Prototype and mock-up approval

At a glance

Square brackets are placeholders. No tolerance is given: take it from the tolerance clause of your specification, not from a general guide. The criteria are practice, not a standard.

What a mock-up is for, and when it is worth asking for one

A control sample shows a finish. A prototype is a full-size working example of one item, and a mock-up is a full-size or part-size representation of an element or a whole room. They answer questions a drawing and a swatch cannot: does it fit, does it feel right, does it work, does it meet the wall properly. Designing Buildings, a commentary site, lists similar reasons for mock-ups in construction: to confirm that a product meets the specification, to review its appearance, to show how installed materials interact and where trades meet, to refine installation before the main work, and to help people who find drawings hard to read.

Not every item needs one. Our design development page says finish mock-ups and prototypes are available for complex or high-value commissions, and our how we work page says simpler items may go to production after sample approval. So say in the specification which items get a prototype, and do not assume it. Reasons to ask for one:

• Repeated items. A hotel room made many times is worth one careful build first.
• Comfort-critical seating. Use the sit-test protocol on the prototype.
• Moving or mechanical parts, where action and noise only show in use.
• Tight interfaces with the building, where a scribe or a shadow gap decides the look.
• A detail that depends on scale, such as a profile, an inlay or a curve.

Put it in the tender, not after it. Designing Buildings says the specification should set out the requirements and test procedure for a mock-up, with the pass or fail criteria and any witness requirement, and that including them in the tender documents lets the cost sit in the original bid. It adds that once a supply contract is let, comments on mock-ups can only be made within what the contract allows, and a comment that changes the requirement may mean an adjusted sum and more time. Agree how the mock-up is handled alongside the commission before it is made, as for samples. Where it sits among samples is on the sample hierarchy sheet: a control sample fixes a finish, a prototype or mock-up tests scale and fit, and a first article proves the first real piece.

Eight groups of checks, and a way to run the review

The table at the top is the checklist. Send it to the maker with the drawing revision before the review, so that both sides are looking at the same things. The plan below shows where each group sits on an invented guestroom, but the same eight groups apply to a single chair or a wall unit.

1. Measure first (groups 1, 5 and 6): sizes, junctions and services, with a tape and a level, before anyone gives an opinion.
2. Then look (groups 2, 7 and 8): finish under the named light beside the control sample, papers beside the build, brand points against the written standard.
3. Then use it (groups 3 and 4): sit, reach, open, close, lock, lift.
4. Decide each group on its own, and record who signs it, before the overall decision.

Judge finish as the control sample was judged. Use the same named light, the same viewing distance and the same orientation, and write them on the record. Our sample sheet explains why: two surfaces that match under one light can differ under another.

Keep a photo record. It is the memory of the review, and it lets people who were not there see what was agreed.

Pass, conditional or fail, and who signs

Decide each group, not just the whole. A mock-up can pass on fit and fail on hardware, and a single overall tick hides that. State the criteria before the review, with the figures as placeholders to fill in from your specification, and record one outcome per group:

One named person signs for each group. Use names, not only job titles, so the record still means something a year later. The people who usually attend, and what each signs for:

The decision applies to one drawing revision and to the items named. If the drawing changes afterwards, the approval does not follow it automatically: the change is recorded and approved again.

Approve, then release: where the mock-up sits in the programme

A mock-up is a hold point. Production of the remaining items is released only after a signed decision against a named drawing revision, and a verbal “looks good” releases nothing. The drawing shows the gate and the loop: a fail sends the work back for a revised mock-up, and a conditional decision records the changes and then releases.

Build the time in, and do not assume it. We give no duration here, because it depends on the item, the maker and who else has to attend. Ask the maker how long the mock-up takes to build and how long it needs for review, put both in the programme, and leave room for one repeat. A hospitality consultant’s opinion piece advises building a model room early, so that changes come before large orders are placed. That is the point of a hold point: a change is cheapest before production starts.

Where it sits in the Plan of Work. The RIBA Plan of Work 2020 says specialist subcontractors’ design work belongs in Stage 4, and that Stage 5 is the making and building, with inspection. A mock-up that settles the design therefore belongs before production is released, late in Stage 4 or early in Stage 5 on our reading. The Overview does not name prototypes or mock-ups for furniture or joinery: see where bespoke work sits in the RIBA Plan of Work.

After approval: the mock-up becomes the benchmark

What happens next should be written down before the review, not decided on the day.

