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Setts
 A selection of method statements for laying setts using SteinTec mortar.

Setts
Brief notes on the choices confronting the designer when specifying setts for pavement or carriageway construction
There are two distinct categories of setts to consider, shallow setts and full setts, each requiring a different approach.
What are shallow setts?
Shallow setts are those having depth less than width.
Precast concrete setts have long been manufactured having shallow depth and it is now common to manufacture natural stone setts in this format.
Specifying shallow setts makes a more economical use of the raw material used in their manufacture but the pavement construction requires to designed more carefully and there is an upper limit to the level of traffic which can be carried.  British Standards BS7533-7 & BS7533-10 provide guidance for the specification of shallow setts.
Note: A concrete base must be provided when specifying shallow setts.
What are full setts?
Full setts are those having depth not less than width.
For many ceturies the "golden rule" was that setts must be at least as deep as they are wide.  The heavier the traffic loading, the deeper the sett in relation to its width.  Before the advent of concrete and mortar, when jointing, bedding and supporting base were all unbound, this rule was very necessary.
Even with the development of high performance mortars and reinforced concrete for a base, we need to use full setts when the traffic loading exceeds a given maximum.
The deeper the sett in relation to its width, the more the strength of the pavement is taken by the joints between the setts.  So, with deep, full setts we can sometimes lay over an unbound or a bituminous base, even for heavy traffic.
British Standards BS7533-7 & BS7533-10 provide guidance for the specification of shallow setts.