This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol2", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Keep External and Internal work separate.
Abstract the items to be billed by weight first. Lead in flats, gutters, valleys, and flashings are abstracted and billed together, and will form the first item, the other items of weight following in order of value, as shown below in Fig. 44.
Internal Plumbing:-Commence with the items billed by weight, such as lead in safes. Lead in cisterns and sinks are abstracted and billed together. Follow on with runs of labours, then the various pipes according to size and weight, commencing with the smallest, as in Fig. 45.
Follow with strong lead pipe similarly set out. Sol deredbranch joints and soldered dead ends come next, according to size, the smallest first, as shown in Fig. 46; then the remaining Numbers, finishing with cocks of various sizes and descriptions, which are abstracted under a separate heading.
The last item will be the clause for tapping main, etc., and paying fees.