External wall materials and the combustibles restriction

Regulation 7(2) of the Building Regulations 2010 requires every material forming part of an external wall, or of a specified attachment, on a relevant building to achieve European classification A2-s1,d0 or better. That is a Building Regulations rule, not a planning rule, and it bites after your planning permission is granted. Which is why a material palette agreed at planning stage on an 18 metre residential block can turn out to be undeliverable, forcing a section 96A amendment or worse.

Architects working on tall residential schemes should treat the restriction as a design constraint from the first sketch, and should say so in the Design and Access Statement.

Which buildings the restriction applies to

A relevant building is one with a storey at least 18 metres above ground level, measured as the regulations describe, which contains one or more dwellings, an institution, or a room for residential purposes. The 2022 amendments to the regulations brought hotels, hostels and boarding houses within scope, closing a gap that had allowed combustible cladding on buildings with sleeping accommodation outside the residential definitions.

The 18 metre figure recurs elsewhere and it is worth keeping the regimes separate in your head. A higher-risk building under the Building Safety Act 2022 is at least 18 metres or seven storeys with two or more residential units, which governs the gateway process and the Building Safety Regulator's role. Sprinkler provision in new blocks of flats is driven by an 11 metre threshold in Approved Document B, which is lower again.

Below 18 metres, regulation 7(2) does not apply, and external wall construction is judged against the guidance in Approved Document B on fire spread over external walls. Many clients and warranty providers now specify non-combustible construction below the threshold anyway, so check the insurance position before you assume timber cladding is available.

Components caught and components exempt

The restriction applies to materials that form part of the external wall, which includes the cladding, insulation, sheathing boards, cavity barriers where they form part of the wall, render and its backing, and any brackets and rails.

Regulation 7(3) sets out the components excluded from the requirement. The list covers items where the fire risk is judged to be low or where compliance is impractical: door and window frames, glass, electrical installations, seals, gaskets, fixings, sealants, membranes, thermal break materials and a small number of others. The exclusions are specific and closed, so a product outside the list has to meet the classification even where it is present in tiny quantities.

Two consequences follow for specification. A single non-compliant component can compromise the whole wall, and the classification has to be evidenced for each product rather than assumed from a system approval. The test and classification route for a whole system under BS 8414 with the BR 135 criteria is not available for relevant buildings, because regulation 7(2) prohibits the materials regardless of system performance.

Balconies, spandrels and solar shading

Specified attachments are where the restriction reaches beyond the wall itself. They include balconies attached to an external wall, devices for reducing heat gain within a building such as solar shading, and solar panels.

Balconies are the recurring design problem. A timber decking surface, a composite decking board, a timber handrail or a polycarbonate privacy screen on a balcony attached to a relevant building will not achieve the classification. The available answers are metal or mineral decking, glass or metal balustrades, and perforated metal screens, all of which read differently from the timber balcony in the planning drawings.

Spandrel panels between windows form part of the external wall and need the same classification. Solar shading fins, brise soleil and projecting reveals in a coloured aluminium composite all need checking, because the composite core is the issue rather than the finish.

Where a scheme's environmental strategy relies on external shading to meet Part O overheating criteria, resolve the shading material before the planning drawings are fixed. Otherwise the overheating strategy and the material palette contradict each other.

Reconciling the restriction with design policy

Design policy asks for materials that respond to local character. Regulation 7 rules out a group of materials that often deliver that response. The tension is real and the way through it is to be explicit rather than to hope.

Set out in the Design and Access Statement that the building is a relevant building, that the palette has been selected to satisfy regulation 7, and that the material samples condition should be drafted to allow substitution with an equivalent that meets the classification. A condition worded as brick type X and timber cladding type Y, with no substitution mechanism, is a trap you will pay for later.

The Design and Access Statement is also where you explain why the elevation does not use the material the local design guide favours. Officers accept the answer when it is given up front and resent it when it appears in a discharge application two years later.

Heritage settings and material palettes

In a conservation area or next to a listed building the problem sharpens, because the officer is asking for materials that match a historic palette and the regulation is removing several of them.

What works: facing brick and brick slips on a non-combustible backing, terracotta faience and rainscreen terracotta, natural stone and stone rainscreen, mineral render systems on masonry or on non-combustible board, pre-patinated copper and zinc, and glass reinforced concrete. What does not: timber boarding, timber shingles, uPVC, most composite panels and most organic bound render carriers.

Colour and texture do most of the work in a heritage setting, and those are available in the compliant materials. A dark bronze anodised aluminium window reveal reads closer to a historic frame than a white uPVC one ever did.

Specifying materials at planning stage

Work in this order and the later gateways get easier.

1. Confirm at concept stage whether the building is a relevant building, and record the measurement that establishes it.
2. Build the palette from materials with an A2-s1,d0 or A1 classification, including every attachment.
3. Check each product's classification report against EN 13501-1, rather than relying on a manufacturer's summary sheet.
4. Ask for the material samples condition to be worded to permit equivalent substitution on classification grounds.
5. Where the planning drawings show a balcony, show the compliant handrail and deck detail rather than a generic line.
6. Keep the external wall build-up consistent across the Design and Access Statement, the elevations and the fire statement.

Where the application is for a relevant building, an Article 9A fire statement is likely to be required and the material strategy has to be consistent with it. On who can sign that document, see who is competent to author a fire statement. Core planning decisions interact too, since firefighting shaft requirements shape the plan at the same time as the wall shapes the elevation.

Evidence to keep for the later gateways

Gateway Two under the Building Safety Act 2022 requires a full plans submission to the Building Safety Regulator before construction starts, and the information you assembled at planning stage feeds it.

Keep the classification report for every external wall product and attachment, the drawing revision that fixed the build-up, the correspondence with the manufacturer confirming the product reference, and the record of any substitution and why it was accepted. This is the beginning of the golden thread, and reconstructing it later costs far more than maintaining it.

An illustrative example: a 21 metre block of flats in a conservation area, designed with a brick base and stained timber upper cladding. The building is a relevant building, so the timber cannot be used. The revised palette uses a lighter facing brick with a recessed mortar joint for the upper floors and bronze anodised aluminium reveals, balconies switch from composite decking to an aluminium plank with a perforated metal screen, and the overheating strategy moves from external timber louvres to fixed metal fins. The elevation reads as intended and the specification is deliverable.

PlanScope drafts a Fire Statement alongside the other supporting documents, structured to UK planning policy and flagging the facts it cannot verify. A fire statement for a relevant building must be prepared by someone with the necessary fire engineering competence under the Building Safety Act 2022 framework and Article 9A of the Development Management Procedure Order 2015, so the draft is a starting point for that professional rather than a substitute.

This is general guidance, not legal advice; check the position with your local planning authority, your building control body or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.