Plastic
under the paving?
Don't
be fooled by sales consultants telling you that you should put plastic sheets
under the paving to prevent weeds and grass from growing through the paving.
This
is a myth. For grass or seeds to develop and grow they need water, oxygen, the
correct temperature and light. Paving an area and putting grouting between the
bricks will eliminate all of the above, resulting in no growth of any plants
from under your paving. A common example to prove my point is that if a pile of
bricks or building material is left untouched on your grass for a long period
of time the grass under the bricks and rubble will die.
What
is however important to add here is that if bulbs are not removed these often
can push through making your bricks bulge. This will happen with or without
plastic. It is therefor important to ensure that your paver removes all visible
roots and foliage before compacting.
Another
good reason not to put plastic under your paving is that the plastic stops the
water from draining through the paving. If the paving is laid on a steep
gradient it is bound to move if laid on plastic.
Another
good reason not to use plastic under the paving is that it badly effects
particle interlocking in the bedding sand which as mentioned will result in the
brick not being able to bed in the sand resulting in the bricks moving.
The
only time Style & Craft Paving recommend using plastic sheeting is as a
barrier between clay and a suitable material such as G7. Depending how bad your
clay may be, we remove a layer of between 75 mm - 100 mm. We then compact the
base and lay plastic sheeting before replacing the removed clay with a suitable
sub base material. Style & Craft Paving have used this method with great
results in the past, however without soil testing an engineers specifications
the success of this can not be guaranteed.
Clay
and underground water are two enemies of successful paving, in fact it is
impossible to successful pave on top of clay or a wet base without solving the
problem first, like removing the clay or installing drains. This subject is for
more in depth discussion at a later stage.
