Floor screed advise please

[loudog]

Hi ya all, My game is block paving and tarmac but build the odd wall and lay foundations. I built a concrete floor which he has built the block work on but he wants me to come back and do the floor screed for him. It is not a big area about 4mts x4mts, any advise would be really good. I am familiar with screed rails and know the mix has to be dryish, do I need to add any liquids to the mix?

Kind regards chaps

[lutonlagerlout]

grit sand/ cement 3:1 +100 ml of pva and a handful of fibres
set your screed rails up to the levels then infill and screed off
if you arent really a a screeder (like me) go back the next day and remove the rails and infill the voids
in a normal mixer about a 1 /5 bucket of clean water
cheers LLL

[loudog]

Thanks LLL, my friend has put me off as he said it is a skilled job, but been paving for good 10years and can concrete, have a good understanding of screeding. Do i need to wet the existing concrete floor as not to draw the cement out of the floor screed.
Thanks

[lutonlagerlout]

sorry mate,yes you need to prime the floor with a pva and water mix
its by no means hard,you will just be slower than pro screeders
the gear mustn't be too wet
LLL

[henpecked]

I'd say screeding is more forgiving then concrete finishing TBH

[rab1]

the mix has to be dry as in when squashed in your hand forms a ball but your hands are still dry.

[macgrl]

Hello all,

I too am laying some screed. I have no experience of this but the area is quite small and will be under a bath. I took the old one out to find that the floor level is about 40mm lower than the rest of the bathroom floor.

Its is the contrete house base layer below it. The area is the size of a regular bath so not very big and won't be seen.

So basically do I mix 3:1 grit sand to cement with 100ml of pva to a dry mix that can be compressed in my hands. I shouldn't have a problem getting it level with rails etc.

Do I have to add fibres or doesn't it matter as it is under the bath and won't have any foot traffic on it?

I will need to seal the contrete floor with a pva / water mix - what ratios.

Thank you very much.

macgrl

[lutonlagerlout]

it should tell you on the PVA/SBR the ratio for priming
for me half a bucket of water and maybe 250ml works ok

just take your time and keep it moist rather than wet
LLL

[macgrl]

Thank you very much lutonlager lout.

Two other quick questions -

do i really need fibres? - I can't seem to find them anywhere to buy. are they really that important considering the job I am doing.

Also I have had a look around and would a 3:1 mix be too strong? could i use 4/5:1

Thanks so much. Very much appreciated.

macgrl

[Pablo]

No you don't need fibre and 5:1 will be fine.

[macgrl]

Thank you very Much pablo

[lutonlagerlout]

all floor screed should be 3:1
LLL

[Brucieboy]

LLL, have to disagree. We supply 1000's of cubic metres of ready mixed floor screed every year, the vast majority of which is 4:1. Fibrescreed is increasing in popularity, mainly for use with underfloor heating systems. We are rarely asked for 3:1 - it's too rich!! All our screed is mixed in forced action mixers.

Macgrl - be careful to ensure the screed is fully dry before applying resilient floor coverings such as vinyl, particulary the very expensive stuff such as Amtico. The rule of thumb is 1 day per 1mm thickness but considerably longer if the screed is placed directly onto a concrete slab without a separating membrane between. Failure to do so could result in the vinyl bubbling and lifting due to vapour pressure. Other finishings such as carpet are not so critical.

[lutonlagerlout]

have you got a link or reference for that brucie?
not doubting you ,but I have always been told to knock up floor screed at 3:1
the more cement the harder it is to screed but IME a far better job
the guys i use with the putzmeister use around 8 bags of cement to 1 tonne of grit sand,however this sand has an inherent moisture content,so maybe that is more like 4:1 too
LLL

[lutonlagerlout]

found this on cemex site

Product reference: Readyscreed Original

Mix:
1:3 - For minimum strength of 25N/mm2 after 3 days and 30N/mm2 after 28 days
1:4 - For minimum strength of 20N/mm2 after 3 days and 20N/mm2 after 28 days

LLL