Last edited 18 Dec 2020

Rule of thumb


[edit] Introduction

Rule of thumb is an English phrase that has been in common use since the 17th century. It describes a method of doing things which, although not scientifically verified, is broadly correct although it may not be strictly accurate or reliable in all applications, even though it may have proved successful on past occasions.

It may be that a rule of thumb is eventually proved in science to be correct, althouth it may still be referred to as a ‘rule of thumb’ – see below.

[edit] Use in construction

Builders of the past would have used rules of thumb in construction. Gothic cathedrals eventually would soar in height as master masons learned through experience to understand certain relationships e.g, the height of a tower in relation to its base and wall thickness; the depth of foundations according to soil conditions, or the diameter and spacing of piers to support the masonry above.

Advancement would typically be through making mistakes - frequently catastrophic - and learning from them. A classic example is the collapse (in 1237) of the main tower at Lincoln Cathedral, and the collapse (1210) of the south-west tower of Chichester cathedral followed in 1635 by the collapse of its north-west tower.

Rules of thumb are still used today by construction professionals as they can give a basis from which a more detailed design may be delivered.

Examples of rules of thumb are:

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