It changes which rules apply, yes. GOV.UK’s permitted development guidance states that “buildings which are attached to the house are not permitted under Class E (they would be subject to the rules in Class A)”, so an attached design is judged under the extension rules rather than the outbuilding rules that carry the 2.5m/3m/4m pergola heights.
That matters before a design is fixed, not after. The extension rules measure a structure against the house itself, taking depth from the rear wall, width against the original house and height against its existing eaves. They also bar a verandah outright, so an open frame bolted to the wall can land on either side of that line. It shares load paths and drainage with the roofline above it too. My pergola planning permission page is the place to start, and BCP Council will confirm the position for your own wall.
Do I need permission if I add a clear or solid roof later?
Only if the finished structure breaks the limits. A freestanding pergola has to stay inside the same height rules once a roof is on: 2.5 metres if any part sits within 2 metres of a boundary, otherwise 3 metres overall, or 4 metres where the roof is genuinely dual-pitched, with eaves no higher than 2.5 metres. A roof that pushes it past those figures needs an application, and one that does not, does not. Whether a roofed structure also picks up a building regulations requirement is a separate question I could not stand up from a published source, so ask BCP Council before you add one.
Can I build a pergola in a Bournemouth or Poole conservation area?
Usually yes, but not automatically. BCP Council’s 48 conservation areas, among them Meyrick Park and Talbot Woods, Branksome Park and Chine Gardens, West Cliff and Poole Hill, and Christchurch Central, narrow what counts as permitted development rather than removing it outright, and Planning Portal states that on designated land “buildings, enclosures, containers and pools at the side of properties will require planning permission”. A council can also remove permitted development rights altogether with an Article 4 direction, which Planning Portal notes is most common in conservation areas, so check your own address before assuming the standard limits.
If you want a straight answer for your own garden, ring Alfie on 07841 319560.
Related: back to planning permission for decking and pergolas: the questions Bournemouth homeowners ask.
Related: can a pergola be 2.5 metres high without planning permission?