Screeded concrete bed

[Al Jardin]

Hello
Assuming I use slabs of a calibrated thickness would a screeded concrete bed be a workable method? I guess I'd have to use a fairly stiff mix with tollerance to tap down to FL a bit and, of coarse, sbr in it also. Opinions for and against.

Cheers.
Al

[r896neo]

Actually screeding it would be a problem i think. If it was wet enough to tamp level you obviously couldn't lwalk and therefore lay on it but if it was dry enough to lay on you would have to level it like a screeded floor which even with 10mm stones would be a ball ache. Also it would be difficult to ensure even compaction unless you consolidate it first which would make it even harder to screed.

This is spoken however by someone who has never done it so i may be missing some obvious work arounds?

[local patios and driveway]

Yep its very possible infact its a method i prefer over any.

Mix up a dry mix wet enough to make a snow ball that when thown 5ft above you lands the same way it went up, ie not fall apart in the air.

Screed it out then mix up a slurry, usualy 50-50 cement and water, add a dollop of sbr and pour on to the screeded bed, place stone on the slurry. Tap a little. Try and lift the stone the next day... The stone will break before it pulls up.
Fast and simple.

This is also a brilliant way to lay edges for block pavers, or when setting pavers on a step rather than using a mortar.

[Al Jardin]

Good point Neo but I'll work in small sections so as to keep off.
Lpad - to take it a step further would it be wise to add a bit of plasticiser to maintain stiffness but allow tapping dow say 5mm to Fl. Do you use ballast or sharp sand for your screed?

Al

[Carberry]

Good point Neo but I'll work in small sections so as to keep off.
Lpad - to take it a step further would it be wise to add a bit of plasticiser to maintain stiffness but allow tapping dow say 5mm to Fl. Do you use ballast or sharp sand for your screed?

Al

I use sharp sand, no need for plasticiser as well as SBR.

[local patios and driveway]

Yep sharp for me, never found the need for plasticiser unless doing brickwork.

[r896neo]

LPAD/ carberry what type of paving do you use this method for and i assume you walk on the screeded bed to lay?

If you had time i'd really appreciate a brief outline of the method. How do you find the actual screeding with stone in the mix?

Cheers

[local patios and driveway]

Neo, apart from actually showing you, theres not much more i can add to the description mate. Have a play

[r896neo]

Fair enough, do you tamp it as you go like screeding a floor and do you do large areas like that?

Cheers, will have a play.

[lutonlagerlout]

screeded beds work of with pressed or moulded flags
I have used the technique on council slabs
i cover the whole area to be slabbed with 4:1 screed
then wack,this is important
screed to levels,then carefully place slabs onto screed
if you start tapping you will cause problems
if your screed is spotty dog and it has been wacked no problem
LLL

[local patios and driveway]

I tend to screed areas with my level, tamp down with a float, screed again, then slurry.

[Al Jardin]

Here's a question. What if you needed a bit of give to tollerate variations in thickness of a slab. Could you not use a ballast type screed that had a low slump but had a bit of fat on the surface after tamping to aid adhesion. Lets say I use calibrated natural stone pre wetted or with sbr? Or just pill my finger out and experiment.

Al

[Carberry]

I don't understand why you would want to put ballast or hardcore etc in the mix. Are you planning on driving a fluly laden forklift over your patio?

[Al Jardin]

I don't understand why you would want to put ballast or hardcore etc in the mix. Are you planning on driving a fluly laden forklift over your patio?

Carberry
I'm painfully slow at paving so I want to find a quicker method. Only needs to be 50mm of bed on 100mm of type1. Mind you a good sharp sand mix with plasticiser in has plenty of give in it.

Al

[r896neo]

screeded beds work of with pressed or moulded flags
I have used the technique on council slabs
i cover the whole area to be slabbed with 4:1 screed
then wack,this is important
screed to levels,then carefully place slabs onto screed
if you start tapping you will cause problems
if your screed is spotty dog and it has been wacked no problem

I have used a normal screeded mortar bed for calibrated flags before but not concrete hence my queries. Wacking it and then screeding it seem like it would just tear all the stone with it requiring a lot of work to sort it out. I suppose i'll have to give it a try