Preflex vs. Open Wiring: Which Cable Method for Your Project?
Comparison of Preflex conduit systems and open cable installation in Belgium. Advantages, disadvantages, and AREI/RGIE fire safety classes at a glance.
Preflex vs. Open Wiring: Which Method Suits Your Project?
Short answer: Preflex is a pre-assembled conduit with cables already pulled through — ideal for new builds, where it is cast directly into concrete. Open wiring (e.g., XVB surface-mounted or in cable trunking) is better suited for renovations, where conduits are difficult to retrofit.
What Is Preflex?
Preflex is a flexible corrugated tube (conduit) with the appropriate cables already pulled through at the factory. In Belgium, this method is extremely popular for new construction: the conduits are laid during the shell construction phase on the concrete slab or in the screed, then cast in. This way, cables are fully protected and can be replaced later if needed.
Comparison: Preflex Safe vs. Standard Preflex vs. Open Wiring
| Criterion | Preflex Safe | Standard Preflex | Open Wiring (XVB) |
|---|---|---|---|
| Sheath | Halogen-free (LSOH) | Standard PVC | No conduit, cable direct |
| CPR fire class | Cca-s1,d1,a1 (cable in conduit) | Eca (cable in conduit; the CPR class refers to the cable, not the conduit itself) | XVB with CPR marking Cca-s1,d2,a1 (required for new installations in certain installation methods; older stock may still be classified as Eca) |
| Application | New build, public buildings | New build residential | Renovation, surface mount |
| Cable replacement | Yes | Yes | No (permanently installed) |
| Cost | Highest | Medium | Lowest |
| AREI compliance | All applications | Residential allowed | All applications (if cable type correct) |
Advantages of Preflex
- Clean installation: No visible cables, everything is concealed or cast in.
- Future-proof: Cables can be replaced or added later without breaking open walls.
- Protection: The conduit protects against mechanical damage.
Disadvantages of Preflex
- More expensive than direct cable installation (materials + labour).
- Only practical for new builds/major renovations — difficult to retrofit in simple renovations.
- Bending radii must be respected: tight curves make future cable pulling difficult.
What Does the AREI/RGIE Say?
The AREI does not prescribe a specific installation method — both are permitted. What matters is the fire reaction class (CPR regulation): individually installed cables require at least Eca (Art. 5.2.7.2). In bundles, hollow walls, and building cavities, at least Cca is required (Art. 5.2.7.3, Art. 4.3.3.5b). Note: timber-framed walls (common in renovations) count as building cavities!
The conduit may be filled to a maximum of 40% with cables (general installation rule per trade standards), so that future cable pulling remains possible.
When to Use Which Method?
- New build → Preflex (Safe for highest fire protection)
- Renovation → XVB cable in trunking or surface-mounted
- Partial renovation → Combination possible (new circuits in Preflex, existing ones kept)
Related Articles
- What Changes with the AREI 2026?
- Bathroom Electrics: Zones and Cable Types
- Old Buildings and AREI Part 8
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