McGaw v The Welsh Ministers [2021] EWCA Civ 976
McGaw is an important Court of Appeal decision on how the height of a proposed outbuilding is measured under the Welsh General Permitted Development Order where the building is constructed flush against an ordinary boundary wall.
The court held that, on these facts, the neighbour’s garden immediately beyond the boundary wall could be treated as the ground immediately adjacent to the proposed building.
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- Neutral citation
- [2021] EWCA Civ 976
- Court
- Court of Appeal (Civil Division)
- Judgment date
- 30th June 2021
- Judge
- Lord Justice Lewison, Lady Justice Asplin and Sir Timothy Lloyd
- Case number
- C1/2020/1799
The proposed garden room sat against a boundary wall
Mr McGaw owned a house in Sketty, Swansea. He proposed a single-storey garden room in the south-west corner of the residential curtilage.
The garden sloped upwards away from the house. Earlier excavation works had altered the levels near the boundary and an existing brick boundary wall separated Mr McGaw’s land from the neighbouring garden.
The proposed garden room would abut that wall. The dispute was how to identify the surface of the ground immediately adjacent to the building for the Welsh Class E height restrictions.
The relevant ground does not have to be in the developer’s ownership
The Welsh Ministers argued that the measuring ground had to be within the dwellinghouse curtilage. The Court of Appeal rejected that proposition.
The purpose of the height restrictions is to limit the visual impact of permitted development. There was no good planning reason why ground just across the ownership or curtilage boundary should automatically be ignored if it was in fact the ground nearest to the proposed building.
A boundary wall is not ground
Immediately next to the proposed garden room would be the existing boundary wall. But the wall itself could not be treated as the surface of the ground.
The Welsh Ministers suggested that a tiny or notional gap between the two walls could supply a measuring point. The court rejected that approach. A wafer-thin notional gap was not something which could fairly be described as ground with a surface.
The neighbour’s garden could be immediately adjacent
Beyond the ordinary boundary wall was the neighbour’s unbuilt garden. The court held that, on the particular facts, this was capable of being the ground immediately adjacent to the new building.
That interpretation was pragmatic and consistent with the purpose of the GPDO. Requiring the garden room to be set back by an artificial 150mm simply to create a strip of measuring ground would have produced a wasteful and rather absurd result.
The result may differ where the intervening structure is larger
The court did not establish a rule that land beyond every boundary structure will always be immediately adjacent.
Sir Timothy Lloyd gave the example of a much larger intervening structure, potentially even another house. In a more unusual situation it might no longer be realistic to describe the ground beyond that structure as immediately adjacent. That would be a question of fact and degree.
The Court of Appeal did not decide the backfilling issue
This is an important limitation on the case.
The High Court had held that the relevant ground level for a proposed building should be assessed by reference to the position which would exist if the proposed development were completed, including proposed backfilling. The Welsh Ministers sought to appeal that conclusion, but permission to appeal on that ground was refused.
The Court of Appeal therefore did not decide that separate point. Its judgment was confined to whether the neighbour’s garden beyond the boundary wall could qualify as the immediately adjacent ground.
McGaw is a Welsh GPDO case
The decision concerned the 1995 GPDO as it applies in Wales. The wording and operation of the English GPDO should not simply be assumed to be identical.
For Welsh permitted development, always check the current Welsh Order and the specific class relied upon. Planning Geek keeps the Welsh provisions separate from the English GPDO for this reason.
Read the full McGaw judgment
The approved Court of Appeal judgment is held in the Planning Geek case law library. Gold Members can open the protected PDF below.
Related Planning Geek guidance
See GPDO Article 1 in Wales for the interpretation provisions which apply across the Welsh Order.
McGaw Case Law Page Updated: 9th September 2026