• Tag, photograph and keep it. The approved mock-up is the benchmark where the work is made, until [practical completion]. Mark it “mock-up, not for use” and keep it out of strong light.
• Check the first article against it. The first piece off the production run is compared with the mock-up and the control sample before the rest are released. How far a delivered piece may differ is on the snagging acceptance criteria sheet.
• Change only by written variation. A change after approval states its effect on programme and on the contract sum before work changes, and is entered on the substitution register if it swaps a material, finish or supplier.
• Decide what the mock-up becomes. It may be kept as a benchmark and then returned or scrapped, or, if it was built to production standard and everyone agreed beforehand, it may be installed in the finished building. Do not assume the second: whether a mock-up can become part of the delivered work depends on how it was built, and partner workshops confirm it item by item.
• A mock-up is not evidence of fire or strength. One built for look and fit may not use the tested composite or the classified board, so it cannot stand in for test reports. Keep those on the fire documentation file.

[Maker] is to build [a full-size prototype of item [ref] / a mock-up of [element or room]] to drawing [number, revision] and control samples [S-nn], from [production materials, hardware and finish], for approval before production of [the remaining [number] items] is released. The programme allows [n] working days to build, [n] for review and [n] for one re-presentation. Any difference from production materials is stated in writing before the review.

The review is a joint inspection by [designer], [client or operator representative], [maker] and [contractor], on [n] working days' notice. Criteria are in schedule [ref]: sizes within [clause ref]; finish to control sample [S-nn] under [named light] from [distance]; function as scored on [sheet ref]; hardware, interfaces, services and papers as drawn and scheduled; [brand standard ref]. Each group is recorded Pass, Conditional or Fail, with the name of the person who signs it. Photographs with a scale are filed with the record.

Production is not to start until [designer] has signed the record as Pass, or as Conditional with each condition closed in writing. Verbal approval is not approval. The approval covers drawing revision [letter] and items [refs] only. A later change is made only by written variation approved by [designer], stating its effect on programme and the contract sum, and substitution register [ref] is updated.

The approved mock-up is tagged, photographed and kept by [maker] as the benchmark until [practical completion]. It [is / is not] to be installed on site. [If installed: it meets the same specification and evidence requirements as production items, confirmed before the review.] It is not evidence of fire, strength or other compliance, which is shown by the documents in schedule [ref].

Standards and sources

• RIBA Plan of Work 2020 Overview (RIBA, 2020): read 5 Nov 2026; Stage 4 and Stage 5 text, paraphrased. It does not name prototypes or mock-ups for furniture or joinery.
• Designing Buildings: Samples and mock-ups for construction: commentary, last edited 24 Jan 2022; about construction products, used by analogy.
• Hospitality Net: hospitality consultant opinion piece (12 Dec 2024): commentary: build model rooms early.
• Make Bespoke Studio: Design development; How we work: prototypes for complex or high-value commissions.

Questions we are asked

Does every job get a prototype or mock-up?

No. In our process prototypes and finish mock-ups are available for complex or high-value commissions, and simpler items can go to production after sample approval. Say in the specification which items need one, and agree it with the maker early, because it adds a hold point to the programme.

What is the difference between a prototype, a mock-up and a first article?

A prototype is usually a full-size working example of one item. A mock-up is a full-size or part-size representation of an element or a room, built to judge appearance and fit. A first article is the first piece off the production run, checked against the drawing and the control sample. The words overlap, so agree what each one means on your project and write it into the approval note.

Who should attend a mock-up review?

The designer, the client or operator’s representative, the maker and, where the item meets a building, the contractor, plus anyone who owns services, lighting or the fire papers. Record names, not only job titles, and have one named person sign for each group of checks.

What tolerance should a mock-up meet?

The one in your specification. This sheet gives no figure, because there is no general number and one supplier’s example is not a standard. Write the tolerance in the specification, with the measuring method, using the joinery or furniture tolerance sheets as a starting point.

What if the mock-up fails?

Production is not released. The record says which groups failed and why, the maker amends or rebuilds, and the mock-up is presented again. Allow time in the programme for one repeat, and agree who bears the cost of a repeat before the first build, in the tender.

Can the mock-up room be used in the finished hotel?

Only if it was built to production standard and everyone agreed beforehand, in writing. Otherwise it is a benchmark that is kept and then returned or scrapped. A mock-up built for look and fit is also not evidence of fire performance or strength, which comes from the test reports for the real construction.

How long does a mock-up take?

It depends on the item and the maker, so this sheet gives no duration. Ask the maker for the build time and the review time, put both in the programme, and leave room for one repeat.