A system walkdown is a physical inspection of a complete commissioning system or subsystem, walked end to end against marked-up drawings, to confirm that what has been built matches the design and that it is ready for the next certificate. It is usually a joint walkdown attended by construction, completions, commissioning and the client, and its output is a categorised punch list. Before mechanical completion, it is the last chance to find construction defects while the system is still de-energised and the construction crews are still on site.
A good walkdown finds the things paperwork cannot: the valve installed back to front, the support that was never welded, the cable tray that blocks access to an isolation point. A bad one is a stroll through the plant that produces a list nobody trusts.
What is the purpose of a commissioning walkdown?
A walkdown before mechanical completion (MC) has four objectives:
- Confirm scope. Every tag in the subsystem is physically present, correctly tagged and installed where the drawings say it should be.
- Confirm conformance. The installation matches the latest approved P&IDs, isometrics, single lines and layouts, including items like flow direction, orientation, supports, drains, vents and access.
- Find defects. Anything incomplete, damaged or not to specification is recorded as a punch item and categorised.
- Agree readiness. The parties leave with a shared view of what must be fixed before the MCC is signed, and what can be carried forward.
Walkdowns are also used at other points: before ready for commissioning, before ready for start-up, and before handover. The pre-MC walkdown is typically the most detailed, because it is where construction defects are cheapest to fix. For how MC itself is defined and certified, see mechanical completion explained.
Who attends a joint walkdown?
A joint walkdown works because each discipline sees different things. Typical attendees:
| Role | Why they are there |
|---|---|
| Completions engineer (walkdown lead) | Organises the walk, holds the drawings and punch list, records items |
| Construction supervisor for each discipline | Answers questions, accepts actions, knows what is still in progress |
| Commissioning engineer for the system | Looks at the system as something that will be flushed, tested and run |
| Client or owner representative | Accepts categorisation and, eventually, the certificate |
| QA/QC inspector | Checks conformance to specification and inspection records |
| Operations representative | Checks operability, access, isolation points and maintainability |
| HSE representative (where required) | Looks at access, escape routes, guarding and safety equipment |
Keep the group workable. Five to eight people is usually enough; larger groups split into discipline teams walking the same subsystem, then reconvene to agree categories. Operations involvement is worth fighting for: operators spot problems with access, valve reach and isolation that engineers routinely miss, and it is far cheaper to fix them now than after handover.
How to prepare for a system walkdown
Most of the value of a walkdown is decided before anyone puts on boots.
Define the scope
Confirm the subsystem boundary and the list of tags in it from the tag register. If the tag register and the marked-up drawings disagree, resolve that first; otherwise you will be arguing about scope in the field.
Prepare the drawing set
Print or load the current revision of the drawings that cover the subsystem, marked up with the system boundary:
- P&IDs with the subsystem highlighted and boundary points marked
- Isometrics for piping, with test pack references
- Single-line and schematic diagrams for electrical scope
- Layout and plot plans so the team can find things
- Instrument location and hook-up drawings
Pull the status reports
Bring the current ITR status for the subsystem, showing which A-type records are open, and the existing punch list. Walking a subsystem where half the ITRs are still open is a construction progress check, not a readiness walkdown. A common rule is to walk only when A-ITRs are substantially complete and construction has declared the subsystem ready.
Agree the rules
Before the walk, agree the punch categories and who has authority to set them, how items will be recorded, and what the timeline is for the resulting punch list. Our guide to punch list categories A, B and C covers the common conventions.
Sort out access and safety
Walkdowns often happen in live construction areas. Arrange permits, scaffold access and escorts, confirm PPE, and check whether any part of the system has already been handed to commissioning control, in which case its access rules apply.
Walkdown checklist
Specific checks depend on discipline, but a general walkdown checklist includes:
- Every tag present, correctly identified and matching the register
- Equipment set, levelled, grouted and bolted down; guards fitted
- Valves installed in the correct orientation with handwheels accessible
- Flow direction correct on check valves, strainers and flow elements
- Pipe supports, guides and anchors installed as per isometrics; no temporary supports left in place
- Vents, drains and high/low points as per P&ID
- Temporary blinds, spools and test equipment identified and logged
- Cables installed, supported, glanded and terminated; cable markers fitted
- Earthing and bonding complete
- Instruments installed, impulse lines supported and correctly sloped
- Insulation, painting and fireproofing complete or recorded as agreed exceptions
- Access, escape routes and clearance for operation and maintenance
- Safety equipment such as eyewash, signage and relief devices installed
- Area clean and free of construction debris
Detailed discipline checks belong in the ITRs themselves; checksheets.com has discipline-specific inspection checklists if you need them.
