[sm_jamieson]

I have to screed a concrete floor slab. Screed is going over concrete,
not over insulation. Screed depth was supposed to be 60 to 70mm, but
the slab ended up a bit thicker than intended, so in some areas, the
screed will be down to about 40mm thick.
Will a normal dry mix sharp sand / cement be OK at that thickness, or
should I add anything (like SBR etc.) Floor will be tiled.
I was going to use sand / cement in case I need to slightly slope
levels to match floors in two adjoining rooms.
Or should I consider any other type of screed ?
Cheers,
Simon.

[Tim Watts]

On 28/05/10 12:53, sm_jamieson wrote:
I have to screed a concrete floor slab. Screed is going over concrete,
not over insulation. Screed depth was supposed to be 60 to 70mm, but
the slab ended up a bit thicker than intended, so in some areas, the
screed will be down to about 40mm thick.
Will a normal dry mix sharp sand / cement be OK at that thickness, or
should I add anything (like SBR etc.) Floor will be tiled.
I was going to use sand / cement in case I need to slightly slope
levels to match floors in two adjoining rooms.
Or should I consider any other type of screed ?
Cheers,
Simon.

I would have though 40mm was OK, but it's getting near the limit.

Perhaps prime with a cement slurry as you go to achieve a decent bond
with the concrete?

SBR will be bombproof at that thickness (and less).

The main downside with SBR (apart from the expense) is it makes for
messier handling - you'll get covered in stickiness, your tools will and
it's a bugger to get off if it's not washed immediatedly (ie white
spirit and/or metal scourer).

On the upside, your screed will not fall off, ever, if you follow the 3
step method:

Wash down concrete with dilute SBR

Prime as you go with cement/SBR slurry

Use SBR modified screed.

The handling is also a little weirder - it plasticises the screed
immensely, so despite a very dry mix, watch out for minor (2mm) humps
forming behind the tamper as it backflows (I had this happen). If you
catch then the next day, they can be "planed" off if small by hand with
a metal paint hook scraper and a certain amount of swearing. Wait a week
and it's angle grinder time.

I wouldn't say it's much harder than normal screed if you are forwarned
- mine was a learning curve!

Google for Cememtone SBR datasheet (and/or other brands) - they give the
mixing and application regimes in some detail. If you can't find them,
email me (posting addy valid) and I'll email you my collection of PDFs.

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

[andrew]

Tim Watts wrote:

I have to screed a concrete floor slab. Screed is going over concrete,
not over insulation. Screed depth was supposed to be 60 to 70mm, but
the slab ended up a bit thicker than intended, so in some areas, the
screed will be down to about 40mm thick.
Will a normal dry mix sharp sand / cement be OK at that thickness, or
should I add anything (like SBR etc.) Floor will be tiled.
I was going to use sand / cement in case I need to slightly slope
levels to match floors in two adjoining rooms.
Or should I consider any other type of screed ?
Cheers,
Simon.

I would have though 40mm was OK, but it's getting near the limit.


With or without screed fibres?

I've recently had 65^2 of uneven concrete screeded and I know it must be
thin in places as I had 1m^3 left over. even where it tapers of by a door
it hasn't given a problem yet though I fully expect to have to make good
with some epoxy.One chap and a laser level laid the lot in a day without
expansion joints which surprised me a bit.

AJH

[Tim Watts]

On 28/05/10 21:21, andrew wrote:
Tim Watts wrote:

I have to screed a concrete floor slab. Screed is going over concrete,
not over insulation. Screed depth was supposed to be 60 to 70mm, but
the slab ended up a bit thicker than intended, so in some areas, the
screed will be down to about 40mm thick.
Will a normal dry mix sharp sand / cement be OK at that thickness, or
should I add anything (like SBR etc.) Floor will be tiled.
I was going to use sand / cement in case I need to slightly slope
levels to match floors in two adjoining rooms.
Or should I consider any other type of screed ?
Cheers,
Simon.

