Rendered Walls Gone Powdery

B

BigAl93

New Member
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...
 
BigAl93 said:
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...
Click to expand...
What’s the mix?
 
Seen it before with sand and cement ,,, mixed too long with waterproof additive creating weak mix
 
BigAl93 said:
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...
Click to expand...
Hi there my best gues would be to many or to much in the way of additives
 
superspread said:
Did you use the yellow bags of cement, mastercrete? Plus waterproofer?
Like @bof says to many additives if so
Click to expand...
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
malc said:
the sand and cement has dried to quickly. it needs to be hosed down to set the cement.
Click to expand...
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
 
SmoothCriminal said:
Stick with fairy
Click to expand...
Rendered Walls Gone Powdery
 
BryanJ said:
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.
Click to expand...
That's if you've got any teeth left.
 
bof said:
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
Click to expand...
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
 
bof said:
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
Click to expand...
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...
superspread said:
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
Click to expand...
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...
paulf said:
View attachment 58584
Click to expand...
It all makes sense now ☝️
 
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