Rendered Walls Gone Powdery

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BigAl93

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Hello there, as the title says Ive rendered a whole basement out after tanking the walls and the final coat of render has gone powdery. At first I realised this could be because I was trying to dry it overnight with a gas blower on it.

For the next room I tried without a gas blower on it. Same story, scratch coat is always solid yet. My final coat was powdery again?! Which is a shame really as all the levels were spot on had a good eye for it. But have basically wasted a week now. Have been desperate for solutions but Ive been unable to find any.

Is there some solution that needs to be put on the scratch or do I still render on to it when its still a bit wet.

Cheers Guys...
 
Hello there, as the title says Ive rendered a whole basement out after tanking the walls and the final coat of render has gone powdery. At first I realised this could be because I was trying to dry it overnight with a gas blower on it.

For the next room I tried without a gas blower on it. Same story, scratch coat is always solid yet. My final coat was powdery again?! Which is a shame really as all the levels were spot on had a good eye for it. But have basically wasted a week now. Have been desperate for solutions but Ive been unable to find any.

Is there some solution that needs to be put on the scratch or do I still render on to it when its still a bit wet.

Cheers Guys...
What’s the mix?
 
Seen it before with sand and cement ,,, mixed too long with waterproof additive creating weak mix
 
Hello there, as the title says Ive rendered a whole basement out after tanking the walls and the final coat of render has gone powdery. At first I realised this could be because I was trying to dry it overnight with a gas blower on it.

For the next room I tried without a gas blower on it. Same story, scratch coat is always solid yet. My final coat was powdery again?! Which is a shame really as all the levels were spot on had a good eye for it. But have basically wasted a week now. Have been desperate for solutions but Ive been unable to find any.

Is there some solution that needs to be put on the scratch or do I still render on to it when its still a bit wet.

Cheers Guys...
Hi there my best gues would be to many or to much in the way of additives
 
the sand and cement has dried to quickly. it needs to be hosed down to set the cement.
 
Did you use the yellow bags of cement, mastercrete? Plus waterproofer?
Like @bof says to many additives if so
It's the over mixing mate , people think it makes no difference
Labourer's left it turning to make it nice and fluffy lol , pay peanuts , blind leading the blind etc

Poster says just SBR
the sand and cement has dried to quickly. it needs to be hosed down to set the cement.
Second time was without the blower , in a basement it's gonna hold it's moisture , do you think the scratch has sucked it dry
 
Stick with fairy
cadcrunch08.png
 
The best thing about crunchy bars after you finish there is always

The best thing about crunchy bars, when you finish there is always some stuck in your teeth for a bit extra treat.
That's if you've got any teeth left.
 
It's the over mixing mate , people think it makes no difference
Labourer's left it turning to make it nice and fluffy lol , pay peanuts , blind leading the blind etc

Poster says just SBR

Second time was without the blower , in a basement it's gonna hold it's moisture , do you think the scratch has sucked it dry
Yea over mixing added t with the plasticer in the yellow bag cement and waterproofer the mix goes like angel delight because there’s not enough water to set it hard
 
It's the over mixing mate , people think it makes no difference
Labourer's left it turning to make it nice and fluffy lol , pay peanuts , blind leading the blind etc

Poster says just SBR

Second time was without the blower , in a basement it's gonna hold it's moisture , do you think the scratch has sucked it dry
Correct I just used SBR with ordinary brown paper cement bags.

Also I had a 17 year old kid mixing for £40 a day I want my moneys worth...
Yea over mixing added t with the plasticer in the yellow bag cement and waterproofer the mix goes like angel delight because there’s not enough water to set it hard
It was a very fluffy mix to be fair.
Im going to have to hack it all off and mix myself one the next one...
It all makes sense now ☝️
 
Labouring in the plasterers trade is a skill in itself - getting the mix right is 50% of the job.
 
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