As mentioned earlier I have 50sqm of paving to lay and was planning to use standard 40 x 40 x 4 cm flags. The cost worked out at over €1000 for all the slabs. I have layed the aggregate base and was planning to lay the slabs on a dry mixture of sand and cement (6 parts sand: 1 part cement). I was also planning to lay the slabs adjacent to each other ie no buttering, no space, then point the joints with another dry mix of 3 parts sand: 1 part cement. Let me know if you think this is ok.
My problem now is that I have been offered slabs 40 x 40 x 28 cm for less than €400. The are from a reputable source. I wonder is the depth of these slabs ok. The patio is for pedestrian traffic only. Should I go for the cheaper slabs and do I have to vary the depth of aggregate and/or dry cement:sand on the upper course?
Depth of paving slabs
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Rich H
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- Location: Reading
There's nothing wrong with the slab thickness but you'll need to take a bit more care to ensure that the bedding course is fully in contact with the slabs as you lay them. What kind are they? 400x400 is not the most common of sizes.
My main concern is your comments about pointing. You might consider reading the main site on this topic. If you butt the slabs together you can't use a mix - your only options are either nothing or kiln dried sand.
My main concern is your comments about pointing. You might consider reading the main site on this topic. If you butt the slabs together you can't use a mix - your only options are either nothing or kiln dried sand.
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Tony McC
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400x400 is one of the popular continental sizes. It is actually a recognised BS size (Plan size F) but is less commonly used more decorative patio paving because we tend to use flags based around a 140 or 150mm module, neither of which suit a 400x400 flag.
28mm thickness would be a worry on a commercial project but for a private patio, there's no real problem.
As for the jointing, flags should never be laid in direct contact with their neighbours. This is termed butt-jointing and although it is done, it's naughty, and there should always be a joint of at least 2-5mm between adjacent paving units. This can be filled with jointing sand or one of the specialist narrow joint polymerics. Alternatively, go for a 12 ±3mm joint pointed with either a cement or a resin mortar.
28mm thickness would be a worry on a commercial project but for a private patio, there's no real problem.
As for the jointing, flags should never be laid in direct contact with their neighbours. This is termed butt-jointing and although it is done, it's naughty, and there should always be a joint of at least 2-5mm between adjacent paving units. This can be filled with jointing sand or one of the specialist narrow joint polymerics. Alternatively, go for a 12 ±3mm joint pointed with either a cement or a resin mortar.
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