Replacement contractors need a clean handover

When a contractor leaves a part-built job and another picks it up, the price and programme for the next phase depend on the record left behind. Drawings at their true revision, the status of every design submission, approved materials, a numbered variation register and a certified account for the outgoing package are what the incoming contractor prices against. If the client cannot hand those over cleanly, it pays for the gaps twice: once in qualifications and risk allowances at tender, and again in arguments later.

What happened at Daubeny

Mace Construct is to leave the Daubeny Buildings laboratory project at Oxford Science Park at the end of 2026, once its current package is complete. Construction Enquirer and Building put the scheme at £200m, while Construction News reports it at £184m.

Mace has been on the job since 2024, first for Oxford Science Park and then for the Ellison Institute of Technology (EIT), which bought the site last year. Construction Enquirer reports that Mace topped out two of the three six-storey lab and office buildings before work stopped last October following the acquisition. A Foster + Partners redesign now turns three standalone buildings into one linked research complex. Sections of the upper floors and envelope will be stripped out, existing plant removed and two large atriums added, with most of the concrete structure retained.

Building reports that Mace had been expected on site until 2030, that the next phase is set to be let as design and build, and that it understands Sir Robert McAlpine has been told it will finish the work. EIT has not formally named the replacement. Both EIT and Mace describe an agreed transition, and Mace says its focus is on "ensuring a smooth transition".

It is not a one-off. Construction Enquirer notes McAlpine itself recently handed the Agratas gigafactory in Somerset to TSL after a change in delivery strategy, and Morgan Sindall is gearing up to restart a stalled Blackpool courthouse after ISG's collapse.

Daubeny is the orderly version of a changeover, agreed in advance with months of notice. That is exactly why it is worth studying. If the handover record is weak on an agreed exit, it will be far worse when the outgoing contractor has gone into administration and the document controller has been let go.

Why changeovers cost more than they should

An incoming contractor taking a design and build appointment over a part-built, part-stripped structure is accepting design responsibility for interfaces with work it did not build. It will price what it can verify and qualify what it cannot.

Every missing record turns into one of a few things. A survey the incoming team has to commission before committing. A qualification in the tender. A provisional sum. A risk allowance buried in preliminaries. None of those are free, and the client pays for all of them whether it notices or not.

On a retained frame with strip-out, the unknowns are specific. Which drawing revision was actually built to. Where cast-in items and penetrations really are. What temporary works were designed and by whom. Which materials and products were approved through submittals and which were swapped on site. What the testing and inspection record says about the concrete being kept.

On the outgoing side, the commercial loose ends are just as real. The final account for the outgoing package. Retention and the defects position on retained work. Collateral warranties and third party rights. Materials off site. Subcontract orders that may or may not be useful to the next contractor. If the variation register lives on the outgoing QS's laptop and the valuation history sits in email chains, the client loses the commercial story of the job the day the team demobilises.

The record should belong to the project

Most developers rely on the main contractor's document control. That is fine while the contractor is there. When it leaves, access to its common data environment usually ends, and what comes back is a zip file of PDFs with filenames that made sense to someone who has now moved on.

The fix is simple to describe and needs discipline to run: the client should hold the live project record in its own name from day one, with the main contractor working in it rather than alongside it. That means the drawing register and information required schedule (IRS), approved technical submittals, RFIs and their answers, numbered variations and the valuation and certification history all sit somewhere the client can see without asking.

That is the arrangement SubTrada is built around. Main-contracting and client profiles sit on the same platform, so drawings are auto-filed at revision with the IRS showing what was late or on time, submittals are approved by QR against the element they relate to, and every approved variation carries an instruction number that feeds the valuation certification schedule. When the delivery team changes, the history does not leave with it.

Changeover checklist for clients and incoming contractors

Run this as soon as an exit is agreed, not in the last fortnight before demob.

• Drawing register: every drawing at current revision with status, superseded issues marked, and the revision actually built to confirmed for retained elements.

• IRS position: outstanding information requests, dates requested and issued, and which items ran late, so the incoming team inherits a real design programme.

• Approved submittals and samples: technical submittals linked to the element and drawing they cover, with any site substitutions recorded.

• Retained structure record: pour records, test certificates, inspection sign-offs, temporary works designs and as-built surveys for anything being kept.

• Open RFIs: questions raised, answers given, and anything still waiting on the design team.

• Variation register: every instruction numbered, valued, and marked as agreed, disputed or pending.

• Valuation history: payment notices, any pay less notices, certified sums by package and the agreed or disputed final account position.

• Supply chain list: who installed what, current insurance with expiry dates, warranties held, and which specialists the client or incoming contractor may want to re-engage.

• Commercial close-out: retention, defects responsibility for retained work, collateral warranties and materials off site, each with an owner and a date.

For the incoming contractor

Ask for the tender to be issued from the client's controlled drawing set at named revisions, not a forwarded bundle, and qualify against those revisions in writing. If the drawings are pulled straight from the register at tender issue, the revision you price is the revision on record, which is how tender issue works on SubTrada.

Do not assume the outgoing specialists are a safe bet just because they know the job. Run them through the same PQQ, insurance and financial checks you would use for a new supplier. Some will be excellent and worth re-engaging quickly. Others will have been carrying the outgoing contractor's late payments and may be weaker than they look.

Get the certified valuation position before you price. Knowing what has been paid for, and what was disputed, tells you a lot about which work is genuinely complete.

For the outgoing contractor

Treat the handover record as a deliverable, not a courtesy. Agree its contents early, get it signed off, and close the final account for your package before your commercial team moves to the next job. A clean exit protects your retention and your reputation with a client who may well be back in the market.

FAQ

What should a client get from an outgoing contractor at handover? At minimum, the current drawing register and IRS, approved submittals, open RFIs, the retained works record, a numbered variation register, the valuation and certification history and a supply chain list with insurance and warranties. The contract should say this before anyone needs it.

Can subcontracts be transferred to the replacement contractor? Sometimes, usually by novation, which needs the agreement of everyone involved and depends on the subcontract terms. Plenty of clients find it cleaner for the incoming contractor to re-procure, using the outgoing supply chain list as a starting point.

Who carries the risk of existing work on a design and build changeover? That comes down to the contract. Incoming contractors will try to exclude or qualify latent defects in work they did not build. Clients can narrow that gap with surveys, a full retained works record and reliance on existing design where it can be given.

When should handover planning start? The day the exit is agreed. At Daubeny, with the exit public at the start of October and Mace due off by the end of the year, that is roughly three months, which is workable if the record has been kept properly all along and tight if it has to be rebuilt.

My view: put the handover record into the appointment at the start of every job, name its contents, and tie sign-off to the final account. Clients who do that will find a contractor change is an inconvenience. Clients who do not will pay for it in the next contractor's qualifications.