Latex screed + no DPM concrete = localised bond failure
Tim S
Just been down to the Bunglow to gauge out the kitchen floor.
This started life as +/-15mm with significant bumps which would have made
tiling impossible (unless I used mosaic!!!).
Anyway, whilst marking out the low spots that need more latex, I found a few
areas where the bond had failed (cracking of the screed and hollow sounding
noises when tapped). Worst area was about 1m x 40cm, and a few other areas
were smaller. About 2-3m2 out of 19m2 had a problem, everywhere else the
screed was sound.
This was a contracted out job, so obviously I'll be raising it with the chap
who did it - he's coming down Thursday or so.
But, in order to be able to have an intelligent discussion with him, would
anyone be prepared to pass an opinion on my theory, which is:
The latex compound didn't take properly due to the surface either being a
bit damp or friable or both. In either case, chucking down some stabiliser
might seem to be a good idea, before re-applying compound to the affected
areas. I'm thinking a good soaking in SBR (as PVA won't be so good in damp
conditions).
I plan to overseal the whole floor with AquaSeal "Aqua Stop" (on
recommendation) before tiling, which will sort out any damp issues - so all
I have to worry about is that the levelling compound maintains a decent
bond to the substrate.
Cheers
Tim
Stuart Noble
IME 2 part latex floor screed is like shit to a blanket, which is why
it's used to firm up friable surfaces. Existing dampness should make no
difference, as the product is water based. However, it IS expensive, and
there are cheaper one part, cement based floor screeds. I hope the
contractor didn't cut corners.
Tim S
> IME 2 part latex floor screed is like shit to a blanket, which is why
> it's used to firm up friable surfaces. Existing dampness should make no
> difference, as the product is water based. However, it IS expensive, and
> there are cheaper one part, cement based floor screeds. I hope the
> contractor didn't cut corners.
Hi Stuart,
I don't believe he would knowingly cut corners - we have a long standing
association as his firm do lots of work where I work.
He's coming in tomorrow to have a look. He did mention that the product he
bought, which used to be 2 part was now one part, with the "2nd part" mixed
in dry to the 1st part. Seemed to be new to him. I'll get the brand
tomorrow. Obviously it was a product variation that he didn't expect -
maybe someone was telling him round objects.
Well, if he's used an inferior product it will be down to him to sort it
out. He said he did put lots of stabiliser down.
Cheers
Tim
Tim S
That was exactly the sort of information that helps me look at this
objectively...
John Rumm
All the latex ones I have used recently (typically Wickes) have been one
part - just add water. They seem to bond pretty well IME. They do a
cheaper one that does not include the "latex" in the title. I have not
tried that, so don't know how it compares.
--
Cheers,
John.
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Tim S
> All the latex ones I have used recently (typically Wickes) have been one
> part - just add water. They seem to bond pretty well IME. They do a
> cheaper one that does not include the "latex" in the title. I have not
> tried that, so don't know how it compares.
>
Thanks John,
That sounds the same as the way he described. He did wonder if the bond
failure might be one level down in the original screed, which apparantly is
not very thick.
The key thing that matters is whether it will fall off or not. I'm sure,
that if it turns out that we have 1.5cm of stable "skin" that's failed a
bond lower down, then it's probably not going to fall off and with the
weight of the floor covering on it, it's not going to lift off either.
If it's the latter, I'll drill and epoxy some 2" stainless stud in to lock
it to the base slab. Bodge: possibly, but when the alternative is hack up
19m2 of floor and pour 2 tons of concrete into the room plus a ton of
screed, then needs must. It's very easy to be a perfectionist, in which
case, might as well knock the house down and start again. What matters is
whether it works, rather than how :->>>
Shall see what tomorrow brings...
Thanks chaps!
Tim
Stuart Noble
> Stuart Noble coughed up some electrons that declared:
>
>> IME 2 part latex floor screed is like shit to a blanket, which is why
>> it's used to firm up friable surfaces. Existing dampness should make no
>> difference, as the product is water based. However, it IS expensive, and
>> there are cheaper one part, cement based floor screeds. I hope the
>> contractor didn't cut corners.
>
> Hi Stuart,
>
> I don't believe he would knowingly cut corners - we have a long standing
> association as his firm do lots of work where I work.
>
> He's coming in tomorrow to have a look. He did mention that the product he
> bought, which used to be 2 part was now one part, with the "2nd part" mixed
> in dry to the 1st part. Seemed to be new to him. I'll get the brand
> tomorrow. Obviously it was a product variation that he didn't expect -
> maybe someone was telling him round objects.
>
I somehow doubt that there is any dry form of SBR because it's basically
a type of rubber.
Also, the 2 part stuff I've used isn't cement based. The powder is the
same colour, but it behaves very differently, and there appears to be no
chemical reaction with water. It seems to be some kind of inert mineral
that is bonded by the polymer, but there is no "cure" as such. Don't
know how relevant that is to your problem, but it might be interesting
to see what your contractor thinks.
Stuart Noble
No need :-)
Tim S
> I somehow doubt that there is any dry form of SBR because it's basically
> a type of rubber.
>
> Also, the 2 part stuff I've used isn't cement based. The powder is the
> same colour, but it behaves very differently, and there appears to be no
> chemical reaction with water. It seems to be some kind of inert mineral
> that is bonded by the polymer, but there is no "cure" as such. Don't
> know how relevant that is to your problem, but it might be interesting
> to see what your contractor thinks.
