Principal Contractor Advisory Support

Need a Competent Health & Safety Advisor for Your CDM Project?

Practical CDM support for Principal Contractors — advice, documentation, and structured systems to help you run organised, compliant projects.

If you’re managing the Principal Contractor role alongside running the job, we provide the expert guidance and support that keeps your Construction Phase Plan, RAMS, and site records properly organised and ready when clients or auditors ask to see them.

Experienced construction safety advisors supporting SME Principal Contractors across the UK.

37 Critical document templates for Principal Contractors: User Manual Index

Purpose and outcome (what “good” looks like)

The Services Isolation & Lock Off Register is your site’s single source of truth for what services have been isolated, how they were secured, who holds the locks/keys, and what checks were done before and after the work.

A good register is:

Current: it matches what’s happening on site right now (not yesterday).
Clear: anyone can quickly see what is isolated and what is live.
Controlled: lock IDs, tag IDs, and authorised removers are recorded—no “mystery locks”.
Closed out properly: reinstatement is signed off before anything is made live/pressurised again.

Who uses it (roles and responsibilities)

Role	What they do
Register owner (site)	Keeps the register updated, readable, and available. Leads handovers using the register.
Supervisor / Foreman	Checks isolations are planned, linked to permits/RAMS, and briefed to the team. Confirms entries are raised before work starts.
Authorised person(s)	Applies isolations/locks/tags, completes “test for dead/zero energy”, and (where authorised) removes locks and signs reinstatement.
Operatives / subcontractors	Check the register before intrusive work, follow the isolation controls, and report changes/issues immediately.
Principal Contractor / Client rep (if applicable)	May require evidence that isolations are controlled (register + permits + sign-offs). May need notifying before reinstatement.

Rule of thumb: the person doing the isolation records it, but the register owner makes sure it stays correct and complete.

When to use it (workflow triggers)

Before intrusive works: drilling, cutting, coring, chasing, breaking out, opening distribution boards/panels, lifting ceilings/floors.
Before demolition/strip-out: soft strip, partial demo, removal of plant/services, opening risers/ducts.
Before commissioning and testing: energisation, pressure testing, flushing, live testing, proving rotation, functional tests.
When changing temporary services: temporary power boards, bypass lines, temporary water, generators.
At shift change / weekly start / handover: review the live isolations so everyone knows what’s safe and what’s not.

Use it alongside permits (hot works, confined space, excavation, intrusive works). If a permit needs an isolation, the isolation must appear in the register.

Before you start (information and evidence you need)

Scope of work: what you’re doing, where, and what could be affected.
Service information: drawings, service plans, O&M info, labels, schedules, and any known isolation points.
Walkdown: confirm the actual isolation point on site (don’t rely on a memory or an old sketch).
Permit/RAMS references: permit number or RAMS/task brief reference that requires the isolation.
Lock-off kit: locks, tags, hasps, lock box (if used), and a way to uniquely identify each lock/tag (IDs).
Test equipment (where relevant): for electrical “test for dead” or other energy checks (pressure gauges, bleed points, indicator lights, etc.).
Authorised persons list: confirm who is allowed to apply/remove locks and sign reinstatement for that service.

⚠️ If you can’t identify the correct isolation point with confidence: stop and get the right help (competent electrician, gas engineer, building engineer, the PC/client).

How to complete it (step-by-step on a live site)

Step 1: Set up the register header (once per site / week)

Complete the project/site details so everyone knows which job and where the register is kept.
Write the register location (e.g., site office folder, permit board, digital PDF in the site drive).
Confirm who the register owner is for day-to-day control.

Step 2: Create one entry per isolation (live list)

When an isolation is needed, create a new reference (Ref) and fill in the “live list” details so someone can find it and understand it quickly:

Service: electrical, gas, water, compressed air, HVAC controls, alarms, fuel, etc.
Location/area: be specific (floor, room, riser, plant room, unit number).
Isolation point ID/description: e.g., “DB2 CB-14”, “Gas ECV by meter”, “Water valve V3 in riser”.
Method: breaker/MCB, valve, blank/flange, lockable isolator, key switch, lock box, etc.
Status: mark clearly as ISOLATED (or LIVE if you are recording known live constraints).
Date/time isolated: this matters for handovers and tracing.

Site tip: if multiple points are needed to make it safe (e.g., more than one circuit/valve), either list all points clearly in the entry or use separate refs—whatever keeps it unambiguous on your site.

Step 3: Record “test for dead / zero energy” (where required)

If the task requires proving isolation (common for electrical and stored energy systems), record:

What and where was tested: “Tested at outgoing terminals of isolator”, “Tested at equipment terminals”, “Bled pressure at drain point”.
Result: “Dead/Zero” or “N/A” (only use N/A when proving dead is not relevant).
Tested by: name/signature (must be competent for the system).
Permit/RAMS ref: link it back to the job control paperwork.
Notes: partial isolations, affected tenants, temporary supplies, unusual conditions.

⚠️ Important: “Switched off” is not the same as “isolated”. The register should show how it was made secure and how it was verified safe.

Step 4: Record locks and tags issued (control of keys)

For each isolation ref, record every lock/tag used:

Lock ID and tag ID: unique numbers/labels.
Issued to: who the lock/tag is assigned to (name).
Key held by: who physically has the key (or lock box reference if used).
Authorised to remove: the named person(s) allowed to remove that lock.
Date/time issued: helps control handovers and close-out.

