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I've dug out about 10m2 and 4" deep of soil ready for some paving. The slabs are quite heavy duty ones. I'm not sure what to put on top of the soil before mixing the mortar to lay the slabs.
One neighbour has suggested I just lay the slabs on top of a bed of sharp sand without any mortar and pointing them is optional (surely thats not possible), another has said I can use some gravel/ stones from the garden.
The proper way is to get some hardcore and compact it down onto the soil, then lay the slabs on a bed of mortar. But can I get away with any of my neighbours suggestions? I can't find hardcore in a smaller quantity than a 800kg bag which is way too much. The paving will only be for light use eg. walking, tables etc. The soil base, after walking on it, feels pretty solid.
Sharp sand - find if slabs are on a slope the sand will wash away from under them.
For best results and a lasting job you need to have a firm well consolidated foundation if not the flags will move over time, if the ground is undisturbed and well compacted and the flags are not heavy duty you may get away without hardcore, I mix grit sand with a percentage of cement 1 good spade full to about a barrow of sand is enough and lay the flags onto this dry base the base must be flat and well compacted you really need a vibrating plate for this. make sure that you have a slight gradient and if next to property ensure that the gradient is away from the house to take water away. Over a short period natural moisture will cure the mortar and it will set like concrete. with this method you can control the levelling better than if placing on a cement mortar bed. What you must not do is lay the flags on dabs of mortar.
A lot depends on what your soil is like. If it's heavy, rock hard when dry and clumpy when wet, then you can get away with laying the slabs loose on a bed of sand, providing you bed them down well.
I've done this myself, with no problems, but only on areas that are used rarely, or as a base for sheds etc.
If your soil is crumbly and easy to work, then you need to do something more substantial.
i would go for laying on sand the way to get a solid finish is - to compress the base as much as possable , the sand base should be layed on 4 " base of crushed brick or MOT limestone chippings.
putting on morter pads ,risks the water collecting underneth and freezing ,pushing slabs up , a smaller builers merchant will deliver smaller amounts , half a ton is not unusual , do it rite , do it once
using 6 parts sand to one of cement. Lay this directly onto the ground (which must be well compacted) to a depth of around 50mm, and use a timber batten to get the sand/cement mixture reasonably level. Work as you go - don't try to lay the entire base first. The trick is to get the mixture right - it should just hold together if you squeeze a handful, but shouldn't feel wet and sticky.
Then lay your slabs directly onto the mixture and tap them level and flat, using a spirit level as you go, and don't walk on the slabs you've already laid. Leave a 10mm gap between the edges of the stones.
When you've finished, leave the area alone for at least 24 hours - 48 is better, and then make a completely dry mix of sand and cement. Throw this onto the paved area and use a soft broom to brush it into the gaps. Sweep all traces of the mixture off the slab faces as you go; it's worth taking your time over this.
Now leave the atmosphere and the weather to do the rest. The mixture in the gaps will harden as it takes up moisture from the air and from the next rainfall, and you'll have a nice neat, long-lasting job. Don't skimp on the depth of the bedding mix - it must be at least 50mm.
Thanks everyone - some very useful advice given here. I'll make sure the ground is well compacted and the bedding is sufficient. If I manage to do a good job of it I will take a photo and post it here for all to see, thanks.
on this subject than to take the advice given on the pages of;
It really is superb; Good information, well put together, and easy to read.
(ps I have no involvement with the site, other than as someone who has benefitted from it!)
Simsy. Thanks for that link - brilliant!
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