Change control after drawing sign-off

At a glance

Qualitative: what kind of cost falls where, not how much. The maker states the amount. Practice guidance, not a standard.

Where development ends and change control begins

Before drawings are signed, comments are development: the designer marks the shop drawings, the maker revises them and the designer reviews again. That loop is expected and is part of the price. After sign-off, the same comment is a change to something agreed, and it needs a different route. The RIBA Plan of Work 2020 draws the same line for building design: its glossary defines Change Control Procedures as the procedures for controlling changes to the design and construction after the Stage 2 Concept Design and the Project Brief are signed off, and says functional changes, such as moving a space or altering its size, are not design development and belong under change control. It also says the cost of change increases as the project moves through Stage 4 towards construction, because more design information needs updating, until a change affects work already under way on site (Figure 4 of the Plan). The Plan is about whole buildings and is not contractual, so we apply the idea by analogy: for a bespoke package the sign-off event is the approved shop drawings and the signed samples.

NBS says the same in plainer terms: a specification must be kept up to date and properly documented to track revisions, and the common mistake is not tracking and communicating changes, which can leave outdated or conflicting documents on site (Dr Stephen Hamil, 2 April 2025). A change that is agreed in conversation but never reaches the drawing is the commonest way the maker builds one version and the designer inspects another.

A design freeze is the date after which any change to the listed items needs a variation request. It is set backwards from the maker’s ordering dates and production slot, which in turn are set backwards from the date the room is ready (see the long-lead register), and it should be stated before drawings are signed, so that nobody meets it for the first time as a penalty.

What a change drags with it

The table at the top of the page lists seven stages. It describes where the cost and the delay fall, not how much they are, because the amount depends on the item, the material and the maker. This sheet gives no figures, and the figure that matters is the maker’s own, written in a revised quotation. Three things make a change dearer than it looks.

• The change drags other things with it. A new finish is a new sample and a new signature. A new board or fabric can mean a new fire test, a new certificate or a new warranty position. The substitution register lists what each kind of change puts back in question.
• The sunk cost is not the changed item’s alone. Material already bought, parts already cut and a production slot already held are lost or moved, and the slot can be lost for items that did not change if they share a run, a workshop or a delivery.
• Other trades move. A change to an opening, a service point, a light position or a floor level reaches the contractor, the electrician and the floor layer. The site readiness checklist shows how many things have to be ready in a given order.

A change that removes something can still cost, if the material is bought. And a late change is not always the designer’s: a survey that finds the wall out of true (see site survey and dimension verification) is also a change, raised by the site, and goes through the same form.

The variation request: one page

One page, one change, one number. The form below is a starting point; the fields and the reason for each are in the table.

• Anyone may raise a request. Only someone with authority may instruct it. Designing Buildings notes that a contract needs express terms giving the power to instruct a variation, and that standard forms generally give it to the contract administrator. Check who holds it under your contract.
• Put it in writing before work changes. A verbal instruction should be confirmed in writing before the maker acts on it. The maker should flag it if it is not.
• The maker answers before anyone decides. The response states the cost and time effect and what evidence has to be re-supplied. The designer and the client then decide with those figures in front of them.
• A change that touches a drawing makes a new revision. The superseded revision is marked superseded and the FF&E schedule is updated. Designing Buildings says variations from the design drawings should be highlighted on the shop drawings and brought to the design team’s attention, and that design-team review does not relieve the originator of the drawings of responsibility for them.
• A substitution that moves price or programme is also a variation. Log it on both: see the substitution register.

Our pricing page says that any variation requested after the quotation is approved is costed and approved in writing before work changes. Our project management page describes the same sequence: variations priced and programmed before they are made. This sheet describes that sequence in general terms and states no term of its own.

Asking for the cost and time effect

Ask the maker the same six questions each time. They are the fields in the maker’s response block.

1. What is affected? Which drawings, samples, materials and parts already made?
2. What can be reused, and what is lost?
3. What is the new date for this item, and does it move the date of any other item, any other trade or the installation sequence?
4. What evidence stops describing what you will receive? Tests, certificates, timber claims, EPDs, warranty terms and signed samples.
5. What does it cost, as a line in a revised quotation with its assumptions written down, and until when does the response stand?
6. What happens to the programme if no decision is made by [date]?

