Design freeze in offsite construction
A design freeze is the date after which the design is locked so factory production can start. In offsite construction, changes after that date cost more than changes before it.
In conventional building, many decisions can wait for site conditions. In offsite construction, the factory needs drawings that are complete enough to cut, assemble, finish and ship against. The design freeze is the formal moment you accept that the design is final for production. The glossary entry gives the short definition; this page covers how to run one.
Why it matters more offsite
- Components may be ordered and fabricated well before they are installed.
- Factory slots are planned around released drawings.
- Repeated units multiply the effect of a change.
- Interfaces with foundations and utilities have to match what the factory builds.
What should be settled before freeze
| Area | Examples to settle |
|---|---|
| Architecture | Layouts, dimensions, openings, finishes schedule |
| Structure | Engineer's design, connections, bracing, load paths |
| Services | Routes, penetrations, panel positions, fixture locations |
| Envelope | Layers, joints, products (coordination guide) |
| Interfaces | Foundation, utilities, adjoining structure (foundation interfaces) |
| Approvals | Permit or authority acceptance of the design |
Building a sensible freeze process
- Create a pre-freeze checklist per discipline, and have each discipline lead confirm in writing.
- Hold a review where the factory challenges the design for buildability. See design for manufacture and assembly and constructability.
- Issue a numbered, dated set of drawings and specifications as the freeze set.
- Have the owner or authorized representative sign the freeze.
- Start production only against the freeze set.
The earlier handoffs between design and delivery are covered in design-to-delivery handoffs.
Handling changes after freeze
Agree the change process before signing the contract. Each request should state what is changing, why, the cost effect, the schedule effect and who approves. Record it in a change-order log. Quote the supplier's stated cost and time; do not assume numbers. Structural or compliance-related changes need review by the engineer of record and the local authority.
What to do when the owner is not ready
- Decide which items can be flexible without affecting the factory scope, such as site-installed finishes.
- Postpone freeze rather than freeze an incomplete design; delay is usually cheaper than rework, but confirm with the supplier.
- Identify long-lead items that could be released early with limited risk (long-lead planning).
Phased projects
For multiple phases, freeze a reference design for the repeating elements and treat deviations as changes. See phased developments. The schedule consequences are laid out in the modular timeline template, where the freeze date is one of the most important milestones to make explicit.
Questions people ask
What is a design freeze?
A formal point at which drawings and specifications are fixed for production. Changes afterwards go through a controlled process.
Why does offsite construction need one?
Factories build to released drawings and order materials against them, so late changes affect production and supply.
What should be frozen?
Layouts, dimensions, structural design, services routes, openings, finishes and the interfaces with site works.
Can anything change after freeze?
Yes, through a documented change request with time and cost stated before approval.
Sources and further reading
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