I would have though 40mm was OK, but it's getting near the limit.


With or without screed fibres?

Can't answer that for dry screed. However, I've done down to 15mm SBR
screed without fibres with no problems, on small areas (1m x 2m) and
25mm SBR screed over 3x3m areas. I think the SBR bonding is too great to
allow easy cracking.

I've recently had 65^2 of uneven concrete screeded and I know it must be
thin in places as I had 1m^3 left over. even where it tapers of by a door
it hasn't given a problem yet though I fully expect to have to make good
with some epoxy.One chap and a laser level laid the lot in a day without
expansion joints which surprised me a bit.

AJH


--
Tim Watts

Hung parliament? Rather have a hanged parliament.

[sm_jamieson]

On 28 May, 21:35, Tim Watts wrote:
On 28/05/10 21:21, andrew wrote:



Tim Watts wrote:

I have toscreeda concrete floor slab.Screedis going over concrete,
not over insulation.Screeddepth was supposed to be 60 to 70mm, but
the slab ended up a bit thicker than intended, so in some areas, the
screedwill be down to about 40mm thick.
Will a normal dry mix sharp sand / cement be OK at that thickness, or
should I add anything (likeSBRetc.) Floor will be tiled.
I was going to use sand / cement in case I need to slightly slope
levels to match floors in two adjoining rooms.
Or should I consider any other type ofscreed?
Cheers,
Simon.

I would have though 40mm was OK, but it's getting near the limit.

With or withoutscreedfibres?

Can't answer that for dryscreed. However, I've done down to 15mmSBRscreedwithout fibres with no problems, on small areas (1m x 2m) and
25mmSBRscreedover 3x3m areas. I think theSBRbonding is too great to
allow easy cracking.

I've recently had 65^2 of uneven concrete screeded and I know it must be
thin in places as I had 1m^3 left over. even where it tapers of by a door
it hasn't given a problem yet though I fully expect to have to make good
with some epoxy.One chap and a laser level laid the lot in a day without
expansion joints which surprised me a bit.


Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

[Tim Watts]

On 29/05/10 23:00, sm_jamieson wrote:

Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

Copy of data sheet sent to your hotmail address - if that's not valid,
please email me one that is

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

[sm_jamieson]

On 30 May, 09:32, Tim Watts wrote:
On 29/05/10 23:00, sm_jamieson wrote:

Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

Copy of data sheet sent to your hotmail address - if that's not valid,
please email me one that is

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

Thanks, got it.
Simon.

[sm_jamieson]

On 31 May, 11:38, sm_jamieson wrote:
On 30 May, 09:32, Tim Watts wrote:

On 29/05/10 23:00, sm_jamieson wrote:

Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

Copy of data sheet sent to your hotmail address - if that's not valid,
please email me one that is

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

Thanks, got it.
Simon.

So it looks like half water, half SBR.
How did you mix it ?
Looking at their website it seems like you need a special
forced action mixer.
Simon.

[Tim Watts]

On 31/05/10 12:16, sm_jamieson wrote:
On 31 May, 11:38, wrote:
On 30 May, 09:32, Tim wrote:

On 29/05/10 23:00, sm_jamieson wrote:

Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

Copy of data sheet sent to your hotmail address - if that's not valid,
please email me one that is

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

Thanks, got it.
Simon.

So it looks like half water, half SBR.

IIRC, that's the one...

How did you mix it ?
Looking at their website it seems like you need a special
forced action mixer.

Nah - normal mixer is fine. However, they do mention that air
inorporation may be a problem. So I mixed the ingredients dry, then
added the liquid (premixed SBR/water) and mixed for the minimum time to
get it right.

Fill the mixer with water as soon as you dump the load though, and leave
it turning, or you'll never get the SBR off.

Slurry I mixed with a spoon in a bowl and applied with a large
paintbrush as I went.

