Overview
Cable trays and trunking create complex penetrations:
- multiple cables
- changing occupancy over time
- irregular gaps that are hard to “patch” properly
That’s why containment routes are frequently flagged in compartmentation surveys.
Why containment penetrations are a repeat-defect hotspot
Containment is different to a single pipe or cable:
- mixed services (data, power, alarms, controls) change over time
- cables are often added quickly during fit-outs and upgrades
- trays and trunking create long, awkward gaps (including above and behind runs)
That combination is why you often see the same risers and corridors repeatedly flagged on surveys.
Where to look first (if you’re triaging a site)
If you’re trying to find the highest-likelihood defects quickly, start with:
- risers serving multiple floors
- plant areas where containment is dense
- corridor ceiling voids where trays pass through compartment lines
- IT/comms rooms with frequent change
- any area with recent refurbishments (kitchens, bathrooms, fit-outs)
These are the places where “it was fine last year” becomes “it’s open again this year”.
What “good” looks like in plain terms
A durable approach usually has three ingredients:
- A stable reference (defect ID + location that won’t change)
- A tested system approach (not “just foam it”) appropriate for the substrate and service mix
- Close-out evidence so future trades can reinstate correctly after changes
If any of these is missing, defects tend to come back.
Simple priority guide (table)
| Priority | Typical scenario | Why |
|---|---|---|
| P1 | open voids on protected routes (stair/lobby), or major breaches in risers | higher life-safety exposure |
| P2 | incomplete seals, damaged materials, one-face-only works | likely to fail audits and re-checks |
| P3 | minor tidy-up, documentation gaps where seal appears sound | improve governance and future maintenance |
Common defects
- open voids around trays or trunking
- ad hoc foam/filler without proper system detail
- incomplete sealing at the rear or above tray runs
- later cables added without reinstating fire stopping
Typical defect patterns (table)
| What you see | Why it’s a problem | What a sensible fix usually involves |
|---|---|---|
| Open void around tray/trunking | smoke/fire can pass around the service | system-based sealing detail appropriate to the opening |
| Foam used as the only “fire stop” | generic foam often isn’t a tested fire stopping system | remove/replace with tested system; evidence the method |
| Fire stopping only on one face | breach can remain on the unseen side | check both faces where accessible; record constraints |
| Incomplete seal above tray | common “hidden gap” | inspection + sealing of the full perimeter |
| Later cables added through the seal | breaks the system continuity | change-control: reinstate after every modification |
Scoping remedials that survive follow-on works
The goal is not just to “make the photo look sealed” today — it’s to avoid rework six months later.
Step-by-step scoping (table)
| Step | What to do | Output |
|---|---|---|
| 1. Define the survey area | confirm risers/rooms/levels and which compartments are in scope | scope note + plan markup |
| 2. Create stable IDs | assign defect IDs linked to locations | defect register |
| 3. Record service mix | note cable types/volumes and any trunking | photos + notes |
| 4. Choose system types | select tested systems appropriate to substrate and opening | specification note |
| 5. Set evidence requirements | decide what photos/labels are required at close-out | close-out checklist |
| 6. Include change-control | set rules for reinstatement after cable additions | process note |
What to ask for in the close-out pack
Containment remedials are hard to defend later without a tidy evidence pack.
Close-out evidence checklist (table)
| Item | Why it matters |
|---|---|
| Defect register marked closed | proves what was completed |
| Photos (before/after) with defect ID visible | makes audits and re-checks possible |
| System reference / method statement summary | avoids “unknown material” later |
| Exceptions list (no access / constraints) | stops false confidence |
| Maintenance / change-control note | prevents re-opening during future works |
Simple change-control rule (so defects don’t reappear)
If cables are added or removed, you want one simple operational rule:
- No cable modifications through compartment lines without reinstatement and a recorded close-out.
In practice that can be as simple as:
- permit-to-work requirement for risers
- labelled “fire stopping zones” with instructions
- a named person/team responsible for reinstatement sign-off
A lightweight change-control workflow (table)
| Stage | What happens | Evidence |
|---|---|---|
| Before works | identify whether the route crosses a compartment line | permit / brief |
| During works | prevent ad hoc cable adds through sealed zones | supervision / photos |
| After works | reinstate fire stopping and update register | close-out photo + status update |
FAQs
Can we just “seal around the tray” and leave the rest?
Often no. Trays create gaps above/behind runs, and fire stopping may be needed on both faces. If you can’t access a face, record it as an exception and plan how you’ll address it.
Do we need to remove existing foam?
If it’s not part of a tested system (or it’s deteriorated/damaged), it’s usually better to remove and replace with a system-based detail. At minimum, the outcome should be evidence-led and defensible.
What’s the biggest reason defects come back?
Follow-on works. Without clear IDs, documentation, and change-control, later trades add cables and the breach reappears.
What good remedials usually include
- clear defect register and location references
- system-based remediation (not generic “seal it” instructions)
- a close-out pack with photos where practical
Related pages
Note
This article is general information. Align remedials to competent guidance, manufacturer/system requirements, and the building’s fire strategy.