Price books for private construction

In public works the source is prescribed and the designer answers for applying it correctly. In private work the source is chosen and the designer answers for its adequacy, which is a different and in some ways more exposed responsibility.

The difference shows at the point of dispute. A public bill built on the regional price book in force is defensible by virtue of having applied the prescribed source. A private bill is defensible according to how appropriate the chosen source is to the project, the territory and the period, which makes stating the source the first line of defence.

Source	Characteristics	Appropriate use
Regional prezzario	Free, updated annually, with explicit measurement criteria	A solid and readily defensible reference even outside public works
Sector price books	Broad coverage, periodic updates, structure oriented to professional practice	Projects where the regional book covers the intended work poorly
Chamber of commerce lists	Prepared with technical committee input, available in importable formats on dedicated portals	Provincial contexts where the local list is established practice
Supplier and contractor quotations	Aligned with the real market and the current moment	Specialist components and non standard supply, as a basis for price analysis
The practice's own final accounts	Reflect one's own way of working and one's own pool of contractors	The most reliable reference once the record is broad enough

The chamber of commerce lists warrant a note. Several chambers publish construction price lists, prepared with the support of technical committees and distributed through portals allowing download in formats importable into the main measurement software. They are official documents, updated periodically, and their usefulness increases in territories where they constitute shared practice between professionals and contractors.

It should be noted that certain tax and administrative procedures specify the reference price books admitted for quantifying works. In those cases the choice of source is not free even in private work, and it should be verified with the body responsible for the particular requirement.

This is the distinction to put in writing before delivering a bill to a private client, because misunderstanding it is the most frequent cause of dispute. Misunderstanding it is the commonest source of dispute.

The priced bill is an estimate of the cost of the works according to a stated source. The contract price arises from agreement between the parties and from the accepted offer, and may depart from the estimate in either direction without either figure being wrong.

The reasons for divergence are structural and worth spelling out. Price books report average values, and averages presuppose ordinary quantities: on small quantities the fixed costs of running a site weigh proportionally more. Site access, urban logistics and the need to work in an occupied building alter durations to a degree no list can anticipate. The level of finish required moves values more than any other variable. A contractor's organisation, its purchasing and its current workload affect the price offered independently of technical cost.

The most productive use of a private bill is not communicating cost to the client but building the comparison between contractors, and how the document is distributed determines the quality of the information obtained. How the document is set up decides whether that comparison is possible.

Issuing the bill with quantities and without rates produces bids comparable on the same quantity base, and allows the differences to be read as differences of organisation and purchasing. Issuing the bill already priced anchors bids to the figures shown, and reduces the information the comparison yields almost to nothing.

One precaution further improves the readability of the responses: asking for the bid to be returned item by item rather than as a total with a percentage discount. A uniform discount conceals the items on which the contractor is competitive and those on which it is not, and deprives the designer of the only information that is useful in negotiation.

It should finally be borne in mind that a share of the differences between bids concerns not rates but the reading of quantities. Asking contractors to flag the items where they disagree with the bill, before pricing it, catches take off errors at the point where they cost least.

Some situations recurring in private work are not satisfactorily covered by any list, and should be addressed through price analysis or supplier quotations. They should be addressed through price analysis or supplier quotations.

Work on occupied existing buildings involves protection, sequencing and restricted hours that price books, built on ordinary conditions, do not incorporate. Work on historic or listed buildings requires craft operations and conservation requirements that rarely find corresponding items. Bespoke supply, from joinery to special finishes, depends on dimensional and performance variables that no average value represents. Sites with difficult access, in historic centres or at height, shift the incidence of handling beyond the values implicit in the lists.

In all these cases the correct choice is the same: an item determined through documented analysis, which makes the rate contestable on technical grounds, rather than adjusting by eye a list item built on a different context. An item determined through documented analysis stays arguable on technical grounds.

For a practice working continuously on one type of project, the record of its own final accounts progressively becomes the most reliable source, and building it requires no particular tools. No public list reflects a local market with the same precision.

The method is to record, at the close of each project, the quantities actually executed and the prices actually paid, by operation rather than by total. After a few projects two pieces of information emerge that no list provides: the systematic divergence between one's own estimates and one's own final accounts, category by category, and the real percentage incidence of the work categories on the type of project handled.

The first allows subsequent estimates to be calibrated. The second allows an immediate plausibility check on any new bill, which is the quickest way to catch a unit error or a double count.

Three statements make a private bill legible and defensible, and their absence is what generates argument. Their absence is what generates argument.

The source should be stated, giving the price book or list used and its edition. Items determined by analysis should be flagged as such, with the analysis attached. The nature of the document should be made clear at the outset: it is an estimate of the cost of the works at the date indicated, not a price commitment.

To these it is worth adding a budget structure separating the cost of the works from the other elements of the operation, namely professional fees, charges, connections, taxes and a contingency allowance. A private client shown only the bill total reads it as the final cost of the project, and correcting that reading once works are under way is always harder than preventing it.