floor screed mix?

[browfish]

I am about to screed my floor in my extension have now got the roof and windows in so its weatherproof. My question is what should this mix consist of. ITs is about 50mm thick and will be layed on the conrete slab with a heating cable on the bottom.
thanks

 

[noseall]

usually, a mix of 3 parts screed sand (grit sand) to 1 cement will be ok.
some add fibres to the mix to help prevent cracking, others lay thin re inforcing mesh in the screed thickness.
the mix needs just enough water added to it, to hold it together when squeezed in your hand. too much water, and you end up with the surface "dusting". too little and it wont bind.

 

[browfish]

Thanks alot
What exactly is screed sand (grit sand). Not heard of that before. Is grit sand the same as sharp sand?

Also, where i am knocking a wall down between the original house and the extension, how do i bridge the caviy in the wall. The floor in the original part of the house is suspended timber (some of it) by the way.

 

[masona]

Thanks alot
What exactly is screed sand (grit sand). Not heard of that before. Is grit sand the same as sharp sand?

Not heard of grit sand before

I believe Sharp Sand got the name as it feel sharp when you put your hand in it

 

[noseall]

up here in staffs we call the sand with which you lay floors either concrete sand, screed sand or grit sand. all exactly the same.
darn sarf i think they call it sharp sand.
its very coarse almost like pulverized gravel .
mixed with salt they lay it on roads in the winter.


take the masonry down to the bottom of the joists .
nail a shutter board along the joist ends to full depth of the joists.
lay some 1200gauge polythene in the trough.
fill with floor screed mix and trowel up with rest of the floor.

 

[browfish]

Excellent. THanks
So just to clarify, 3 parts sharp sand (aka grit sand to you northerners), 1 part cement.
cheers

 

[noseall]

yep.

p.s. i'm a midlander not a northener.

 

[scaff]

usually, a mix of 3 parts screed sand (grit sand) to 1 cement will be ok.
some add fibres to the mix to help prevent cracking, others lay thin re inforcing mesh in the screed thickness.
the mix needs just enough water added to it, to hold it together when squeezed in your hand. too much water, and you end up with the surface "dusting". too little and it wont bind.

Hello, I used a 4:1 mix and everything seemed to go alright, but I have got some patches which did not bind properly, is there something I can add now to 'seal' it ? I do need to lay some leveling as it is slightly lower than anticipated ( was a screed virgin till last week )

Cheers

 

[Maverick81]

Im looking at levelling the concrete floor in my workshop. Never done anything of this sort before. Ive been looking at a self-levelling compound which i understand you just mix and throw down and it levels itself out.
But what is this word "screed" i keep coming across. Never heard this word before. What is "screed" please?

 

[dann09]

OP:
The slab must be well dry before you lay any screed - bone dry is best, but not always possible with modern pours "tanked" in a membrane.

If you are satisfied with the slab, first mix a slurry of sand and cement, or something like SBR, and "wash" the conc surface with it, and when it goes tacky then lay the screed.

Leave very small gaps at the edge of the screed, it can, depending on conditions, occasionally expand a few mm.

Not a criticism, but if you dont know the mix, are you comfortable laying a screed containing UFH? It can sometimes be a tricky business laying either of them.

 

[Watshot]

Seven years ago Dann, good or bad he's probably finished by now.