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How Can We Rebase and Roll Forward an Old Cost Plan Quickly When a Stalled Project Comes Back?

Quantity surveyors rebuild stalled projects' cost plans by hand when they restart. We build a tool that rolls forward base dates and shows its workings.

Updated 3 min readBy SpiderHunts Technologies

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Quick answer — TL;DR

When a stalled project restarts, the cost plan has to be brought up to date, and doing that by hand means reopening old workbooks and rebuilding the base date, allowances and inflation. We build a rebasing tool that reads the old cost plan, records its base date and assumptions, applies the indices and adjustments your surveyor chooses, and produces an updated plan with every change shown.

A project back from the dead

A client paused a scheme two years ago after planning. Now funding is back and they want an updated cost within the fortnight. The last cost plan is a workbook with a base date two years old, allowances for things that may or may not still apply, and a note in cell B3 that says 'inflation to be reviewed'.

The surveyor who wrote it has left. Rolling it forward means understanding every assumption first, then applying tender price movement, then re-examining the risk allowance, preliminaries and any market changes in specific trades.

Meanwhile the client, who remembers the old figure, is expecting a small uplift, and the design team wants to know whether the scheme still works before they restart. Everyone is waiting on the cost plan.

Why rebasing is painful

  • The base date and the index used are often not recorded clearly in the workbook.
  • Allowances and exclusions are in notes scattered across tabs.
  • Inflation and tender price movement have to be applied carefully so they are not double counted.
  • Some elements need more than an index update, such as trades with specific market pressures or changed regulations.
  • Nothing shows the client a clean path from the old figure to the new one.

What doing it by hand costs

Surveyor time spent reverse-engineering an old workbook. A risk of applying movement twice or not at all. A client who struggles to follow why the number rose, which leads to more meetings. And the same work repeated if the project stalls again.

Part of the planRebasing by handWith the tool
Base dateHunted for in notesRecorded and shown
Tender price movementCalculated in a new tabApplied from the index your surveyor picks
Trade-specific changesAdded ad hocEntered as named adjustments
Allowances and exclusionsScatteredListed for review
Explaining the changeWritten from scratchReconciliation from old to new generated

The rebasing tool

  1. The old cost plan is read and its structure, base date, allowances, exclusions and notes are extracted, with a language model helping to find assumptions hidden in text cells. A surveyor confirms what was found.
  2. The surveyor selects the index series and dates to use, from the data sources your practice subscribes to, and enters any trade-specific adjustments with a reason.
  3. The tool applies the movement and adjustments to the right elements and shows the result line by line.
  4. Allowances, exclusions and risk are listed for the surveyor to keep, change or remove.
  5. A reconciliation from the old total to the new one is generated, showing movement by cause, ready to explain to the client.
  6. The updated plan exports to your Excel template, with its new base date and assumptions recorded for next time.

Choosing the index and the forecast view is professional judgement and depends on the market at the time. The tool applies the choices and keeps the record straight.

A cleaner restart

The updated figure goes to the client with a clear bridge from the old one. Assumptions are written down for the next surveyor. If the project pauses again, the next rebase starts from a documented base rather than a mystery.

The same record helps during a live project too, when the cost plan has to be updated for a later start date or a change in procurement route.

Recognise the restart problem?

  • Old cost plans lack a clearly recorded base date.
  • Assumptions are buried in cell notes and hidden tabs.
  • Rolling a plan forward takes longer than it should.
  • Clients struggle to follow why a restarted scheme costs more.
  • The surveyor who knew the job has left.

FAQ

Frequently asked questions

The questions readers ask us after this guide.

Still have a question?

Ask us directly — a senior engineer will get back to you.

Ask about your project

Which indices does it use?

Whichever your practice has access to and chooses. We load the series you subscribe to, as their terms allow.

Can it tell us what inflation to forecast?

No. Forecasting is a surveyor's judgement. The tool applies what you choose and records it.

Does it work on cost plans not laid out in NRM order?

Yes, with more mapping at the start. A surveyor confirms how elements line up.

What affects the cost?

How varied your old workbooks are, how many index series you use, and the output formats you need.

Keep reading

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