Rendered Walls Gone Powdery

[BigAl93]

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...

 

[Vincey]

Sounds like a right shitter there mate what’s the materials you using

 

[Cockney1]

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?

 

[Deleted member 32554]

Seen it before with sand and cement ,,, mixed too long with waterproof additive creating weak mix

 

[Monkey Boy]

I was trying to dry it overnight with a gas blower on it.

 

[Trppy]

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

 

[malc]

the sand and cement has dried to quickly. it needs to be hosed down to set the cement.

 

[BigAl93]

Seen it before with sand and cement ,,, mixed too long with waterproof additive creating weak mix

We were adding SBR to the mix

I know, we had an inspector coming the next 2 days and wanted it dry...
I wasnt there but apparently he laughed

 

[superspread]

Did you use the yellow bags of cement, mastercrete? Plus waterproofer?
Like @bof says to many additives if so

 

[Deleted member 32554]

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

 

[SmoothCriminal]

First coat still my have been thirsty! To much additives etc. Stick with fairy

 

[paulf]

Stick with fairy

 

[SmoothCriminal]

Ah the old bubble theory....

 

[BryanJ]

The best thing about crunchy bars after you finish there is always

View attachment 58584

The best thing about crunchy bars, when you finish there is always some stuck in your teeth for a bit extra treat.

 

[paulf]

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.

 

[superspread]

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

 

[BigAl93]

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...

View attachment 58584

It all makes sense now ☝️

 

[smoother09]

Sounds like a wind tbf

 

[Lastlaff]

Labouring in the plasterers trade is a skill in itself - getting the mix right is 50% of the job.