Plug-in solar and cladding

If your outside wall is clad, or rendered over insulation, you cannot drill into it for a solar panel. This is the most common reason a flat fails the check.

Why a fixing into cladding is a problem

Cladding is a skin. It is fixed to the building through a cavity, on rails or brackets, and it is not built to carry anything hung off it. A fixing that stops in the cladding has nothing structural behind it. In wind, a panel puts a repeated pull on that fixing until it works loose.

There is a second problem. Cladding systems are designed as a sealed and fire-tested assembly. Drilling through it makes a hole through the weatherproof layer and through any cavity barrier or fire break it passes. Water gets in and cannot get out, and the fire performance of the assembly can no longer be relied on. That is why building owners treat any penetration as a serious matter, not a small favour to grant.

The same applies to render over external wall insulation. It looks like a solid wall and behaves nothing like one. A fixing goes through render into soft insulation board and holds only until it is loaded.

How to find out what your wall is

Tap it. A clad or insulated wall sounds hollow and feels warm and slightly soft. Brick and concrete sound and feel dead.
Look at a window reveal. If the wall is much thicker than the structure behind the window frame, something has been added to the outside.
Look at the edges and corners for trims, joints on a regular grid, or panel lines. Cladding has joints. Brickwork has bricks.
Ask your managing agent for the wall build-up. In a block since the fire-safety reviews there is usually a survey on file.
If you still do not know, treat it as clad and do not drill.

If your building has had fire-safety work

Buildings that have had cladding removed, replaced, or are waiting for remediation are usually under strict rules about what can be attached to them. Expect a refusal while work is planned or under way, and expect it to apply to balconies as well as walls. That is not the agent being difficult. Consent given now can invalidate a warranty or a remediation agreement later.

Ask in writing, and ask specifically: may anything be fixed to the balcony structure or the external wall of my flat, and if not now, when will that be reviewed. A written no is still useful, because it settles the question.

The specification sets out where installation is not permitted. There is no building height threshold in the list. The test is what the wall or balcony is made of, and whether the building is under remediation.

Aluminium composite material (ACM) or metal composite material (MCM) cladding systems.
High pressure laminate (HPL) cladding systems.
Timber cladding systems.
Timber balconies.
Buildings subject to external wall remediation works, building safety remediation works, or equivalent restrictions relating to external wall fire safety.

The same list has to appear as a prominent safety warning in the installation instructions, together with an instruction to consult the building owner, freeholder, managing agent or other responsible person if you are unsure what the building is made of.

Separately, you are responsible for keeping escape and rescue routes clear, for not increasing the risk of fire spreading along external walls or balconies to neighbouring properties, and for not fixing anything to a wall that forms a property boundary between dwellings.

Source: Plug-in Solar Device Interim Product Specification v2.0, clauses 5.8 and 8.3.2, DESNZ.

What you can do instead

A clad wall does not always end it. Options that avoid drilling the wall:

Hang the panel on the balcony rail with the clamps supplied, if the rail is structural and can take the load.
Stand the panel on a weighted or ballasted frame on the balcony floor, if the kit offers one and the floor loading allows it.
Use a spot away from the clad wall entirely, such as a garden fence post or a shed, if you have one and the cable still reaches a socket.

All three still need consent in a block of flats, and all three depend on the kit having a mounting option rated for that use. Do not improvise a frame.

Not sure what your wall is?

The check asks about cladding and fire-safety work, and tells you where that leaves you.