Ground-mounted solar and permitted development

What Class B permits

The installation, alteration or replacement of stand-alone solar for microgeneration within the curtilage of a dwellinghouse or a block of flats.

“Stand-alone solar” is defined in the order as “solar PV or solar thermal equipment which is not installed on a building” — so this covers ground-mounted frames, pole mounts and free-standing arrays, but not panels on a shed roof, which fall under Class A instead.

That distinction is worth holding onto, because a shed roof is often the better route: Class A has no area limit and no boundary setback.

Every limit, in one place

Development is not permitted by Class B if any of these is exceeded:

Plus the conditions: site it to minimise the effect on the amenity of the area so far as practicable, and remove it when no longer needed.

What 9 square metres actually buys you

This is the number that decides whether Class B is any use to you, and it is rarely translated into anything meaningful.

Nine square metres is about four to five modern domestic panels. At roughly 210 to 240 watts per square metre, that is 1.9 to 2.2 kWp.

On our own modelling, at 35° facing south:

Against a typical medium household’s 2,500 kWh a year, a Class B array covers a meaningful share — but you cannot scale it up without an application.

The five-metre rule is the real obstacle

The array must not be installed within 5 metres of the boundary of the curtilage.

Not the rear boundary. Not the boundary with a highway. Every boundary.

Work through a typical suburban rear garden: 9 metres wide, 12 metres deep. Take 5 metres off each side and the compliant strip is negative — there is no lawful position anywhere in it, regardless of array size.

You need a plot at least 10 metres wide and 10 metres deep, clear of the house, to have any compliant position at all — and then only a point at the exact centre. To fit a 3 m × 3 m array you need roughly 13 metres in both directions.

That is a large garden, and it is why Class B is, in practice, a rule for rural and semi-rural properties rather than for most housing.

When to apply for planning permission instead

Given the above, an application is the normal route rather than the exception. Some things worth knowing before you make one.

Ground-mounted domestic solar is not a difficult application in principle. It is low, reversible, and supported by national policy on renewable energy. The objections that arise are usually about visual impact from neighbouring property or from a public vantage point.

Screening is the strongest argument you have. Existing hedges, walls, level changes and outbuildings all help. Proposed planting helps less, because it takes years to establish.

Position for views, not just for sun. A slightly worse orientation that is invisible from the lane will usually beat an optimal one that dominates a neighbour’s outlook. Our orientation figures show that south-east or south-west costs only about 6% against due south, which is a cheap price for removing an objection.

Glare is raised more often than it is substantiated. Modern modules are designed to absorb rather than reflect light. Expect the question and be ready to answer it.

Agricultural land has its own considerations if any part of the plot is agricultural rather than residential curtilage.

Roof, shed, or ground?

If you are choosing, the order of preference is usually clear:

The house roof — Class A, no area limit, best structural support, shortest cable runs. Almost always first choice.

An outbuilding roof — also Class A, provided the house is not listed. No area limit and no boundary setback, which makes a large shed or garage roof far more generous than the ground beside it.

The ground — Class B, tightly limited, or a planning application. Genuinely right where the roofs are shaded, unsuitable, or facing the wrong way, and where the plot is big enough to make it work.

There is one real advantage to ground mounting that the limits do not take away: you choose the orientation and the pitch. On a site where every roof plane is poor, an array you can point due south at the optimum angle may beat a larger badly-oriented roof array — and our orientation matrix will tell you by how much.