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Posted: Wed Jun 14, 2006 6:58 pm
by irose
Hi
Love your existing calculators but I'm about to lay slabs on a MOT base and have been told to use 25mm thick mortar mix. Any ideas of how much sand and cement would be needed for an area of 23 sq m.
Thanks in advance
Ian
Posted: Thu Jun 15, 2006 6:34 pm
by K-TEK
I always use 50mm mortar bed which works out 1 ton per 10m2 ! Find thats a good rule of thumb (wot ever that means lol ) hope I`ve helped 
Posted: Fri Jun 16, 2006 7:50 pm
by irose
Thanks for the reply. Yep, helps a lot. Cheers.
Posted: Sun Jun 18, 2006 10:02 pm
by Tony McC
Use the calculator to determine how much bedding is needed at 50mm depth, and then just halve it! 
Posted: Mon Jun 19, 2006 3:27 pm
by bobhughes
Just so you know...
The expression rule of thumb has been recorded since 1692 and probably wasn’t new then. It meant then what it means now—some method or procedure that comes from practice or experience, without any formal basis.
It is likely that it comes from the ancient use of bits of the body to make measurements. There were once many of these: the unit of the foot comes from pacing out dimensions; the distance from the tip of the nose to the outstretched fingers is about one yard; horse heights are still measured in hands (the width of the palm and closed thumb, now fixed at four inches); and so on. There was an old tailors’ axiom that “twice around the thumb is once around the wrist�, which turns up in Gulliver’s Travels. It’s most likely that the saying comes from the length of the first joint of the thumb, which is about an inch.
You can find out anything on the interweb...
Bob
Posted: Mon Jun 19, 2006 9:22 pm
by Tony McC
I was always told that the width of the thumb is one-twelvth that of the foot, and is therefore an "inch". Fingertip-to-elbow was a 'Cubit' (as used by Noah and Sons, shipwrights and survival specialists), and there was summat about the ratio of head-to-hip:total height, but I can't recall what that was.