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

[sm_jamieson]

On 31 May, 13:06, Tim Watts wrote:
On 31/05/10 12:16, sm_jamieson wrote:



On 31 May, 11:38, *wrote:
On 30 May, 09:32, Tim *wrote:

On 29/05/10 23:00, sm_jamieson wrote:

Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

Copy of data sheet sent to your hotmail address - if that's not valid,
please email me one that is

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

Thanks, got it.
Simon.

So it looks like half water, half SBR.

IIRC, that's the one...

How did you mix it ?
Looking at their website it seems like you need a special
forced action mixer.

Nah - normal mixer is fine. However, they do mention that air
inorporation may be a problem. So I mixed the ingredients dry, then
added the liquid (premixed SBR/water) and mixed for the minimum time to
get it right.

Fill the mixer with water as soon as you dump the load though, and leave
it turning, or you'll never get the SBR off.

Slurry I mixed with a spoon in a bowl and applied with a large
paintbrush as I went.

--
What consistency should you aim for - dry as possible as for plain
sand/cement screed, or a little bit wetter ?

The other thing they mention is cleaning the concrete base first (they
say shot-blasting etc !!!). One area of base was poured last week, the
other is 2 years old. Did you prepare the base first ?
I could wash the lot with brick acid first I guess.

Also (sigh) I need to clean out my cement mixer. Its a bit encrusted
at the moment, and I'm sure you want it smooth and clean so the stuff
slides out happily !

Cheers,
Simon.

[Tim Watts]

On 31/05/10 13:21, sm_jamieson wrote:
On 31 May, 13:06, Tim wrote:
On 31/05/10 12:16, sm_jamieson wrote:



On 31 May, 11:38, wrote:
On 30 May, 09:32, Tim wrote:

On 29/05/10 23:00, sm_jamieson wrote:

Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

Copy of data sheet sent to your hotmail address - if that's not valid,
please email me one that is

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

Thanks, got it.
Simon.

So it looks like half water, half SBR.

IIRC, that's the one...

How did you mix it ?
Looking at their website it seems like you need a special
forced action mixer.

Nah - normal mixer is fine. However, they do mention that air
inorporation may be a problem. So I mixed the ingredients dry, then
added the liquid (premixed SBR/water) and mixed for the minimum time to
get it right.

Fill the mixer with water as soon as you dump the load though, and leave
it turning, or you'll never get the SBR off.

Slurry I mixed with a spoon in a bowl and applied with a large
paintbrush as I went.

--
What consistency should you aim for - dry as possible as for plain
sand/cement screed, or a little bit wetter ?

I had a labourer helping who'd done dry screeding before. We mixed
according to the data sheet, which to me seemed very dry and to him
seemed normal (so he said). However, it acted like it was wetter. Now,
I'd gone with a plan of screwing level battens to the wall and using a
2x4" taper bar with "ears" screwed on the ends at the top so that when
the ears rested on the wall battens, then the tamper would tamp to the
correct level. This turned out to be a good idea (though a bit alien to
my employee) as the screed acted wetter than it was (there are warnings
to this effect, if not in your data sheet, then one of the other
manufacturer's).

So if you are planning to screed the old fashioned way by running screed
round the edges of the room, then infilling, you might want to make it a
notch dryer than you think. OTOH, if you are going to splat it on and
screpe it level, then float it off (the sort of thing I'd do 'cos I
can't do screeding the proper way) then I think you'll find the mix OK
if done by the sheet. It trowells well with a steel float, and it
behaves quite well with tamping and scraping off (rather like a *very*
viscous plastic mass).

The other thing they mention is cleaning the concrete base first (they
say shot-blasting etc !!!). One area of base was poured last week, the
other is 2 years old. Did you prepare the base first ?
I could wash the lot with brick acid first I guess.


I didn't bother. Onto old concrete, I hoovered with a VAX to remove
excess dust and crap, then poured SBR/water in a 1:4 (that's on the
sheet) and brushed it in to saturation. That will bind up anything loose
in the surface. This can be left to dry as long as you like, or done the
day before. The cement/SBR slurry will need to be applied as you go so
it maintains a wet interface to the screed and that will bond the screed
to the concrete in a highly reliable way.

