Gateway 2 and the Golden Thread for Building Services Engineers
What services engineers evidence for higher-risk buildings, how change is controlled after approval and what the golden thread needs from the services record
On a higher-risk building, building services are where much of the life safety design sits: fire detection, smoke control, sprinklers, the penetrations through compartment lines, the riser that carries them. Gateway 2 asks for the reasoning, and the golden thread asks for the evidence to be kept and kept current. This guide sets out what services engineers contribute to a Gateway 2 submission, what changes after approval, and what a services record needs to contain by completion.
Services evidence is produced for approval, protected by change control during construction and completed with as-built records at handover.
What does Gateway 2 ask of a building services engineer?
Gateway 2 is building control approval from the Building Safety Regulator for a higher-risk building. Services engineers contribute the design basis and compliance reasoning for the systems they design, mainly through the compliance statement, fire and emergency file and drawings.
The guidance on preparing information for a building control approval application says that a higher-risk building is one that has at least 7 storeys or is at least 18 metres high, and has at least 2 residential units or is a hospital or a care home. The Building Safety Regulator oversees and approves building work for these buildings, and the application for building control approval is Gateway 2. Work must not start until approval is given. The guidance applies to England. The higher-risk buildings guide covers scope, and the Gateway 2 submissions guide covers the application as a whole.
Services engineers are rarely the applicant. The client makes the application, with a principal designer and principal contractor named. The services engineer's contribution is the design information and reasoning that sits inside several of the documents the guidance lists.
- Building regulations compliance statement
- For each element, how the planned work meets the relevant functional requirements, which guidance, standards or design codes are followed, why they were chosen and why following them means the work will comply.
- Fire and emergency file
- The fire strategy in plans and text: means of escape and warning, internal and external fire spread, fire service access, and how the building is to be managed and maintained so it can be evacuated.
- Drawings and plans
- The drawings that describe the project and show how the work complies, labelled and referenced from the application.
- Construction control plan
- The strategies, policies and procedures to make sure the work meets the regulations, that people are competent, that designers and contractors share information, and how as-built evidence is captured.
- Change control plan
- How all changes will be managed and recorded, who decides, how advice is recorded and how notifiable and major changes are identified.
- Mandatory occurrence reporting plan
- The systems for reporting building safety incidents or risks involving structural failure or the spread of fire or smoke.
The services engineer rarely writes these documents alone, and each one relies on the services design being stated clearly enough to be reasoned about.
The compliance statement is where the services engineer's reasoning is most exposed. The guidance requires the applicant to say which guidance or standard was followed, why it was chosen and how following it shows compliance. For a services system, that means an engineer's reason for the design basis, for example why a particular smoke control approach suits this building, not just a citation of the standard.
What must services engineers evidence for each life safety system?
For each fire safety system the engineer evidences a design basis at Gateway 2 and as-built proof at completion. The fire strategy defines which systems the approved design relies on.
The list below covers the systems that most often carry the life safety case on a higher-risk building. Which ones apply, and to what standard, is set by the fire strategy and the fire and emergency file for the project.
- 01
Fire detection and alarm
Category, extent, cause and effect, interfaces with other life safety systems, and the edition of the code of practice relied on.
- At Gateway 2
- Design basis and category, to the edition cited. BSI lists BS 5839-1:2025 as current
- At completion
- Design, installation and commissioning records and certification
- 02
Smoke control
Strategy, extent, activation logic, supplies and the design standard named in the fire strategy.
- At Gateway 2
- Strategy extract, design criteria and reasoning
- At completion
- Calculations, commissioning and witnessed test records
- 03
Sprinklers and suppression
Design basis, hazard or occupancy class, water supplies and the standard followed. Name the standard and edition given in the fire strategy.
- At Gateway 2
- Design basis, extent and supplies
- At completion
- Installation and commissioning certificates, as-built drawings
- 04
Penetrations and compartmentation
Where ducts, pipes and cables pass through compartment walls and floors, how each opening is protected, and by whom.
- At Gateway 2
- Strategy and tested details, with openings shown on drawings
- At completion
- Installation records and evidence for each opening
- 05
Protected shafts and risers
Which services may run in a protected shaft, how the shaft is closed at each floor, and access arrangements.
- At Gateway 2
- Shaft strategy and services allocation
- At completion
- As-built riser drawings and inspection records
- 06
Life safety power and supplies
Supplies that keep life safety systems running, with the resilience the fire strategy requires.
- At Gateway 2
- Supply strategy and design basis
- At completion
- Test records and certification
The right-hand entries are a guide. The fire strategy and the approved documents decide what the project is held to.