They used this (Cementone Cempolatex 1 pack)
http://www.bostik.co.uk/diy/product/33
OK. after some discussion this morning, we think the hollow sounds are
coming from lower down (ie the next level of original screed is dodgey). I
think that's far enough down that it's not likely that the screed will
collapse or flake. I'll leave it alone, probably. The floor will be bare
for a couple of months so plenty of time to see how it goes. A degree
of "carefully engineered bodgery" is acceptable, as long as it is basically
sound.
Thanks to my efforts in marking out the contours, they primed the areas with
PVA and dropped a fair amount of extra compound bang in the middle of the 3
remaining hollows and feathered them in. That should be good enough to lay
insulation on (subject to a further check when it's dry). Also they showed
me how to mix and apply the screed so I'm set up to make any minor
alterations and repairs later (they're helpful like that).
Cheers
Tim
Tim S
which tells me Cempolatex 1 pack is 17.35 inc VAT.
Whereas Travis Perkins website tells me it's 29.98 PLUS VAT.
Hmm - suggestions involving barge poles and orificial insertion come to
mind. Pity Beers are only Liverpool way - but it does give a very good
indication of how much to negotiate the local supplier down to.
My builder paid about 20 quid per bag ex VAT, so the Liverpool to
SouthEastern compensating factor seems to be Beers plus about 30%.
Very useful information, to me at least (and hopefully someone else). I'll
use them as a guage for all general materials...
Cheers
Tim
A.Lee
> While we're on the subject and I was searching for Cempolatex, I noticed:
>
> www.beersltd.co.uk
>
> which tells me Cempolatex 1 pack is 17.35 inc VAT.
>
> Whereas Travis Perkins website tells me it's 29.98 PLUS VAT.
TP are comical in their pricing.
I avoid them now.
Last time I went to the local one, I needed 2 18" plain slabs. I pay
£1.34 inc. vat for these at the other merchants.
Now TP have a loading sytem, where you load up, take a ticket into the
office, then pay. The yardsman does not know the prices.
So, loaded the 2 slabs, went to pay, was told they are £2+ vat. each. I
said they were £1.34 down the road - "go there then" I was told. So I
got the slabs out and havent been back since.
Alan
--
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Stuart Noble
> While we're on the subject and I was searching for Cempolatex, I noticed:
>
> www.beersltd.co.uk
>
> which tells me Cempolatex 1 pack is 17.35 inc VAT.
>
According to the COSHH sheets, the one pack contains cement, and
the dry part of the two pack is 60% alpha quartz/30 % cement. I'll stick
with the idea that the 2 pack (sbr) is used where there's a danger of
damp, and the one part (or just a pva mortar) is fine for everything else.
Tim S
> Tim S wrote:
Good call Stuart.
I've followed that up. Makes it the same as the 2 part "Part A Powder". Odd
though: I can't get the data sheet for the "Part B" liquid for the 2
pack...
Also makes the name a bit of a con: "Cempolatex", if there is no "latex" in
it. I checked the COSHH sheet for the Arditex equivalent "2 part" and the
liquid is "High ammonia preserved natural rubber latex concentrate"
and "methanol".
I'm not sure if I should be saying "oh bugger" at this point :(((
Well I know what not to buy...
I suppose, given the applied stuff seems OK over all bar perhaps 2m2 of the
19m2 floor, that if push comes to shove, I might trim out the dodgey
patches and infill with some proper 2 part and stabilise the substrate with
SBR first.
The patches are small (worst is 1m x 30cm) and isolated, so it will be an
almost trivial job for me now I've got vaguely level edges to work too. I
need to get a few bags of compound anyway as I've to make good the bit by
the fireplace when I take the fire hearth out in April, and some of the
other floors need patching and smoothing. I'll just need another bag or
two, not a disaster...
Anyone want to tell me if the above is a bad idea?
Now where's me anglegrinder...
Cheers
Tim
Tim S
>
> Good call Stuart.
>
> I've followed that up. Makes it the same as the 2 part "Part A Powder".
> Odd though: I can't get the data sheet for the "Part B" liquid for the 2
> pack...
>
> Also makes the name a bit of a con: "Cempolatex", if there is no "latex"
> in it. I checked the COSHH sheet for the Arditex equivalent "2 part" and
> the liquid is "High ammonia preserved natural rubber latex concentrate"
> and "methanol".
>
> I'm not sure if I should be saying "oh bugger" at this point :(((
But hang on...
http://www.bostik.co.uk/diy/product/33
clearly states:
"Latex modified self-levelling sub-floor compound"
Something's talking round objects... Perhaps I shouldn't worry after all.
I'd have to admit, Arditex's website is a hell of a lot more informative
than Bostik's. Arditex say, of their 2 pack, that it's suitable with damp
crappy substrates. I'm sincerely hoping the same applies to Bostik's
stuff...
This is very confusing.
Cheers
Tim
John Rumm
> But hang on...
>
> http://www.bostik.co.uk/diy/product/33
>
> clearly states:
>
> "Latex modified self-levelling sub-floor compound"
>
> Something's talking round objects... Perhaps I shouldn't worry after all.
As I mentioned before - you can certainly get latex products that don't
have a separate latex liquid. The price seems to be in the right
ballpark for that sort of product.