The only thing I would to is ensure you don't have large areas of
bitumen on the surface, should you have just peels tiles or wood parquet
off - even SBR doesn't like bitumen.

Also (sigh) I need to clean out my cement mixer. Its a bit encrusted
at the moment, and I'm sure you want it smooth and clean so the stuff
slides out happily !

Mine's not that clean. It was second hand, and I did take an SDS to it
to take of the thicker crap - but it is most certainly not gleaming
steel. Don't worry about that - the SBR screed will plop out OK. It's
leaving SBR screed in it that's the problem - you will not shift that
half as easily.

Beware of the ground you dump the mixer cleaning water on too - I
managed to make my lawn go like plastic afterwards. Raking out a small
ditch next to the mixer to contain the washings might be an idea if you
have a fine garden. Don't dump the washings on your block drive or it's
liable to go shiney. SBR is amazing stuff at not coming off.


Sounds like you'll need a fair quantity. You can get it in 25l cans for
about 70-80 quid all in. I got mine from here by internet:

http://www.permagard.co.uk/index.php...products_id=77

They were fast when I last ordered (3 days IIRC).

Cheers,
Simon.



Have white spirit and wire wool handy to clean anything metal like the
float - if it sets on your tools, white spirit works.

Can't remember who put me onto SBR, but it was here. I've been using it
for all manner of floor work since and in particular patching loose screed.

http://photos.dionic.net/v/public/bu..._0018.jpg.html

In that, the light grey areas are SBR screed patching to infill deep
damage. The brown is the original very weak screed - wasn't weak by the
time I'l poured some 4-5 gallons of SBR/water over it - twice!. The
patching screed was to save on the rather expensive StopGap 900 that was
going on top, and also to keep the Stopgap 900 within its limitation of
depth. The SBR screed was typically 10-20mm thick and feathered at the
edges, but testing with a chisle showed that it had bonded perfectly to
the crap underneath. Even teh concrete wasn't that strong. The floor is
now tiled with slate and is showing no signs of being unhappy.

I did the daughter's bedroom and the bathroom as a full rescreeding job
down to concrete - using SBR as the thickness was about 30mm and also as
an aid to holding back damp (we have a patchy DPM in this house - it's
old). In that respect it seems to work.

Good luck

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

[sm_jamieson]

On 31 May, 15:56, Tim Watts wrote:
On 31/05/10 13:21, sm_jamieson wrote:



On 31 May, 13:06, Tim *wrote:
On 31/05/10 12:16, sm_jamieson wrote:

On 31 May, 11:38, * *wrote:
On 30 May, 09:32, Tim * *wrote:

On 29/05/10 23:00, sm_jamieson wrote:

Whats the process and quantities to mix SBR screed then? I have a
belle mixer that needs a good clean out !
Simon.

Copy of data sheet sent to your hotmail address - if that's not valid,
please email me one that is

--
Tim Watts

Hung parliament? Rather have a hanged parliament.

Thanks, got it.
Simon.

So it looks like half water, half SBR.

IIRC, that's the one...

How did you mix it ?
Looking at their website it seems like you need a special
forced action mixer.

Nah - normal mixer is fine. However, they do mention that air
inorporation may be a problem. So I mixed the ingredients dry, then
added the liquid (premixed SBR/water) and mixed for the minimum time to
get it right.

Fill the mixer with water as soon as you dump the load though, and leave
it turning, or you'll never get the SBR off.

Slurry I mixed with a spoon in a bowl and applied with a large
paintbrush as I went.

--
What consistency should you aim for - dry as possible as for plain
sand/cement screed, or a little bit wetter ?

