TL;DR: A resource planning spreadsheet shows who is booked and when. It can’t check bookings against fee budgets, update when a programme moves, or warn you about an overrun. Business spreadsheets in general also carry errors far more often than owners expect. A spreadsheet suits a very small team. Once updating takes longer than planning, put staffing, fees and timesheets in one system.
The staffing spreadsheet starts as a tidy grid. Six months later it has a tab for every month and two copies that disagree. Nobody wants to edit it, because nobody trusts it.
A resource planning spreadsheet is a sensible first tool. It costs nothing, everyone can open it, and you can build it in an afternoon. The limitations of using spreadsheets for project staffing show up later, when the business has more people and more live jobs, and the fees keep moving.
Planning consultants, engineers, architects, surveyors and ecologists all hit the same wall. The sheet records who is booked. It doesn’t know what the fee allows or what the timesheets say.
Below, we cover what a staffing sheet can’t do, how often spreadsheets go wrong, how the problem looks in each discipline, and the signs that yours has stopped working. We also cover what to use instead.
What are the limits of a resource planning spreadsheet?
A resource planning spreadsheet shows who is booked on which project and when. It can’t compare those bookings with the fee budget, update itself when a programme moves, or warn you when a booking runs over. Those gaps stay hidden until timesheets are reconciled, usually after the margin has gone.
Four limits cause most of the trouble:
- No link to the fee. You book days against a person, but the fee sits in a proposal. The sheet can’t tell you a booking has used most of the budget.
- No live actuals. Timesheets live in another system, so planned and actual hours meet only when someone copies them across.
- No alerts. A double-booked specialist stays double-booked until somebody spots it.
- One editor at a time. When two people change the sheet, or two copies circulate, the plan splits.
Scale makes each limit worse. A business we’re working with plans all its staffing in one spreadsheet. It runs to hundreds of rows across six months, and the team says it’s impossible to keep up to date. The sheet has outgrown its job.
The picture also moves fast. The RIBA Future Trends report for August 2026 found architecture workloads about 9% lower than a year earlier, and staffing about 5% lower, on average. A plan built on last quarter’s assumptions goes stale quickly, and revising hundreds of rows takes real effort.
Spreadsheets carry more errors than most owners assume
Panko’s review of spreadsheet research is the standard reference. Seven field audits of 367 real spreadsheets found errors in 24% of them. The audits from 1997 onward, which used better methods, found errors in 91% of 54 spreadsheets. In lab tests, 998 people built 1,170 spreadsheets from simple word problems. Half of them (51%) contained errors, even though most ran to only 25 to 50 cells.
A later literature review led by Pak-Lok Poon puts the figure at 94% for spreadsheets used in business decisions. The summary page doesn’t state a publication year, so treat it as supporting evidence rather than a fresh measurement.
Both sources look at spreadsheets in general. Neither studies staffing sheets, so read the figures as a warning, not a count of your own errors. The usual faults still apply: an overwritten formula, a number typed over a total, a month copied across with last month’s assumptions. Add a second copy emailed “just for the project leads” and the plan starts to split.
Why doesn’t a resource planning spreadsheet show whether a project is profitable?
A staffing sheet records planned days for each person. The fee budget sits in the proposal and actual hours sit in timesheets. With three sources, nobody sees an overrun until work in progress (WIP) is reconciled, which is often after the invoice has gone out.
The gap shows most when the scope changes. The client asks for more, the fee should move, and the plan should follow. If a variation never reaches the sheet, the team keeps working to the old budget. Our guide to contract variations and percentage fees explains why a percentage fee doesn’t always keep up with extra work.
Actuals are the other missing piece. The RIBA Business Benchmarking Report 2023 found that 60% of responding chartered architecture businesses record the time their staff spend on billable work. Without recorded time, there is nothing to set against the plan.
Timing matters too. A PBC Today summary of Deltek’s resource planning paper argues that planning should shape the fee and programme before either is agreed. It adds that plans need updating after award, when programmes and instructions change. A sheet that sits apart from the proposal does neither. For the architecture version of this problem, see our guide to resource planning for architects.
What this looks like in each discipline
The fault is the same everywhere. The trigger differs.
- Planning consultants: a resubmission or an extra request from the local planning authority (LPA) lands outside the fee, while the sheet still shows the planner free next month. See how we work with planning consultants.
- Engineers: one specialist reviewer sits on two jobs in the same week. A project can fit spare hours on paper and still clash with a specialist committed elsewhere, as the same PBC Today article notes.
- Architects: the budget for a RIBA stage runs out early, but the sheet keeps the team booked as planned.
- Surveyors: an extra site revisit gets booked on the day and never reaches the plan.
- Ecology: survey seasons fix when work can happen. Miss a survey window and the visit can slip by months, so every booking behind it moves too. In a sheet, someone shifts each row by hand.
When is a resource planning spreadsheet still good enough?
A spreadsheet works while one person can hold the whole plan in their head and update it in minutes. When updating takes longer than planning, or two people disagree about which copy is current, the sheet costs more than it saves.
We won’t give you a headcount, because the trigger is how the business behaves. Look for these signs:
- Updating the plan takes longer than the planning itself.
- More than one copy is in circulation.
- You learn about a double-booking from the person who is double-booked.
- A fee variation gets agreed and nobody changes the plan.
- Nobody can say why last month’s plan was wrong.
If two or more sound familiar, the sheet probably costs more than a system would. That is judgement, not a measured threshold.
What should replace a staffing spreadsheet?
Use a system that ties bookings to fee budgets, timesheets and work in progress, so an overrun shows while the work is running.
Ask four things of any tool:
- One record per project that holds the fee, the bookings, the time and the invoices.
- Actual hours that flow in from timesheets without copying.
- A warning when bookings pass the budget.
- A way to plan before a fee is agreed, not only after.
A system won’t fix weak estimates. The PBC Today piece makes the same point: software shows conflicts, but only realistic inputs make it useful. Deltek’s 2026 Clarity study of 375 senior leaders at architecture, engineering and consulting firms found 33% naming unintegrated manual systems among their project management challenges. It also found 38% pointing to automating manual processes as a route to higher profit.
Woolf Bond Planning, a Reading consultancy, ran projects from a master Excel sheet, with timesheets in Word documents. We moved it to WorkflowMAX with Xero in just over a month. After two months, its planners see open WIP on every project. The planning consultancy case study has the detail.
If you don’t have a system yet, our system implementation service covers the move from spreadsheets. If you already have one and still plan in a sheet beside it, system optimisation is usually the quicker fix.
When to move staffing out of the spreadsheet
A staffing spreadsheet plans hours. It doesn’t plan margin, because it has no view of the fee or the actuals. Errors rise as the sheet grows, and the signs of outgrowing it are easy to see: slow updates, rival copies and double-bookings found late.
If your sheet already takes longer to update than to plan, book a discovery call. We’ll look at how your staffing, fees and timesheets could sit in one place. Margin you can see is margin you can keep.
