Construction resources: from BOQ quantities to crews, durations and a Gantt chart
Construction resources are the labour, equipment and materials that each item in the bill of quantities needs in order to be built. Crew sizes, durations and the order of the works all follow from them, and so does a large part of the pricing, the cost estimate and the budget of the project. This guide explains how to move from the quantities in the BOQ to resources, what you need to know from the site for the numbers to be right, and what AiN, the software I develop, already does.
Construction resources: three kinds for every item
Every item in the bill has three kinds of resources, and each is measured in a different unit:
- Labour. Tradespeople and helpers: formwork carpenters, steel fixers, blocklayers, plasterers and tilers. Labour is measured in work hours or person-days, and the crew size follows from it.
- Equipment. A crane, a concrete pump, scaffolding, a mixer and earthmoving machines. Equipment is measured in equipment hours or rental periods. Equipment hours are not work hours, and the two are never added together.
- Materials. The quantity in the bill, plus waste, delivery times and storage conditions on site. Material that arrives late stops a whole crew.
How one unit of work breaks down into hours, material and waste is explained on the page on construction inputs. Here we look at the whole project: how many people and how much equipment are needed, when, and in what order.
From quantity to load: how construction resources become a schedule
For a single item the arithmetic is simple: the duration is the quantity divided by one worker's daily output, divided by the number of workers. The full method, with links between activities and the critical path, is on the page on the construction schedule. For the project as a whole, something else matters: the load. How many person-days of each trade are needed in each week, and whether there is anyone to do them.
This is where the real problems show. The formwork crew grows during the frame and shrinks during the finishes. A crane is hired for a set period, and every delay extends the rental. A subcontractor comes on site for a particular period, not for the whole project. When the frame on the upper floors overlaps with finishes on the lower floors, two crews compete for the same crane and the same service hoist. A plan that does not check the load looks good on paper and runs late on site.
The load also turns into money. Every extra month on site is a month of a works manager, a crane, security and site cabins, as explained on the page on site overheads. A budget built without resources misses this part of the cost.
What you need to know from the site for the numbers to be right
The output rate in the professional literature is a starting point. On a real project the number depends on the crew, the method and the conditions, and two documented sources can give the same item outputs that differ by more than a factor of two. That is why every number needs a source, and a gap between sources is shown as it is, not averaged.
Someone who is on site every day knows things that are not in any table:
- Which tasks can go to workers without training, and which need tradespeople.
- How available crews and subcontractors are in the area, and what they charge at that time.
- The logistics around the site: truck access, room for a crane, parking and removal of waste to a licensed site.
- What happens when one stage is delayed, and who is waiting for it.
That is why good resource planning rests on the experience of a certified works manager, like Yaakov Avital, and on feedback from procurement: quotes from subcontractors and suppliers, delivery times and payment terms. These numbers change from project to project and from contractor to contractor, so the cost estimate and the budget are updated with them, including the variations that come up along the way.
Missing is not zero. An item with no output rate, quantity or crew is marked as missing, with the reason. It does not enter the schedule as if it were ready, and it is not given "zero days". That way you can see in advance where the plan is still incomplete.
Construction resources in AiN: what exists today and what is in development
In AiN the resources sit in the bill of quantities window, in the group of tabs for execution and finance. What works today:
- A resources sheet. For every item in the bill: duration, crew, equipment, materials and daily cost. The sheet is filled from the bill of quantities, and every assumption can be corrected.
- A detailed Gantt chart. One row for each item, with working days from a documented output rate and a sequence by floors. An item without an output rate, a quantity or workers stays in the output as "not scheduled", with the reason.
- Labour and equipment kept apart. Work hours and equipment hours are counted in two separate buckets, and no field adds them together.
- The concrete chapters: the start. For concrete items that have a code in a documented calculation source, formwork hours are calculated today. Steel fixing, pouring and piping are not in that source yet, so the item's hours are only a lower bound, and the item stays unscheduled and does not enter the totals as if it were complete.
- Rates. The starting labour rate comes from an external price list and covers only some of the trades. It is replaced with the project's own rates before anyone looks at costs.
In development, and not yet on the screens: deriving crew demand from the bill onto the timeline, a daily load for each resource against a capacity declared with a source and a validity period, and output rates for the finishes chapters from a further source that is still being checked. What the Gantt charts and the execution planning sheet look like is on the page on a schedule from a bill of quantities. Orders, invoices and budget control are described on the page on construction budget control.
A quantity surveyor may be an engineer or a registered building technician, like Yaakov Avital. In my work as a quantity surveyor for construction projects I measure the quantities the way a contractor measures them. Pricing and estimates are an extra service: verbal feedback on prices together with the client, with no commitment.
Frequently asked questions
What is the difference between resources and inputs?
Inputs are what goes into one unit of work: hours, material and equipment per m² or per m³. Resources are the picture of the project: which crews and equipment, how many, and when. The resources are calculated from the inputs and the quantities.
Can software decide the crew size on its own?
No. Software calculates demand and shows where it exceeds the declared capacity. The crew size, the capacity and the order of the works are decided by whoever manages the construction.
What do you do when an item has no output rate?
Mark it as missing and find out: from a documented source, from a contractor who does similar work, or from experience recorded on an earlier project. Zero is not an answer, because it makes the item disappear from the plan.
How do resources affect the budget?
Through the duration. A longer duration increases overheads, equipment rental and management, and an overlap that was not planned increases the need for extra equipment. A budget built with resources shows these costs in advance.
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.