I had a labourer helping who'd done dry screeding before. We mixed
according to the data sheet, which to me seemed very dry and to him
seemed normal (so he said). However, it acted like it was wetter. Now,
I'd gone with a plan of screwing level battens to the wall and using a
2x4" taper bar with "ears" screwed on the ends at the top so that when
the ears rested on the wall battens, then the tamper would tamp to the
correct level. This turned out to be a good idea (though a bit alien to
my employee) as the screed acted wetter than it was (there are warnings
to this effect, if not in your data sheet, then one of the other
manufacturer's).

So if you are planning to screed the old fashioned way by running screed
round the edges of the room, then infilling, you might want to make it a
notch dryer than you think. OTOH, if you are going to splat it on and
screpe it level, then float it off (the sort of thing I'd do 'cos I
can't do screeding the proper way) then I think you'll find the mix OK
if done by the sheet. It trowells well with a steel float, and it
behaves quite well with tamping and scraping off (rather like a *very*
viscous plastic mass).

The other thing they mention is cleaning the concrete base first (they
say shot-blasting etc !!!). One area of base was poured last week, the
other is 2 years old. Did you prepare the base first ?
I could wash the lot with brick acid first I guess.

I didn't bother. Onto old concrete, I hoovered with a VAX to remove
excess dust and crap, then poured SBR/water in a 1:4 (that's on the
sheet) and brushed it in to saturation. That will bind up anything loose
in the surface. This can be left to dry as long as you like, or done the
day before. The cement/SBR slurry will need to be applied as you go so
it maintains a wet interface to the screed and that will bond the screed
to the concrete in a highly reliable way.

The only thing I would to is ensure you don't have large areas of
bitumen on the surface, should you have just peels tiles or wood parquet
off - even SBR doesn't like bitumen.

Also (sigh) I need to clean out my cement mixer. Its a bit encrusted
at the moment, and I'm sure you want it smooth and clean so the stuff
slides out happily !

Mine's not that clean. It was second hand, and I did take an SDS to it
to take of the thicker crap - but it is most certainly not gleaming
steel. Don't worry about that - the SBR screed will plop out OK. It's
leaving SBR screed in it that's the problem - you will not shift that
half as easily.

Beware of the ground you dump the mixer cleaning water on too - I
managed to make my lawn go like plastic afterwards. Raking out a small
ditch next to the mixer to contain the washings might be an idea if you
have a fine garden. Don't dump the washings on your block drive or it's
liable to go shiney. SBR is amazing stuff at not coming off.

Sounds like you'll need a fair quantity. You can get it in 25l cans for
about 70-80 quid all in. I got mine from here by internet:

http://www.permagard.co.uk/index.php...info&products_....

They were fast when I last ordered (3 days IIRC).

Cheers,
Simon.

Have white spirit and wire wool handy to clean anything metal like the
float - if it sets on your tools, white spirit works.

Can't remember who put me onto SBR, but it was here. I've been using it
for all manner of floor work since and in particular patching loose screed.

http://photos.dionic.net/v/public/bu..._0018.jpg.html

In that, the light grey areas are SBR screed patching to infill deep
damage. The brown is the original very weak screed - wasn't weak by the
time I'l poured some 4-5 gallons of SBR/water over it - twice!. The
patching screed was to save on the rather expensive StopGap 900 that was
going on top, and also to keep the Stopgap 900 within its limitation of
depth. The SBR screed was typically 10-20mm thick and feathered at the
edges, but testing with a chisle showed that it had bonded perfectly to
the crap underneath. Even teh concrete wasn't that strong. The floor is
now tiled with slate and is showing no signs of being unhappy.

I did the daughter's bedroom and the bathroom as a full rescreeding job
down to concrete - using SBR as the thickness was about 30mm and also as
an aid to holding back damp (we have a patchy DPM in this house - it's
old). In that respect it seems to work.

Good luck

Thanks, excellent information.
I think the SBR screed might be good at doing the floor in stages /
since it will all stick so well. Perfect for my needs.
I'll let you know how it goes - probably not doing it for a few weeks.
Simon.