Good control: if someone goes off-site, their lock stays on unless the exception process is followed and recorded.

Step 5: Keep it current during the work

At start of shift and after breaks, confirm the isolation is still in place if the job relies on it.
If anything changes (scope, location, additional circuits/valves found), update the register straight away and re-brief.
Use the register at handover: read out the live isolations and any restrictions.

Step 6: Reinstatement (making live again) and closing the entry

Before removing locks/tags and reinstating:

Complete the checks before reinstatement (work complete, guards back on, access panels fitted, area clear, leaks checked, warnings updated/removed).
Confirm affected people have been told (occupiers, other trades, PC/client, neighbours if relevant).
Locks/tags are removed only by authorised persons as recorded.
Record reinstated and tested (what was tested and results).
Close the entry: sign-off name/signature and date/time closed, and close any related permit.

Practical check: if you can’t explain in one sentence what was reinstated and what proof you have it’s safe, the close-out is probably not complete.

Review and approval (who signs and what they check)

Isolation applied: completed/confirmed by an authorised person for that service.
Test for dead / zero energy: signed by the competent tester (often the authorised person).
Locks/tags control: checked by the register owner/supervisor (IDs, key control, authorised removers named).
Reinstatement: signed off by an authorised sign-off person before the system is made live/pressurised.

Escalate to site management/PC/client rep when:

the isolation affects building occupants, neighbours, shared systems, or critical services (fire alarms, medical gases, security);
you find unexpected backfeeds, cross-connections, or you cannot prove isolation;
someone requests reinstatement before the checks are complete;
there is any need to use the exception process for removing someone else’s lock.

Recordkeeping (where to keep it, version control, retention)

Location on site: keep the live register where people actually look—commonly the permit station/board or the site office safety folder.
Single live copy: avoid multiple competing versions. If you use digital, make sure there is one controlled file and a clear “current” printout if needed.
Attach supporting evidence: link or file permits, RAMS, commissioning sheets, and any test records alongside the register references.
Retention: keep the register with the job file at least until handover/completion, and longer if your company/PC/client requires it (treat it like permit and safety records).
Audit readiness: entries should show a clear story: planned → isolated → proved safe → controlled locks → reinstated → closed.

How often to review/update

Immediately when an isolation is applied, changed, extended, or removed.
Daily: review at the start of shift and during handover (especially if multiple trades are working).
Weekly: quick housekeeping check—remove closed items from the “live focus” and ensure any long-running isolations still have a valid reason and controls.
Before commissioning/energisation days: do a focused review with the team (what will become live and in what order).

Common mistakes (and how to avoid them)

Mistake: Isolation recorded vaguely (“main switch”, “valve in riser”).
Fix: Use specific IDs/locations and add a short description someone else can find.
Mistake: Register filled in after the job starts.
Fix: Make the entry part of the permit/task brief: no register entry, no intrusive work.
Mistake: No “test for dead/zero energy” recorded (or “N/A” used when it shouldn’t be).
Fix: Record what was tested, where, by who, and the result. If it can’t be proved, stop and escalate.
Mistake: Locks/tags not traceable (no IDs, no owner, keys floating around).
Fix: Treat lock IDs like tool control—every lock/tag recorded, and keys controlled.
Mistake: Someone removes another person’s lock “to help”.
Fix: Only authorised removers. If the lock owner is unavailable, use the exception process and document it.
Mistake: Reinstatement happens without warning, affecting other trades/occupiers.
Fix: Notify affected people, then sign off reinstatement checks before making live.
Mistake: Old isolations left open in the register and nobody knows what’s still isolated.
Fix: Daily review at handover; close entries properly and keep the live list clean.

Worked scenario (realistic example)

Job: Core drilling through a wall in a plant room to install new pipework. There are existing electrical supplies and a water main nearby.

Plan: Supervisor reviews RAMS and raises an intrusive works permit. Drawings show a nearby local isolator feeding a pump panel.
Identify: Authorised electrician confirms the correct isolation point: “Panel P1 isolator” and checks for any backfeed.
Isolate + lock/tag: Electrician isolates at P1, fits a lock and tag with recorded IDs, and notes the area affected.
Prove dead: Electrician tests at the equipment terminals, records “Dead/Zero”, signs, and links the permit reference.
Work proceeds: Team cores the wall. During the day a second circuit is found feeding a local socket—work stops, a second isolation ref is added, and the team is re-briefed.
Reinstate: After drilling and making good, the supervisor completes the reinstatement checks (guards back, area clear, no leaks, people told). The authorised person removes locks, energises, tests operation, records results, and closes the register entries and the permit.

Principal Contractor Support

Running a CDM Project as Principal Contractor?

Get the structure, advice, and documentation support you need to manage the role properly.

When you take on the Principal Contractor role, the responsibility for the Construction Phase Plan, site safety records, RAMS, and CDM compliance usually lands on the desk of a busy director or site manager.

CTC South West provides practical advisory support and structured systems that help you keep your documentation organised, your responsibilities clear, and your projects ready for client checks or audits.

Expert CDM support, site-ready documentation, and organised compliance records — all built around how construction projects actually run.

Construction Phase Plans structured and ready for client review
RAMS and project documentation tailored to your actual work
Ongoing competent person support for Principal Contractors

Practical advice from experienced construction safety advisors — supporting SME Principal Contractors across the UK.