Trafford’s 1-Metre Rule: How Close Can a Side Extension Be to the Boundary?

Planning a side extension in Timperley, Sale, Altrincham or elsewhere in Trafford? You may have heard that you need to leave a 1-metre gap to your boundary, or that this can reduce to 750mm at ground-floor level.

These dimensions can influence your design from the outset. However, they need to be understood in context—particularly when deciding whether your project needs a planning application or qualifies as permitted development.

What is the 1-metre rule?

Trafford’s house-extension guidance seeks a 1-metre side gap for first-floor and two-storey side extensions. For single-storey side extensions, it seeks a 750mm gap.

The council explains that these gaps help retain spaciousness between houses and, at ground level, provide a route to the rear so bins need not be stored prominently at the front. These principles are set out in its SPD4 approval report, section 4.5.

Does this mean 750mm downstairs and 1 metre upstairs?

That is a useful starting point when exploring a stepped side-extension design: the ground-floor part sits closer to the boundary, while the first floor is set further in.

However, 750mm is not an automatic allowance for every ground-floor proposal. The council’s stated distinction is between single-storey extensions and first-floor/two-storey extensions. A combined design needs assessment as a whole.

Corner plots also require particular care: Trafford’s guidance identifies a minimum 2-metre boundary gap for single-storey proposals in that context, potentially more where needed to preserve spaciousness. Trafford SPD4 approval report, sections 4.5–4.6

Is this the same as permitted development?

No. Local planning guidance and national permitted development rules serve different purposes.

A qualifying single-storey side extension may be permitted development without a householder planning application. National rules do not impose a general 1-metre or 750mm side-boundary setback.

Instead, they include limits on width, height and location. For example, the side enlargement must be single-storey, no more than half the original house’s width and no higher than 4 metres. Where it is within 2 metres of a boundary, its eaves must not exceed 3 metres. Other conditions and restrictions also apply. Government householder technical guidance

The first step is therefore to establish the correct planning route. A boundary gap that is relevant to a planning application should not be presented as an extra national permitted development requirement.

For more on this distinction, read our homeowner’s guide to permitted development.

Think beyond the measurement

When developing your design, consider how the remaining passage will actually work. Downpipes, gate posts and other projections can make a narrow route less usable.

Accurate drawings should show the boundary, the proposed walls and roof, and the space that remains. It is also worth considering how you will move bins, garden equipment and bikes between the front and rear.

An extension should give you useful new rooms while keeping the rest of your home practical.

Planning a side extension in Trafford?

Reid Design Limited is based in Timperley and helps homeowners across Trafford and Greater Manchester explore their options for extending their homes.

Explore our house extension plans and design services to see how we can help you develop a layout that responds to your property, your priorities and the relevant planning requirements.

If you’re thinking about a side extension, I’d love to hear your ideas. Get in touch for a free initial feasibility consultation, and we can explore what’s possible.

General guidance for homeowners. The appropriate boundary separation and planning route depend on the property and complete proposal.