General Specification chapter 81: what it requires from a bill of quantities taken from the model
General Specification chapter 81, "BIM for management, coordination and execution of building works", was published in a first edition in June 2026 (Tammuz 5786) as part of Israel's General Specification for building works. It sets what the model must contain at each stage and, among other things, requires a bill of quantities and a cost estimate based on the model. This page sums up what the chapter says about quantities, what it means for designers, contractors and quantity surveyors, and how to prepare.
What General Specification chapter 81 is and who published it
The chapter was published by Israel's inter-ministerial committee for the standardisation and computerisation of construction contract documents, in which the Ministry of Defence (Engineering and Construction Division), the Ministry of Construction and Housing (Planning and Engineering Administration), the Ministry of Finance (Accountant General) and the Ministry of Transport take part. It joins the familiar chapters of the General Specification (המפרט הכללי), and like them it opens with a section on methods of measurement and what the prices include. The full file is published on the committee's website, in Hebrew.
The chapter defines terms such as the model's level of detail and level of information, defines an IFC file as a file that all BIM software supports and that cannot be edited, and organises the work by stages: initial design, final design, detailed design, construction and as-built drawings. It concerns the designers, the contractor and the supervisor, and it is binding in a project whose contract documents include it.
Bill of quantities and estimate at each design stage
Table 81.02/02 of General Specification chapter 81 sets what is delivered at each stage. On quantities and cost it says:
| Design stage | What is required on quantities and cost |
|---|---|
| Initial design | A cost estimate per m² |
| Final design | A bill of quantities and a cost estimate based on the model, and the subjects that are not designed in BIM, where the contract documents require it |
| Detailed design | A full bill of quantities and a final cost estimate, based on the model and on drawings or details that will not be modelled |
In practice: where the contract requires a BOQ already at final design, the model has to be built so that quantities can be taken from it by the methods of measurement, and at detailed design the BOQ has to be complete, including what stays outside the model. The levels of detail the chapter sets rise accordingly: 100 at initial design, 200 at final design, 350 at detailed design for construction, 400 for design during construction and 500 for the as-built drawings. Another clause mentions level 400 for the as-built model, so it is worth fixing the level in the contract documents.
The contractor's quantity surveyor joins at the design stages
Clause 81.02.11 says, in our translation: "The contractor shall bring in a quantity surveyor on its behalf already in the initial design stages, in order to define the methods of measurement of the models." The same clause says the contractor will produce the bills of quantities from the models by using schedules, and that where the contract documents give no detail, what the prices of the components include follows the methods of measurement of the General Specification chapters. The methods themselves are covered on the page on methods of measurement in Israel and worldwide.
The notes for the designer say that when preparing a bill of quantities for the contract, the designer relies on the BOQ template at the end of the chapter and adds items as needed, and appendix B gives a sample reference table for preparing a BOQ from the model. So the designer and the contractor work from the same model, and agreeing the methods of measurement at the start reduces arguments later, in pricing, in procurement and in the accounts.
A Revit schedule counts elements as they were modelled. To become a bill of quantities it has to be matched to the methods of measurement, checked for double counting and completed with what was not modelled. Missing data is marked as missing, not as zero.
From the model to payment applications
During construction the chapter requires the model to hold current data for updating the as-built quantities and producing schedules, "as the basis for submitting accounts for payment" (clause 81.04.02, our translation). The model is also used for quantity calculations or for the percentage complete of each trade, linked to the methods of measurement. This is where a quantity calculation file behind the BOQ comes in: without a link between the line in the account, the element in the model and the method of measurement, the account and its variations cannot be checked.
And who pays for the model? Under clause 81.00.01 there are two options, as set in the contract documents: the cost is included in the contractor's bid and is not measured separately, or it is measured separately as a lump sum. Unless stated otherwise, the cost is included in the bid. So a contractor bidding for a tender with chapter 81 has to include the modelling work in the pricing and the budget, including the updates during construction.
How to prepare for General Specification chapter 81
- Decide at the start of design which elements are measured from the model and which from drawings, and the method of measurement for each.
- Build the model with the parameters the methods of measurement need: material, thickness, floor and zone.
- Keep the source of every quantity: an element in the model, a schedule or a drawing.
- Fix in the contract documents the level of detail of the as-built model and how the model is paid for.
In the price list for government and public bodies, under the Ministry of Defence tariff chapter 2.29 "Specifications and bills of quantities", the fee for preparing a BOQ is set by the building value; it appears on the page on what a quantity surveyor costs. Chapter 81 deals with the way quantities are produced and checked, and the fee is set by the tariff. In my work I measure the way a contractor does, from the model and from the drawings, and I compare the quantities of the AiN software with a Revit export, as explained on the page on AiN against Revit.
Under the chapter, the quantity surveyor is part of the design from its first stages. A quantity surveyor may be an engineer or a registered building technician, like Yaakov Avital.
Frequently asked questions
Is chapter 81 binding in every project?
It is binding in a project whose contract documents include it, usually in work for public bodies. A private project can adopt it in the contract, in whole or in part.
Who prepares the bill of quantities under the chapter?
The designer prepares the contract BOQ from the template at the end of the chapter. The contractor produces bills of quantities from the models, with a quantity surveyor on its behalf who joins already in the initial design stages.
Is the modelling work paid separately?
The chapter gives two options, as set in the contract documents: a cost included in the bid, or a separate lump-sum item. When the contract documents say nothing else, the cost is included in the bid.
Can the quantities from the model be used without checking?
No. A model counts what was modelled, and sometimes counts it twice. The quantities are checked against the methods of measurement and the drawings, and what stayed outside the model is added. More on these checks on the page on quantities from a Revit model.
Have a project? Tell me briefly what the project is and what already exists. When the project is a good fit, I usually reply with focused questions and a written quote.
Contact me for a quote* Created with AI for marketing, for illustration only. Not reviewed by Yaakov Avital and not professional advice. Every project must be checked on its own by a professional quantity surveyor and an engineer.