Mortar mix help

Are you mixing in a cement mixer or wheelbarrow? 4 sand 1 cement is more than fine, dampen the backs of the slabs that you are about to lay first or prime them with SBR to control any suction and help them bond.

 

It's four to one, ie four shovels of sand to one shovel of cement, four buckets of sand to one bucket of cement, four spoons of...... you get the idea. It's more than enough cement, less would be ok. Mixing in a wheelbarrow, you have to make sure the mortar is mixed and turned over thoroughly. SBR is available from any builders merchants, it's a primer amongst many things and helps bond materials and surfaces together, you paint the backs of the slabs with it before laying.

 

4:1 is fine, as jord has explained you are using the right mix. Half a bag of cement is too much for four shovelfuls of sand

 

Is it a dry mix or wet mix, I’m not an expert but the more details the more people can help. I’ve laid my own slabs on both dry and wet mix and they took ok. As jord said wetting the underside of the slabs or priming them with a suitable primer might help.

 

I suspect u will need to take up unfortunately but wait for someone with more knowledge than me to confirm. I would guess that priming the backs like jord said will help with suction and stop it drying out to quickly and help them bed. Once they are down obviously don’t walk on or disturb them either

 

Lot of mixed advice on the ‘simple’ task of laying slabs and even if they should bond to mortar bed or not

Some say doesn’t matter as pointing will hold them firm and mortar bed is for levelling them

Personally, don’t agree with that but like you, I’m only diy so not laid hundreds of patios !!

Can’t see how it’s a good idea that only the edges of slabs are bonded once pointed as this doesn’t give much surface area - compared to the underside of slab

You don’t say what material the slabs are made from ?

If porcelain, 100% every time they must be primed with SBR slurry as porcelain isn’t so porous so the mortar can’t get a grip

Stone / cement slabs can be dusty, sandy and porous, so they either suck the water out the mortar before it cured or it simple doesn’t stick due to dust

The few I have laid, I’ve primed the backs, regardless of material with SBR Slurry

Can either buy this ready made, Priming Slurry, has an extended ‘pot life’ as has retarders added so convenient to use over days / hours

Or mix your own-
SBR at 1-4 water
Whisk in cement powder to form a thick, brushable slurry

Stir whilst using so cement doesn’t sink to bottom, keep out of sunlight and keep it as cool as possible, don’t use the next day so mix smallish batches

Paint on the backs of slabs (or use a heavy pile roller) and bed slab onto wet mortar bed, level, etc

Set up a ‘slurry station’ for painting away from laid slabs as you want to avoid splashing newly laid slabs

Work with a supply of clean water and rags and wipe up any slurry from face of slabs as you go

The loose slabs you have, can again try the slurry method to stick them down, but paint both mortar bed and slab, lay them back down then add some slabs on top to improve contact - leave for couple days - avoid rain

Also read up online and take a look at ‘The Paving Expert’

Excellent site that covers everything to do with groundworks, paving, etc. They’ve had a site revamp so now easy to navigate and find what you need

Anyway, give the SBR Slurry a try and let us know the results - good luck

 

Rocking and not bonding are different things.

None of the slabs round my place rock but none are bonded. Most are original (mid 70s) but many have been lifted and replaced for various reasons.

We did an awful lot of paving in the City of London back in the day, again no bonding.

You need a solid base then bed the slabs properly and not disturb them for a couple of days. Take the time to do a good job on the pointing.

 

Mix it as per the manufacturers instructions

 

If your mixing your own, then yes, Everbuild products seem well regarded in reviews, including SBR

As above, follow M I printed on the label for each specific task as like many products, these have several uses and the ratios may well differ, depending on use

From memory, it’s 1 part SBR to 4 parts water, mix together, then add in cement powder to form a brushable, thickish slurry and stir well to break up the powder as it clumps together

Keep a stick in the mix so you can stir regularly, either brush on or use a paint roller (I may have mentioned this above)

Can also buy ready made ‘paving primer/slurry’ , some powder form or others as a thick paste that you add water to

Goggle ‘Paving Primer’ for more info (or mix your own)

As to best implement for measuring - well …… depends on what you have to hand and the quantity your looking at mixing

Simple ‘recipe’ @ 1 SBR to 4 water (but do check this on the label)

So as long as you use the same receptacle for both the SBR and the Water, it doesn’t matter what you use as it’s just a simple ratio - 1 teaspoon SBR + 4 teaspoons water

1 jug SBR + 4 jugs water …… etc

As for the cement, just eyeball it to reach the desired consistency - I don’t think the above needs to be super critically accurate to the gram or millimetre ….. you ain’t baking a cake here mate

One last thing - whatever you mix the slurry in, make sure your happy to either dump it afterwards or keep for similiar tasks as you won’t be cleaning it out. A simple bucket / empty 10lt paint pot is all you need for this