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Any paving project requires a certain amount of heavy lifting and expense. Therefore when going through this level of financial commitment you want to make sure things are done properly.
Excavating new paving out to an adequate depth is the only way to guarantee a secure base. However the removal of excavated spoil and the spreading of compactable sub base is labour intensive and expensive.
Therefore it is understandable to seek if you can pave over existing crazy paving surfaces. In this article we will explain the variables involved in answering the question, 'can you pave over crazy paving?'
Normally the answer will depend on the specific particulars relevant of your specific project.
One of the most constricting factors when paving over old surfaces is the surrounding surface levels. The most important of which is the damp proof course of adjoining buildings.
This is the level of the building with a waterproof layer built into the wall. This is normally about 200mm from the surrounding ground level. The damp proof course is to prevent surface and storm water splash from absorbing into the structure.
Therefore paving over existing surfaces can increase the risk of damp inside the home. Building regulations require you keeping ground surface levels 2 brick courses below the damp proof course.
The damp proof can be identified by an extra thick, mortar layer or where external rendering begins. If your surrounding ground is already dramatically below the damp course this allows you to raise levels further.
In this scenario you could build on top of existing crazy paving or other masonry surfaces.
However 85% of the time existing crazy paving levels will not provide a suitable base for new paving.
To ensure consistent surfaces new paving levels should adjoin surrounding levels harmoniously. This includes pathways, garages, gateways, drainage channels and pavements.
There should be no ramping, bulging or sloping levels implemented to match into surrounding surfaces. Therefore most of the time surrounding levels will not allow you to pave over crazy paving.
Inspect the paving’s surface
The problem with paving over existing crazy paving is not knowing how robust the underlying base is. With all paving, a solid base at the correct thickness is vital to ensure no movement or displacement.
This is to guarantee the new surface does not crack and can withstand the demands placed upon it. However you can get an idea of how well built existing paving is by inspecting its surface.
If paving has excessive cracking and visible movement you should not pave over it. Also long, fault line, cracks are evidence of subsidence and expanding tree roots.
Broken edges and sumping is also typical of paving with an inadequate base. If the whole surface is solid with no visible cracks it probably has a sound base.
Thumping with a large piece of vertical timber can sometimes also give you an indication of durability. If you get a hollow sound or feel vibration underfoot the surface is less solid.
However if the surface resists any vibration and you feel vibration shocks in your hands it is very solid. In this case it is ‘probably’ ok to build on top of if the surrounding levels allow.
Depending on the ‘existing state’ of your crazy paving you may choose to pave over it with new paving. If the existing crazy paving is free from cracks and accommodates a suitable level it is ok to pave over.
Should the paving be full of cracks it could be susceptible to further movement and therefore failure.
However if the there are no cracks ask yourself this fundamental question. Will the new paving look better and reach a harmonious level if you pave over the existing crazy paving?
Removing existing paving and installing a robust sub-base provides piece of mind there will be no failure in the future.
It will also provide freedom to choose your preferred level which will be consistent and in line with your drainage strategy.
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If you are planning on paving over the old paving yourself check out our recommended paving equipment list.
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Paul Nicolaides has over 30 years of recreational gardening and 20 years of professional landscaping experience. He has worked for landscape contractors including design and build practices across London and the South East. In 2006 he qualified with a BA Hons degree and post graduate diploma in Landscape Architecture. In 2009 he founded Ecospaces an ecological landscaping practice which aims to improve social cohesion and reduce climate change through landscaping. In 2016 he founded Buckinghamshire Landscape Gardeners which designs and builds gardens across Buckinghamshire and the South East. This blog aims to provide easy problem solving information to its audience and encourage others to take up the joy of landscaping and gardening.