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- Concrete usually comes in ready mixed
pourable form or barrow mix form. Concrete pouring is OK as long
as there is access for the truck's shute to reach the site,
otherwise use a barrow mix service. Normally the minimum charge
is for one cubic metre plus delivery cost.
- Mixing your own concrete is not worthwhile
unless you need only a very small quantity. The main reason is
the amount of time involved and the quality of the concrete. If
you do want to mix a small amount , the proportions should
be about 3 parts stone, 2 parts sand, 1 part cement depending on
the strength and finish required.
- Setting out timber shuttering or formwork and
strengthened with stakes into the ground or stabilised with some
other device will be necessary. Checking levels constantly is
required and the use of long lengths of timber, string lines and
of course a spirit level will help.
- It is often required to create a compacted
sub layer to support the concrete for building a slab floor etc.
This is done by dispersing a layer of MOT stone or "Crush and
Run" as it is sometimes called, across the area and compacting
it with a Wacker Plate (a trench compactor can be used if space
is limited) which can be obtained easily from any good hire
shop. If the concreted area is going to be subject to heavy
weights or traffic, it will be very likely that reinforced steel
mesh will need to be placed into the area before concreting, and
supported off the sub layer with small purpose made spacers
available from most builders merchants.
- Strip foundations are required beneath all
brick wall constructions. Digging out an approximately
600mm wide trench to a depth specified by your local council and
filling with concrete to a depth of approximately 300mm once the
solid sub floor has been established will usually be enough to
support a 300mm cavity wall 2 storeys high. Confirm with local
building inspectors as ground and regulations vary across the
country.
- Never "TAMP" concrete. Tapping on the surface
of wet concrete with a straight edge or plank on edge brinks the
water to the surface and with it the cement, leaving below a
weakened mix and often a flaky surface in the following days.
- In order to get the concrete to the desired
level, you should use a sawing action using a straight edge
guided by the shuttering or formwork. Tapping the formwork on
the outside gently with a hammer will also help the concrete to
fill up any voids. If the sawing action leaves some depressions
or hollows on the surface, fill up these voids and re-saw that
area before moving on.
- The type of finish required may vary
according to the usage of the area. Sometimes a soft sweeping
brush dragged lightly across the concrete after a while (usually
about 1 hour depending on weather and temperature) and a border
applied using an edging trowel (this has one rounded edge which
runs down the inside of the shuttering) can produce a
professional appearance and provide a good grip underfoot.
- With regard to quantities: One cubic metre of
concrete will cover 10 square metres at a thickness of 100
millimetres which is more than enough thickness for walking on
and if reinforced, strong enough to accommodate an average
family car.
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