lovely, didn't dry too fast etc/

Came back yesterday to fix pipe brackets back on and gave the wall close inspection, all looked fine and solid, not dry and dusty, not blown at all but then noticed a small patch about a foot square where a few hairline cracks were, gave it a tap and this one area is blown.. But everywhere else is solid.

Any idea what could have caused this?
You could have overworked that area with the trowel, sometimes if you overwork top coat with sand and cement it can come away from scratch coat
 
You could have overworked that area with the trowel, sometimes if you overwork top coat with sand and cement it can come away from scratch coat
Over work render lol.u lay it on and flatten it off hardly over working it
 
Over work render lol.u lay it on and flatten it off hardly over working it
He said he hasn't done a lot of rendering so probably overworked it and that's why it's come away, have you never seen it happen lol a common mistake
 
How did you get your sand? Sealed bags or open? Could be cat poo I have had a couple of jobs with dead patches due to cat poo in the sand.

All sealed 25kg bags.. definitely no cat poo this time round.

I think I'll put it down to over working it when rubbing up, will bare it in mind for the future!
 
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