Iain Robinson wrote:
:: I posted here earlier in the week and some kind souls pointed me in the
:: right direction, clarifying what I should lay my patio on. But I need a
:: bit more clarification please.
::
:: After whacking down my sub-base I am putting down a drymix mortar to lay
:: the slabs onto. It seems one part cement to four parts sand is the right
:: ratio - correct? I had read that the sand for patio work should be sharp
:: sand (as it 'locks' in place) but I see that pavingexpert.com recommends
:: that soft sand be used for mixing up mortar. Which is correct? If it
:: should be soft sand what would the result of using sharp sand be? I have
:: already ordered the (sharp) sand. I went through what we wanted to do
:: with someone at the builders merchant and he seemed to agree that we
:: were on the right track, so hopefully this is not our first stumbling
:: block.
::

There's little difference in using soft or sharp sand in this instance, and
4:1 is a very strong mix for laying slabs on, I'd suggest 10:1 - you aren't
sticking them to anything, merely providing a semi-hard base, note the use
of the word 'semi' - you want water to be able to drain through - any pooled
water underneath or around the flags will cause all manner of problems when
it freezes, this is one of the reasons for good drainage....they used to
just lay them on sand and many firms still do, especially for patios and
paths, cement sometimes gets used under driveways, but even these are often
done on a bed of sand.
Another point; you say 'drymix'? - you aren't mixing it in the conventional
way? - IE with a mixer or by hand? - none of this is needed, all you need to
do is rake your sand level, throw on a sprinkling of cement and rake it into
the bed, about 2KG of cement per metre, meaning you will get 12M out of one
bag of cement and this is strong enough to run cars on.


:: I was also recommended to put down extra cement at the sides of the
:: patio to keep the sand in - should this be pure cement (put down dry, as
:: the mortar?) or just a mortar mix with a higher ratio of cement in (if
:: so what ratio).
::

Don't use pure cement as it's hideous when dried, a mixture of around 4:1,
but mixed in the conventional way, (with a drop of fairy liquid [1] for
plasticising) is more than adequate, you can do this the day after your
flags are all down, just go around the edges with a bucket of mortar and a
trowel, not forgetting to leave the surface below that of the flags, so that
you can fill in with bark or chippings if you want, the only problems I can
forsee doing it this way is that it may hold the water if you do it
completely, to counteract this, go along it with a garden fork and puncture
a few holes through after you have finished and prior to dressing with
stones/bark.

:: Apologies for the dumb questions but this is all new to me. I have this
:: week off work this week to do this - I want to be sitting on the patio
:: having a beer by Friday. In any spare moments during the process I also
:: have to decorate the kitchen........

Mmmm...beer....!
BTW - A week? - how big is it?.....doing it on your own, you should be able
to screed (get your sand/cement base ready) and lay about 30 sq m per
day.....

[1]
Don't bother buying mortar plasticiser unless you intend doing a lot of
building, you don't need anything in the screed, but in the mortar for the
edges, use about a teaspoonful of W-U-L per bucketfull of mortar (about 4
shovels of sand and one of cement - *don't* overdo it on the cement, a
common mistake by those not accustomed to working with it!)


HTH

--
If God had intended us to drink beer, He would have given us stomachs.