Demolition BOQ: what goes in, what is marked as missing, and why zero is the costly mistake
A demolition BOQ (bill of quantities) looks short: one building, a few items, a unit of m³ or tonnes. In practice it is the chapter in which two quiet assumptions, waste density and the hazardous materials survey, decide most of the total, and in which the most common mistake is a zero instead of "missing". This page explains what goes into a demolition BOQ in Pinui-Binui urban renewal (demolish and rebuild, where the residents get new flats) and in demolition and rebuilding projects, and what gets marked as a question.
What is in a demolition BOQ
| Item | Unit | Where the quantity comes from |
|---|---|---|
| Demolition of an existing building | m³ | Built area times average gross height |
| Selective dismantling | m² | Only when there is a conservation or reuse requirement |
| Waste removal | tonne | Volume times density; the density sits in a visible cell with a source |
| Asbestos and hazardous materials | m² | From the hazardous materials survey; without a survey this is missing data |
| Disconnection of existing utilities | lump sum | Water, sewage, electricity, gas and communications, according to the authorities' approvals |
Under the General Specification for building works (Israel's inter-ministerial specification), dismantling parts of structures, including pipelines, concrete channels, piles, subbase layers and underground structures, is measured as a lump sum or as stated in the particular methods of measurement, and backfilling the pits created by the dismantling is measured by volume in m³, separately for each fill material. So here too the project's methods of measurement decide, and the bill states what each item is measured by. More on the rules on the page methods of measurement.
The two alternatives that must not be added together
Full demolition and strengthening of an existing building are two alternatives for the same building. A bill of quantities contains one of them; both together are double counting. In urban renewal projects the decision between strengthening and demolition and rebuilding is made before the bill, and if it is still open, the bill is written as two separate alternatives, each marked as an alternative. On the differences between the routes, see the page TAMA 38 BOQ. TAMA 38 is Israel's national plan for strengthening existing buildings against earthquakes, usually with added floors.
The assumption that decides the total: waste density
Waste removal is measured in tonnes, but what is measured from the drawings is volume. The conversion goes through density, and the density is not a measurement but an assumption: reinforced concrete, blockwork, finishes and packaging give different densities, and the heap after demolition bulks up. In my work the density sits in a visible cell in the calculation sheet, with a source and a date, not inside the formula. That way whoever checks the bill sees what was assumed, and if the developer or the contractor wants a different density, one cell changes and the bill updates. On the difference between a design quantity and a quantity measured during construction, see the page physical quantity, BOQ quantity and order quantity.
Zero is not an answer. Without a hazardous materials survey, the asbestos item in the bill is not zero but "missing". A zero there is probably the most expensive mistake in a Pinui-Binui bill, because hazardous materials are removed under regulatory requirements and by licensed contractors, with a price and a schedule of their own. The survey is a project document, and until it arrives the line stays open.
Working in an occupied building and an existing neighbourhood
Demolition in the middle of a neighbourhood affects the preliminaries chapter as much as the construction programme. This includes solid hoarding and traffic separation, temporary passages for residents who stay, additional safety signage, noise restrictions by hours, dust and vibration control, and phasing of the works. Pricing phasing is not linear: an extra phase is not "a little more", it is another site set-up, more hoarding and more removal. In most cases it is worth writing these items as visible items in the preliminaries, so that the contractors price them rather than absorbing them into a discount.
Before demolition there is also documentation: a photographic condition survey of the neighbouring buildings, a baseline reading of settlement points, and in some cases monitoring during the works. These are items that can be measured and put into the bill, and they usually appear in the consultants' requirements rather than in the demolition drawings. On ground, excavation, foundation and shoring matters, check against the project's soil report and with the geotechnical consultant and the structural engineer.
What a professional quantity surveyor adds here
Whoever measures demolition by the drawing alone multiplies area by height and is done. A quantity surveyor who comes from the field, an engineer or a registered building technician who worked on site, like Yaakov Avital, asks what is inside the building and what is under it. For example: the demolition drawing shows a four-storey building, while the soil report describes an old basement that does not appear on the existing drawings. Measuring by the drawing will count four storeys. A professional check flags a question to the architect and the structural engineer about the basement, the foundations that stay in the ground and the backfilling of the pit. They decide, and the bill says so in writing.
In demolition, the quantity takeoff starts with a survey of what exists, not only with the drawing. A quantity surveyor who visits the site sees things the drawing does not show, and the quantity takeoff improves accordingly.
Frequently asked questions
Which unit is demolition measured in?
In most bills in m³ of building, by built area times average gross height, and waste removal in tonnes. In some projects the demolition item is written as a lump sum, and then the description must say exactly what is included.
Who prepares the hazardous materials survey?
A qualified surveyor, according to the regulatory requirements, not the quantity surveyor and not the contractor. The survey is a condition for writing the asbestos item, and without it the item is marked as missing.
What is the difference between a demolition BOQ and a dismantling bill?
Full demolition measures a whole building. Selective dismantling measures elements that are taken apart carefully for conservation or reuse, in m² or in units, and its price is completely different. The two are not interchangeable.
How does it fit into the bill for the new building?
As a separate chapter at the start of the bill, before the earthworks, with a clear boundary between demolition and excavation, so that the pit, the backfill and the removal of old foundations are not counted twice. Writing that boundary is the work of a quantity surveyor for construction projects.
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.