Make the specification say what the evidence must be
The simplest way to be ready for completion is to ask for the evidence in the specification. A clause for each life safety system should state the standard and edition, the design inputs, the submissions before manufacture, the tests with their acceptance criteria and witnessing, and the records to be filed on completion. The fire alarm specification guide and the commissioning and O&M specification guide cover the clause content. For each clause, there should be a row in the design responsibility matrix that says who designs the system and who reviews the returns.
Openings and fire stopping deserve their own line
Guidance from the Building Safety Regulator lists the number or dimensions of any openings in a wall, ceiling or other building element for any pipe, duct or cable as a notifiable change. That makes the services penetration schedule a controlled document in its own right. Name one owner for it, tie each opening to a fire stopping detail and a record, and make sure the specification and the drawings use the same opening references.
How is competence evidenced for services designers?
The client declares that the principal designer and principal contractor are competent, the construction control plan must show that those working on the project are competent, and designers carry duties under Part 2A. Services practices should be ready to name and evidence the people leading each life safety system.
Competence appears in three places in the application. The client signs a competence declaration confirming that it has taken all reasonable steps to check that the principal designer and principal contractor are competent to carry out their duties, and that it has asked those working on the project whether they have been issued with a serious sanction in the last 5 years. The construction control plan must describe how the project will make sure that those working on it are competent to carry out the work they are contracted to do and have enough information and training. And Part 2A of the Building Regulations 2010 puts duties on designers, including planning, managing and monitoring design work, under regulations 11J and 11K inserted by SI 2023/911. Part 2A duty holders and the principal designer duties guide set out the allocation.
For a services practice, the practical point is that the client and principal designer will ask for evidence of who is doing the work and why they are suited to it. Be ready to name the lead engineer for each life safety system, the professional registration and relevant experience they hold, and the review route inside the practice. Check the current Building Safety Regulator guidance on how individual designer competence is evidenced.
Keep competence connected to the matrix
The simplest way to avoid a gap between the competence statement and the design is to add the named lead to each life safety row of the responsibility matrix, and to record who reviewed each contractor-designed portion. Where the contractor completes a design, the specification should require the contractor to name the designer and state their competence, and the review process should record that the information was received.
What happens when a services design changes after approval?
Any change to the agreed documents is a controlled change, classified as recordable, notifiable or major. Openings for pipes, ducts and cables are a named notifiable change, and changes to active or passive fire safety measures in the fire and emergency file are major.
Once the Building Safety Regulator has approved the application, the documents uploaded become the agreed documents. Any change to them is a controlled change. Each change must be managed and assessed according to the change control plan and recorded in the change control log. The principal contractor creates and maintains the log, and the principal designer and principal contractor identify and assess the effect of changes. For services, change is constant: products are substituted, routes move, a plant selection changes after a late coordination clash. The question each time is which category the change falls into.
Scroll horizontally to view all columns.
| Services change (illustrative) | Likely category | What follows |
|---|---|---|
| Replace a fire damper with another of the same or higher classification | Recordable: the guidance treats a replacement of the same or higher specification or class as recordable | Record in the change control log with reason, advice and affected documents |
| Change the number or dimensions of openings for pipes, ducts or cables | Notifiable: named in the guidance | Notify the Building Safety Regulator before the change is carried out or related work starts |
| Substitute a product with a different reaction to fire classification, even a higher one | May be notifiable | Assess against the agreed documents and the change control plan, then notify if required |
| Substitute a product with a lower reaction to fire classification than the application specified | Major | Stop related work, apply and wait for approval |
| Change any part of the active or passive fire safety measures in the fire and emergency file, such as smoke control or sprinkler arrangements | Major | Stop related work, apply and wait for approval |
| Change a design assumption stated in the building regulations compliance statement | Major | Stop related work, apply and wait for approval |
The classification of any real change depends on the agreed documents and the project's change control plan. Confirm with the principal designer and, where in doubt, the Building Safety Regulator.
Gov.uk guidance says that for a major change the work relating to it must stop, an application must be submitted and approval obtained before the work proceeds, and that the regulator will take up to 6 weeks to assess a major change application unless an extension is agreed. That is a programme risk for services work, which often changes late. A change that looks like a product substitution can be a major change if it touches a fire safety measure described in the fire and emergency file.
What services engineers should do differently
Build the change question into the services workflow. Before an RFI response, a substitution approval or a revised drawing goes out, ask whether it changes an agreed document and, if so, which category it is. Copy the principal designer into the response. Keep the reason and the advice taken, because the log must record who advised and what they said, even if the advice was not followed. Specification change control sets out the document-side method.
What does the golden thread need from the services record?
The services record should show, for each life safety system, the requirement, design, review, change, proof and handover, kept digitally with version control and handed to the person who will manage the building.