Running the walk
- Brief at the start. Five minutes to confirm scope, route, categories, safety and roles.
- Walk in a logical order. Follow the process or electrical flow, from source to end user, rather than wandering the area. Mark each section on the drawing as walked.
- Record every item immediately. One defect per item, with tag number, precise location, description and a photo that shows the tag or a recognisable reference.
- Categorise on the spot. Agree the category while everyone is looking at the defect. Disputes get harder, not easier, back in the office.
- Assign an action party. Name the contractor or discipline responsible before moving on.
- Note boundary items. Anything at the subsystem boundary, such as tie-ins, isolation valves and spades, should be checked and recorded against the correct subsystem.
- Close with a debrief. Review the list, confirm categories and agree target dates for Category A items.
On the day, the most common failure is recording items vaguely. "Check supports" or "insulation incomplete" cannot be actioned or verified. Write each item so a stranger could find and fix it.
Capturing punch items with photos
Photos turn a disputed punch item into a clear one. Good walkdown photos:
- Show the tag plate or a reference in frame, or are taken as a pair: one close-up of the defect, one wider shot for context
- Are attached to the specific punch item, not dumped in a shared folder
- Are taken again from the same position at close-out, so the fix is visibly verified
Capturing items directly on a tablet or phone during the walk avoids the transcription step, which is where descriptions get shortened and tag numbers get mistyped. Offline capability matters here: plant rooms, modules and basements often have no signal.
Closing out after the walkdown
The walkdown is not finished when the group leaves the field.
- Issue the punch list the same day or next morning, grouped by action party and category.
- Work Category A items first, as they block the MCC.
- Verify on site. The originator or a nominated verifier checks each fix before it is closed. Items closed on the say-so of the action party alone have a habit of reappearing.
- Re-walk if needed. For subsystems with many A items, a short follow-up walk focused on those items is often faster than verifying them one by one.
- Attach the walkdown record and the resulting punch list to the MC documentation for the subsystem.
Running walkdowns in Accord and SnaggingTrack
In Accord, walkdown punch items are raised against the system and tag hierarchy, carry Category A/B/C criticality, and block the relevant certificates in the enforced dependency chain until cleared. ITR status and existing punch for the subsystem are visible before the walk, and readiness dashboards show what remains afterwards.
SnaggingTrack suits teams who want a field-first punch tool: it works fully offline and syncs when you reconnect, attaches photo, video and document evidence to every item, and lets you configure your own statuses, forms and verify-before-close workflow.
Frequently asked questions
What is the difference between a system walkdown and a punch walkdown?
The terms are often used interchangeably. Where they are distinguished, a system walkdown is the formal, joint inspection of a whole system against drawings to confirm readiness for a certificate, while a punch walkdown is a narrower walk to raise or verify punch items, often by a smaller team.
How long does a system walkdown take?
It depends on the size and complexity of the subsystem and how many disciplines are involved. A small utility subsystem may take an hour or two; a large process subsystem may take several sessions. Splitting large subsystems into sections walked by discipline teams keeps each session focused.
Should operations attend walkdowns before mechanical completion?
Where possible, yes. Operators are the people who will isolate, drain and maintain the equipment, and they often spot access and operability problems that designers and constructors miss. Raising those issues at MC costs much less than changing things after start-up.
What if the walkdown finds a design error rather than a construction defect?
Record it, but route it through the project's technical query or change process rather than treating it as a normal punch item. The construction contractor cannot fix a design issue on its own, and the item may need engineering, procurement and a revised drawing before it can be closed.
Can a walkdown be done remotely using photos or video?
Remote review can support a walkdown, for example to involve a specialist who cannot travel, but it does not replace a physical walk. Many defects, such as loose supports, poor access or missing items outside the camera's view, are only obvious in person.