Internal render not set

[loren669]

oh sorry stevethespreader,

the render was still wet as when you pushed your finger on it today it fell away from the wall and was wet in colour and when scaping the wall, the wall was damp still. The dry crumbly bits were the bits that fell on the floor that had dried overnight were crumbly like sand again.

Also when i had scraped all the render off, it dried just like sand on the floor.

None of it seemed to cure, there was no cured lumps.

 

[chris_o]

My opinion is that the water has been sapped out of your mix too quickly

 

[vinn]

At any stage did you apply an agent such as the French equivalent of PVA or SBR?

So you applied a scratch coat.
And then went over it with a 10mm(?) 4:1 mix of sand and ordinary grey cement.
This coat was scratched & allowed to dry?
You then took the suction out of the first coat, and then went over it with a 10mm(?) white cement coat?
Presumably, you rubbed up the white coat as a finished surface?

Again I'm presuming that whatever is falling off the wall is both 10mm coats?
Do they come off separately or stuck together as one piece?
Is the scratch coat still sticking to the wall?

If you can, you would be best to leave well alone for a couple of weeks, and then test the dryness of the wall.
Abandon the bags of powder that you now have.
Carefully examine the exterior render or pointing.

 

[loren669]

Hi Chris_o, its a possibility but no sure about that.

Hi Vinn,
No i didnt add any PVA or SBR, just a dash of a feb mix.

No, i applied a scratch coat 10mm 5:1 mix of sand and ordinary grey cement over the blockwork wall.
3 days drying time.
Then took the suction out of the first coat, and then went over it with a 10mm 4:1 sand and white cement coat
and rubbed up the white coat as a finished surface (ish)

what is falling off the wall is the white sand and cement 10mm coat.
The scratch coat is still solid and firm.

I have done what you said and abandoned the bags of powder that caused the problem and used a new bag and re-rendered the wall this lunchtime.

NOTE The mix today was working like usual and not a sticky consistency and sticking to everything.??? !!

I will post tomorrow if this has hardened up or not !! fingers crossed for me please

 

[roy c]

If you start off with a 4-1mix then you should make sure the next coat is weaker than your first coat (5-1) as opposed to a 5-1 coat then a 4-1 coat as you are putting a stronger mix on top of a weaker mix.. What are you using to gauge your mixes ...

 

[loren669]

I apologise Roy c, i got the mixes the wrong way round. the grey scratch coat was 4:1 and the white top coat was 5:1.
well done for seeing that typing error
I use a bucket as my gauge, full and levelled off. Dont know any different method so definitely open to pointers

 

[vinn]

FWIW, your first 10mm coat was not the scratch coat.
The scratch coat is a very tight coat 2mm - 4mm tops, sometimes its a kind of slurry.
The backing coat goes on the scratch coat.

 

[loren669]

Evening Vinn,
fwiw??
That has totally gone over my head im sorry. good job im not doing it to earn money eh!! Hope what ive done stays on then!

 

[roy c]

The scratch coat is usually the first coat on the wall then the float coat then skim, but some times you have to "Dub" it out first to get an even scratch coat so you can float it. Well that's the way I have always done it !! But I am willing to learn "new" methods or am I missing something?

 

[vinn]

There's nothing new so I doubt that you are missing anything new but you do seem to be a bit confused and paranoid - why the quotation marks, and the exclamation marks, and the introduction of a capitalised "Dubb"?

FWIW: I wasn't aiming at you, why should I be, the post was directed at the OP, and I'm aware that my scratch coat and your scratch coats have different definitions - but i use the terms that I was taught & have always used.
Building trade terminology has many local differences - and long may it be so.


Tell me, what do you call it when you apply a very tight first coat as described in my post above?

 

[roy c]

I think I have explained myself so other people can understand what I said, so as for your quotes in your opening sentence I never get confused and paranoid. I grew out of all that years ago and say it as it is. And don't bother trying to bait me as I don't really worry about my grammer now as I am to old in the tooth to worry about how I write but as long as I put up good useful info I am not too bothered about my typo's... P.S. it's Dub...

 

[vinn]

No baiting or references to anything new around here.
What you've written is not an explanation its an evasion - a bit sad really.

My question still stands?

 

[roy c]

Sad man...

 

[vinn]

What a strange answer to an innocent technical question - especially when you are claiming to "explain yourself so other people can understand what you say"?

 

[Nige F]

Innocent ? So was Dr. Shipman. Perhaps Vinn should go back to his head doctor.