Concrete floor levelling - Cement / PVA slurry?


M

Mike

Hi
Found this great old thread which seems to be the answer to my problem
of levelling a concrete floor where thickness required is too much to
use standard self-levelling compound and too little for standard
screed. Relevant bits:

" The only real solution is to bring the whole floor up to the same
level.
There are lots of ways of doing this for a 10mm level difference. You
could use a runny concrete slurry as a thick self levelling compound
(most self levelling compounds can only be used up to around 3-4mm
thick,
which is why you have to make your own slurry)."
"We did this in one of the rooms in our last house. Just mixed up a
slurry using cement and fine sand (1:4), using PVA in the gauging
water
(around 1:4 PVA:water). Worked great."

Just wondering if anyone has tried the 'PVA cement slurry' as
described and knows how wet you can get away with making the mix
without problems. My plan is to mix it properly runny so that it does
actually self-level but unsure if this will compromise set strength? A
ratio of pva water : dry mix would be really useful if anyone knows?
Thanks in advance for any help.
 
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S

Stuart Noble

Mike said:
Hi
Found this great old thread which seems to be the answer to my problem
of levelling a concrete floor where thickness required is too much to
use standard self-levelling compound and too little for standard
screed. Relevant bits:

" The only real solution is to bring the whole floor up to the same
level.
There are lots of ways of doing this for a 10mm level difference. You
could use a runny concrete slurry as a thick self levelling compound
(most self levelling compounds can only be used up to around 3-4mm
thick,
which is why you have to make your own slurry)."
"We did this in one of the rooms in our last house. Just mixed up a
slurry using cement and fine sand (1:4), using PVA in the gauging
water
(around 1:4 PVA:water). Worked great."

Just wondering if anyone has tried the 'PVA cement slurry' as
described and knows how wet you can get away with making the mix
without problems. My plan is to mix it properly runny so that it does
actually self-level
Alas, nothing sets level by itself. If it's too runny, the sand and
cement will settle out under the water in a random fashion.
IME the 1:4 PVA works fine, even down to a feather edge, but it has to
be thickish i.e. it just about slides off a metal trowel and lands with
a thud rather than a splat (very technical :)).
I suggest using the bagged general purpose mortar for this, or
plasterers sand if you're mixing your own. Sharp sand can be a bit too
coarse.
The most useful tool for levelling is a length of wood a foot or so
shorter than the width of your room

but unsure if this will compromise set strength? A
 
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J

John Rumm

Mike said:
Just wondering if anyone has tried the 'PVA cement slurry' as
described and knows how wet you can get away with making the mix
without problems. My plan is to mix it properly runny so that it does
actually self-level but unsure if this will compromise set strength? A
ratio of pva water : dry mix would be really useful if anyone knows?
The latex mix you get from wickes can be used mixed with sharp sand to
fill deeper sections first. Then just screed the lot with a normal latex
mix after that has started to go off. I have feathered that down to
nothing without any problems.
 

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