Sub Base Construction

The first thing to consider when preparing to lay paving is the provision of a suitable sub-base. This will work as the foundation for your paving. The depth of the sub-base will vary depending on soil type and site conditions, but generally 100mm of consolidated scalping (type 1) or hardcore (broken bricks and concrete) will provide sufficient strength for most paving jobs. On clay or unstable soil a greater depth of base will be required. Some landscape architects or very conscientious landscapers will specify a concrete foundation / base that the paving will then be laid on. This is a very successful method of construction for a sub-base but is generally better left to the professional contractor as mistakes are very hard to correct.

An important consideration when excavating for your sub-base is the finished level of the paving. It must be 150mm below the damp proof course or two bricks down, a slight variation in this height is acceptable but never go below 100mm unless drainage channels are to be provided. At this stage you should also bare in mind, rain water run off. In most cases your patio should gently run away from the house or any building except where drainage is to be provided. A slope of 1:100 or 1:50 will be sufficient, but depending on the lye of the surround land the fall could change. The sub-base should slope at the same rate as the finished level of the patio.