The golden thread guidance says that clients, principal designers and principal contractors on a higher-risk building project must keep a digital record of information about the building. The record must be kept digitally, secure from unauthorised access, available when needed, usable, a single source of truth and accessible. The client provides a record-keeping system with version control. The principal designer must capture and keep the design information up to date and work with the principal contractor to record and evidence design work during construction. The principal contractor must use the client's system, keep evidence that the work meets building regulations and work with the design team to manage controlled changes.
What the services record needs to show
- Requirement. The specification clause states the standard, edition, design inputs and evidence required.
- Design. The design information, calculations and drawings, with the version and author.
- Review. The reviewer's comments and the submission status.
- Change. Any change since approval, with category, reason and advice taken.
- Proof. Test, commissioning and certification records against the clause.
- Handover. As-built information, O&M and log book content, delivered to the person who will manage the building.
Each step should be filed against the clause it relates to, in the project's record-keeping system, so that a reviewer can walk the thread in either direction.
At completion, the client applies for a completion certificate and must demonstrate that the building information has been handed to the accountable person or the Responsible Person. The guidance lists what must be handed over, including the information used for the approval application, the information provided for the completion certificate application and the relevant fire safety information. The change control log is submitted with the completion certificate application. For services this means that O&M manuals, commissioning records and as-built drawings are part of the statutory record, not a courtesy at handover.
Services-specific record content
A practical list of what the services record should hold by completion: the final design basis for each life safety system and the standard edition it was designed to; the schedule of penetrations with the protection used and evidence for each; commissioning and witnessed test records for fire alarm, smoke control and sprinklers; certification for the fire detection and alarm system, including design, installation and commissioning records as the code of practice requires; as-built drawings and schedules; O&M manuals; and the change control log entries that affect services. The commissioning, soft landings and O&M guide covers the specification of the handover content, and the golden thread guide covers the wider duty.
A closing check for the services engineer
- Every life safety system has a design basis, a standard and an edition, written down.
- Every life safety clause asks for the evidence that will be filed at completion.
- The penetration schedule has one owner and matches the drawings and the fire stopping details.
- Every change since approval has a category, a reason and a record of the advice taken.
- Each contractor-designed portion has a named designer and a reviewed set of returns.
- The O&M and commissioning content is specified, dated against the programme and filed against its clause.
Questions engineers ask about Gateway 2 and the golden thread
What do building services engineers need to evidence for Gateway 2?
For a higher-risk building in England, services engineers contribute the design basis and compliance reasoning for the systems they design, mainly through the building regulations compliance statement, the fire and emergency file, drawings, and the change and construction control plans. For each element the statement must say how the work meets the functional requirements, which guidance or standards are followed and why.
Which services count as fire safety systems for a higher-risk building?
Typically fire detection and alarm, smoke control, sprinklers and other suppression, fire dampers and fire stopping where services penetrate compartment lines, services in protected shafts and risers, and the power supplies that keep life safety systems running. The fire strategy and the fire and emergency file define exactly which systems the approved design relies on.
What happens if a services design changes after Gateway 2 approval?
Any change to the agreed documents is a controlled change and is recorded in the change control log. Notifiable changes must be notified to the Building Safety Regulator before the work starts, and major changes need its approval first. Changing the number or dimensions of openings for pipes, ducts or cables is a notifiable change, and changes to active or passive fire safety measures in the fire and emergency file are major.
How long does the Building Safety Regulator take to decide a major change?
Gov.uk guidance says the Building Safety Regulator will take up to 6 weeks to assess a major change application unless an extension is agreed. Building work related to the major change must stop and must not start until the change is approved.
What is the golden thread for building services?
It is the digital record of information about the building, kept during design and construction and handed over at completion. For services it includes the design information, calculations, specifications, change records, commissioning results and operation and maintenance information for the systems that keep the building safe, held with version control as a single source of truth.
Who is responsible for proving that services designers are competent?
The client signs a competence declaration confirming that it has taken reasonable steps to check that the principal designer and principal contractor are competent, and the construction control plan must show that those working on the project are competent and have enough information and training. Engineering practices should be ready to evidence the competence of the people they put forward.
Where Avoice fits
Gateway 2 is a documentation problem as much as a design problem: the reasoning exists, and the difficulty is keeping it connected to the specification that says the same thing.
Avoice's Compliance module supports Gateway 2 preparation and the golden thread, with registers for building regulations, CDM risk and principal designer duties, and a Project Record that holds the information behind them. Avoice now also writes building services specifications, so services clauses can sit in the same record as the architectural clauses they depend on. Construction Admin tracks submittals, RFIs and instructions against the specification, and spec change tracking records changes to requirements with a reason and a date. The pre-issue Technical Review compares the specification with schedules and drawings before the document goes out.
Software holds and connects the record. The engineer decides whether a change is recordable, notifiable or major, and the principal designer and principal contractor run the change control process the project has agreed with the Building Safety Regulator. For the architectural side of the same submission see Specification and Gateway 2 and the Gateway 2 submissions guide.