Laying paving slabs on sharp sand and mortar mix

[markyyyyyy]

Hi,

I have 3 bags of mortar mix in the shed and am getting some sharp sand tomorrow, to lay my paving slabs.

Is it okay to lay the patio (450mm x 450mm slabs) on the mixture of sharp sand and mortar? Do I use a 5 parts sharp sand to 1 part mortar mixture?

If so, do I mix it as it is (dry mix), level the area off, and water the area prior to laying the slabs?

Cheers[/img]

 

[noseall]

What is 'mortar mix'?

I can only assume that it is some dry pre-mixed sand/cement stuff that you just add water too, yes?

Leave it where it is and go buy yourself a bag or two of cement to add to your sharp sand.

Yes, you can lay slabs on a dry bed and brush in some dry joint filling afterwards. However it won't last long.

Wet mix, solid bedded with a joint formed from the bedding is the 'quality' way to do it.

 

[markyyyyyy]

Thanks for the help.

So, do I mix the cement and sharp sand as it comes (dry), then level off the area to be paved? Once it's level, do I soak it with water prior to laying slabs?

Cheers.

 

[xdave]

Use a normal wet mix if you want it to last.

Grab yourself some cement and a cheap float to spread it out (you can make one with a bit of board with a block screwed on the back). Either buy cement with a plasticiser mixed in or get a small amount of that too to help when bedding the slabs in.

If your sub-base is level and has the correct fall then easiest way is to cut a couple of boards to the height required, screed in between them with another board and then lay the slabs out from one corner and then infill as you go along. If the slabs are not all exactly 450mm square (e.g. riven edges) then dry lay them all out first so you can adjust the spacing. It is much easier to do that when you can still walk around on them, and you can then lift each row at a time to pour the mortar down and use the following row to gauge the depth. Level each slab as you go along - don't leave it till you've done the next one or you may find it has settled and won't budge.

As noseall says if you can get the right amount of bedding mortar into the joints with each slab that is a good way of jointing them, but if you stop the base drying out too quickly you will have a couple of days to come back and point the gaps up before it cures and get a strong joint as well. I find it looks better with building sand mortar for the joints as you can get a nicer finish when pointing them off. I also find it harder to use the bedding mortar at the same time as laying as it tends to be sticker and is much easier to foul the faces. If your pre-mixed mortar is still good (I'm unsure if you 'found' it in your shed or if you bought it recently) then I'd point up with that after a day or so. If you decide on that route then go over all the joints when the bedding has cured enough to walk on but is still green and rake out any joints where you don't have at least 10mm clear gap to joint as you don't want it too thin unless you like redoing it every year after the frost breaks it out. Make sure all organic matter like flower heads, seeds, etc., are cleaned out else they will decompose, leave voids, fill with water and then blow with the frosts.

 

[theprinceofdarkness]

if you use a proper "plasticised" mortar mix, you can get the last millimeter right by thumping the slab. if you use a dry mix, you have to lift the slab and remove some of the powder. Don't go overboard with the pointing, depending on the gap, fill it with dry mix or pea gravel to within 1/4" of the top and just use a bit of mortar on top. Its just there to make it look good, unless gravity changes the slabs don't move sidewards!!!
Frank

 

[themiddleagedun]

"pea gravel"

 

[markyyyyyy]

Thanks for the help everyone.

I've gone for the option of mixing sharp sand with cement.

Having never done this before, this is what I plan to do - please correct if I'm missing anything or doing it wrong:

1. Sub layer of dirt + rubble - levelled off
2. Mix 10 bags sharp sand with 2 bag cement (dry - as it comes in the bags) and dump on top of sub layer, levelling it off
3. Before laying the slabs, spray water over the surface
4. Lay slabs, and fill in joint with dry mix

Thanks

 

[noseall]

1. Sub layer of dirt + rubble - levelled off

So far so good. May need compacting.

2. Mix 10 bags sharp sand with 2 bag cement (dry - as it comes in the bags) and dump on top of sub layer, levelling it off

Add water to it and leave it in the barrow.
The gear needs to be wet but not sloppy. Add enough water to make the gear 'workable'.

3. Before laying the slabs, spray water over the surface

No need for water. Shovel enough (wet)gear down to lay one slab. Set it level one way then add a fall the other i.e. 1:100. Then continue either laying the remaining slabs to this first one using a level or a line.

4. Lay slabs, and fill in joint with dry mix

NO! What is it with this dry mix bollax. Form a joint with the bedding mix and you can not go wrong. Then hit it with a pointing trowel or jointing iron, later on. If you get the mix right and solid bed you will be able to walk on the slabs after lunch.

 

[loply]

NO! What is it with this dry mix bollax. Form a joint with the bedding mix and you can not go wrong. Then hit it with a pointing trowel or jointing iron, later on. If you get the mix right and solid bed you will be able to walk on the slabs after lunch.

How do you go about getting the bedding mix into the gaps between the slabs to a consistent depth? What sort of gap are you talking about between slabs?

Not done much of this myself but when I have the gaps are usually tiny and I can't imagine how to get a wet mix of any kind set into them.

 

[noseall]

How do you go about getting the bedding mix into the gaps between the slabs to a consistent depth? What sort of gap are you talking about between slabs?

You chuck enough gear down to lay your first slab.

You trowel it about so that you have enough down to set it at the correct height relative to whatever.

You place your slab on your muck and rubber hammer it level one way or to falls the other. Make sure there is enough muck present so that you have plenty of 'knockage', meaning the whole base of the slab is in contact with the muck. No air spots.

You then put another load of muck down for the next slab then tease up a joint along side the first slab, formed from the bedding mortar.

You then lay the next slab butting it against the joint ensuring that you have some joint squeeze-out.

You then jump on the slabs after a few hours and point them. It's a bit like bricklaying. You end up with a solid hard wearing nicely pointed finish. Unlike the brush-in pointed knobs who lay them on spots or dry sand.
Totally useless.

Gauging the joints is a skill. You do have some wriggle time but you have to establish a joint pattern early on especially with Indian stone sizes.

You will often find with Indian stone that say three smaller units that are meant to equate to one bigger unit, often do not. They more often end up bigger, even without any joints. This means that you have to allow for slightly bigger joints around the larger units and keep the smaller units reasonably tight.

 

[geraldthehamster]

You then jump on the slabs after a few hours

Just to clarify, this is a metaphor, right?

Just in case the OP is tempted actually to jump on the slabs.



Cheers
Richard

 

[WabbitPoo]

if you use a proper "plasticised" mortar mix, you can get the last millimeter right by thumping the slab. if you use a dry mix, you have to lift the slab and remove some of the powder. Don't go overboard with the pointing, depending on the gap, fill it with dry mix or pea gravel to within 1/4" of the top and just use a bit of mortar on top. Its just there to make it look good, unless gravity changes the slabs don't move sidewards!!!
Frank

What a load of poo advice.

No offence....

 

[noseall]

You then jump on the slabs after a few hours

Just to clarify, this is a metaphor, right?

Quite so, yes.

In the winter time you would gingerly get on the slabs rather than leap about on them. Well pointed out.

 

[geraldthehamster]

What a load of poo advice.

No offence....

+1

Cheers
Richard