Laying slabs, do I need a cement mixer or not?

aliasojo

We have always laid slabs on a bed of sand with some dry concrete lightly mixed in on top. It was someone who lays pathways etc for a living who showed us what to do and we've always just stuck with this method.

Problem is, it can be difficult getting the height right, if the bed is too high you can only tamp the slab down so much before having to lift it and adjust the levels and if it's too low you have the same problem and need to lift it again.

We've got heavy utility slabs to lay and I thought it might be easier to lay them on a wet concrete mix of some kind, that way they would adjust more easily and wouldn't need lifted, they could be levelled with less hassle.

I needed to hire a whacker plate anyway, and the mixer was only a fiver extra as part of a special deal pack so I got it too. I'm now wondering if I should stick to the dry sand/cement mix and dont need the mixer after all.

I'm really not sure what to do for the best?

wallbash

http://www.wickes.co.uk/slablayer/invt/153707/

Take as long as you like to get the 'bed' level . Wet.. watering can . Gently lay slab on top.
Easy to get level , looks a little expensive , but you will have no waste and no hire charge.

aliasojo

Already hired the tools and bought the ton bag of sand.

ormus

ive laid many patios on just sharp sand or on plain (solid) earth.
with light foot traffic, not one of em has ever moved to any degree.

ive never used cement, mortar nor concrete.

wallbash

I'm now wondering if I should stick to the dry sand/cement mix and dont need the mixer after all.

Even if you don't add water , makes mixing easier.

Tucker

I've always used a wet mix, blobbed each corner and then tapped down.

More stable and faster.

Our driveway is laid on sand and it's a right mess with uneven flags, sand gets washed about underneath and moves all the time.

When I get round to lifting it, it will go on a wet mix ontop of whackered MOT.

If ou have the mixer, you may as well use it!

bobhawke

Blob of mortar in each corner is about the worst thing you could do for laying slabs, it leaves them really weak where there is no mortar, leaves gaps for rodents to get in to and leaves space for water to get in to and freeze.

They are heavy slabs so no need to lay them on a wet mix.
If they are plain grey council slabs then you can lay them on sharp sand but since you have a mixer you're best running some cement through it to stiffen it up, go for 10:1 it will be hard enough and it will save you money over something like 6:1.

27col

My back path is made from 3ftx2ft ex-council slabs. They are very heavy. What I did was to fix a couple of battens along where the edge of the slabs were going to be and then levelled the sand/grit using a straight piece of board. Then we lifted the slabs into place with some lengths of old seat belt from a scrap yard. When the slabs were laid down on the pre-prepared bed, we just slid the seat belt out from underneath. They have never moved in over 20 years. However, as someone has already said, the edges do need to be contained to stop any migration of the bedding sand from below. However, this is achieved by the levelling battens, or if you want, you can use a wet mix just to contain the edge

aliasojo

Just spent the afternoon levelling the ground. Not the easiest job in the world. The whacker plate helps though, it's easier to see the levels when the earth is compacted.

Good idea about the seat belt straps 27col. We have an old ratchet strap which is very long and the ratchet part is broken so I'm thinking we could utilise that to the same effect.

27col

Actually, I got the idea for the seat belts when I was watching a couple of contractors laying slabs. They used a couple of lengths of rope which achieved the same thing. I thought that the seat belts would disturb the sand much less and I was right.

plumb1_2

Lay them on a solid base of 6 sharp sand to 1 cement dry mix. The dampness in the ground and sand will be enough to set the mix.