Façades & external wallsAssemblies and finishes
Façade and external wall evidence, checked against the project detail.
External wall build-ups attract scrutiny. Building Control, fire engineers and clients ask pointed questions about cladding, carrier boards and system evidence.
The Bench reviews the evidence behind the external wall or façade build-up and sets out, in writing, what the documents support for the detail actually proposed.
ScopeEvidence review. Not certification, Building Control or design sign-off.
The questions that arrive with a façade query
Building Control has questioned the external wall
A submission or sign-off is waiting on evidence for the wall build-up, the cladding or the board behind it.
The fire strategy makes comments about the façade
The strategy assumes a level of performance that the documents now have to support for the actual construction.
Is the carrier board covered?
The finish has evidence behind it, but the carrier board it sits on may not be part of the tested system.
System evidence versus project detail
System evidence exists, but the project detail differs in substrate, cavity, fixings or layers — and someone wants that difference explained.
The paperwork behind an external wall question
Every enquiry is different, and you do not need a complete set before getting in touch — send what you have. These are the documents that usually matter:
- System test, classification or assessment evidence for the wall build-up
- Product data sheets and declarations of performance for boards and components
- Certificates or assessments for the cladding, render or facing system
- Drawings and details of the proposed external wall
- Fire strategy comments or Building Control correspondence raising the question
- Installation guidance for the system as it is intended to be built
Where façade evidence falls short
The evidence is for a different build-up
The wall that was tested or assessed is not the wall on the drawing — a layer, cavity or substrate has changed.
The carrier board is the weak link
Evidence for the finish is assumed to cover the board behind it, when the board was never part of the tested system.
Component evidence presented as system evidence
Separate product documents are combined as if the complete assembly had been tested together — product-level documents do not establish assembly performance.
The question belongs to the fire strategy
The documents can inform the discussion, but the judgement sits with the appointed fire engineer — and the evidence needs to be organised so they can make it.
Where external wall problems concentrate
A conceptual figure from the published review. It shows where the failure record concentrates; it is not a design detail for any project.
Fig. 1Cavity vs No Cavity? · External Issue 02 · August 2026 · conceptual figure
A written façade evidence position you can use
The Bench reviews the external wall evidence against the detail actually proposed, and puts the position in writing.
- Review the system evidence against the drawn external wall detail
- Map which parts of the build-up are covered by which document — and which parts are not
- Identify carrier board, component and substitution gaps in the evidence for the build-up
- Set out the evidence position in writing for Building Control or fire engineer discussions
- List the next evidence steps where the documents do not yet answer the question
The output is written — a review note, clarification note, gap register or evidence summary you can use with the project team. We quote before any written work starts.
Clear about the limits of the review
The Bench reviews evidence and gives written guidance. For façades and external walls in particular, the limits matter:
Not part of the review
- Fire engineering judgement or façade fire strategy approval
- Certification, testing or product approval
- Building Control or other statutory sign-off
- Design responsibility for the external wall or its details
Those decisions stay with the competent person or organisation appointed on the project. Our written review supports them; it does not replace them.
External wall evidence under scrutiny?
Send the question, the wall detail and the documents you already have. No charge to submit an enquiry — we quote before any written work starts.
Not sure where your question sits? Find your route ›
What helps us start
- The question, as it was put to you
- What the product or build-up is, and where it is going
- The documents you already have — data sheets, reports, certificates, drawings
- Any comment from Building Control, the designer or the client
- When you need an answer
You do not need a complete set to get in touch — send what you have.