How a variation is valued depends on the contract. Designing Buildings reports that standard forms often value a variation from the contract’s own rates where the work is similar and on a fair valuation of cost, overheads and profit where it is not, and that NEC contracts assess compensation events on defined cost plus fee instead. It also says a variation may, but does not necessarily, justify more time. For a supply order outside a building contract the quotation’s own terms apply. Your contract adviser can say which applies, and should write it into the variation clause.

Setting and holding a design freeze

A freeze works when it is specific, early and written. Five steps:

1. List what is frozen. The items by code, with the drawing revision and sample reference for each.
2. Set the date from the maker’s dates, not from the designer’s. Ask the maker for the date by which long-lead materials must be ordered and the date a production slot starts, then work back from the date needed on site.
3. Tell the client in writing, before sign-off, what a change after the date means: a variation request, a cost and time effect, and possibly a lost slot.
4. Agree an exception route. Safety, a regulatory change and a site discovery are real reasons to change after the freeze. They go through the same form and are not refused by default.
5. Record it. The freeze date, the revision frozen and who signed go on the schedule and on the drawing register.

Leave a short list of things the maker may decide without a request, such as the order of assembly or concealed fixings of the same type and rating, and say so in the specification: the substitution register calls it the maker’s choice list. Everything not on the list is frozen.

The design of [package] is frozen on [date], meaning the approval of drawings [list, revision] and signed samples [list]. After that date a change to any item, dimension, material, finish, hardware or quantity shown on them is a variation, made only by written instruction under the clause below. The Supplier is to confirm by [date] the dates by which materials will be ordered and production will start, so that the freeze date can be checked against them.

A variation is requested on form [ref], numbered and dated, by [Designer / Employer / Supplier]. The Supplier is to respond within [ ] working days with: the drawings, samples and materials affected; the cost effect as a line in a revised quotation; the effect on the date for the item and on any other item, trade or the installation sequence; and any evidence to be re-supplied. The response stands for [ ] working days. The Supplier does not act on a variation until [named role] has instructed it in writing. A verbal instruction has no effect until confirmed in writing.

Work done on a change that has not been instructed in writing under this clause is at the risk of the party that did it. [Who bears the cost of removal and remake to be agreed with the contract adviser.] Each approved variation is entered on register [ref] and issued as a new drawing revision [letter] and, where it affects the FF&E schedule, schedule revision [ ]; the superseded revision is marked superseded.

Standards and sources

• RIBA Plan of Work 2020 Overview: Change Control Procedures; Figure 4: PDF p.124; read.
• NBS: Five essential tips for writing effective specifications (2 Apr 2025): tip 5.
• Designing Buildings: Variations in construction contracts; Shop drawings: edited 19 Aug 2026 and 9 Aug 2022; commentary.
• Make Bespoke Studio: Pricing; Project management: live statements repeated.

Questions we are asked

Can I change something after the shop drawings are approved?

Yes, but by a written variation request, not a conversation. The maker states what the change does to cost, to time and to the evidence behind the item, and the designer and client decide with those figures. Comments made before approval are development, not variations.

Does a change always cost more?

Not always, but it often does, and the later it comes the more there is to undo. A change that removes something can still cost if the material has been bought. The amount depends on the item and the maker, so ask for it in writing; this sheet gives no figures.

What is a design freeze?

The date after which any change to the listed items needs a variation request. It is set backwards from the maker’s ordering dates and production slot, stated before drawings are signed, and recorded against the drawing revision.

Who pays for a late change?

The contract decides, and a variation is normally priced before it is instructed. Ask for the maker’s figure first. How a variation is valued, and whether it justifies more time, depends on the contract form.

What should a variation request include?

A reference, the item codes, the drawing and sample references with their revisions, the change from and to, the reason, the stage reached, then the maker’s cost effect, time effect, evidence affected and the length of time the response stands, and the decision and instruction.

What is the difference between a variation and a substitution?

A substitution is a change to what is specified, and the substitution register records it. A variation is the written instruction that changes price or programme. A substitution that moves either is also a variation.

What if the site, not the design, changes?

A survey that finds a wall out of true, or a service in the way, is a change raised by the site. It goes through the same form, with the survey record attached.