At some point between now & summer I need to redo the back garden, currently it is completely slabbed with 3 x 2 slabs and badly done. I was looking at including a more decorative (slabbed) section maybe something circular or coloured but I cant really afford the cost to buy the finished product. Is it feasible and cost effective to make slabs something like 45 x 45 cm. I have the time to do a a few at a time if its possible or worthwhile.
You used to be able to buy moulds for making your own bricks and slabs from concrete, although that was back in the 1960s. However, my father made his own from wood. Just make sure you don't make the slabs too thin
- look at the commercial stuff for guidance.
Allow a slight taper on the sides, to aid with release. It is easier if you make the sides as a surround that can be removed separately from the top, but with a catch to keep them together until you are ready to separate them.
It is also a good idea to include a texture on the top surface - which is the bottom of the mould. There is quite a lot of scope for artistic effect here - perhaps making patterns with a router - but rough wood works well too.
You need a large flat area to turn the slabs out onto. ISTR the mix was fairly stiff. Place it into the mould and use a board to tamp it down and to level off what will become the underside. Then you turn the mould upside down, undo the catches and carefully lift the sides away, before removing the top. It helps removal if you have handles fitted to them.
Leave the slabs to set, then lay them as you would commercial products.
Colin Bignell
Yes its very doable.
A mistake new slabmakers often make is to fail to get the mould sufficiently accurately square. If its out by 2mm, its going to look wrong when laid.
If you want a smooth surface, thick polythene is the material of choice to line the mould.
Cavities in the slab are ever an issue. The standard way to avoid them is to use a vibrator of some sort. Its also possible to simply let cavities happen and fill the top surface ones with a dark mix afterwards.
Do an Ebay search under "paving slab mould". About 45 there, even if you do not use it may give a few ideas.
45x45cm is a common size in very cheap "contract" slabs. They can be brightened with the odd colour.
How long must I leave in the mould before turning them out to cure? I assume I would not need to use mtal reinfrocing bars?
If you need a lot, it might be more efficient to lay polythene sheet over a flat area, then place a grid of timbers of the right thickness on that. You would probably need to make halving joints where they cross, to keep them at the right spacings when you start to add concrete. Then fill the grid with concrete, tamp down with a board and finish with a stiff brush to give texture. You get less choice of surface pattern that way, but you could make quite a number of slabs in one go.
You assume correctly.
Colin Bignell
Thanks all useful tips.
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