Working Drawings Handbook
components and the establishment of their work sizes
and permitted deviations is an entire field for study in its
own right. An obvious instance is that of pre-cast concrete
cladding panels with a compressible extruded plastic
section providing the weathertight seal between them
where, unless the greatest care is taken, the maximum
permitted gap between panels may be too great to hold
the plastic section in compression, while the minimum
permitted gap is too small for it to be inserted. The UK
Building Research Establishment’s paper on ‘Tolerance
and Fit’ is important reading in this connection, as is BSI’s
1999 publication BS EN ISO 6284.
The above discussion is intended as the most basic of
introductions to a complex subject. But it may be seen
how the whole of dimensioning practice becomes
simplified by the concept of the coordinating dimension.
The assembly of window and wall will be dimensioned on
the general arrangement plan as in 4.13, and if he is wise,
the architect will similarly designate the coordinating
dimensions on the component drawing (4.14).It will be prudent to note in the drawing set that this
method has been adopted. A note on the component
schedule or component drawing stating that ‘Dimensions
given for components are coordinating dimensions. The
manufacturer is to make his own reductions to give the4.12 Dimensional possibilities of
window/wall assemblies4.13 Opening on plan defined by its coordinating
dimension4.14 Component destined to fill the opening shown
in4.13is also defined by its coordinating dimension