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 paving comapny 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 successfully 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.