Putting a rooflight or skylight beside Birkdale's tall villas among the sandhills

The railway to Southport is what turned Birkdale from farmland and sandhills into a suburb, and the street plan still follows it. Large villas went up first, in brick with slate roofs, steep gables and generous attics, set back from the road on plots with room for gardens. Closer to the station and the village centre the plots shrink, and bay-fronted terraces fill the streets, many with a flat-roofed rear extension added in some later decade.

Further from the line, building came in waves. Inter-war semis and detached houses appear on the roads leading out, followed by post-war housing, bungalows and newer detached homes on the edge of the golf courses and the dunes. A good number of the biggest villas have since been divided into flats, which matters for planning and for how a roof can be changed.

The villa roof is a landscape of its own. Multiple gables meet in valleys, chimney stacks stand in the middle of the slope, and dormers break the main planes. Opening a new window means finding a clear stretch between all of that, and the survey usually begins by walking the whole roof rather than a single slope. The terrace roof, by contrast, is a plain pitch with a ridge, shallow and narrow, where a single roof window on the back pitch can make the landing or a loft room usable. Many of these terraces were built with a lean-to scullery at the back, later raised or flattened, so the rear roof often has two or three different coverings meeting each other, and the survey records where each one starts.

The newer houses are simpler again. Their roofs are mostly tile over trussed rafters, and the work there tends to be a sun tunnel to an inner landing, a roof window on a bungalow loft or a lantern on an extension. Dune-side bungalows and chalet houses sit low enough to reach without much fuss. Where a bedroom has been built into the slope, a roof window may double as its way out, so long as it meets the Approved Document B dimensions.

Attics are where Birkdale villas give the most away. Servants' rooms and box rooms under the slope have often been turned into bedrooms or studies, usually with one dormer or a small window in a gable. A pair of roof windows on the slope beside the dormer can double the daylight without touching its cheeks, and an old rooflight over the stair is a candidate for replacement rather than for a second opening beside it.

Planning decisions for Birkdale rest with Sefton Council, which also holds the conservation area maps, and the first thing we check on any Birkdale survey is whether your road sits inside one. Where it does, the council cares how a new unit looks from the street, and a slim conservation rooflight on a rear slope usually makes the case easier. What officers expect on a protected street is covered in this note on slim conservation rooflights, and the map at sefton.gov.uk shows whether your address falls inside the boundary.

A single house with no special control is the simple case: the permitted development rules sit in the planning explainer for skylights, and we measure your roof against them on site. The front slope of a villa is highly visible, so the page on windows facing the road is worth reading before you choose where a window goes.

Birkdale has a lot of flats. The rights a single house enjoys do not pass to an apartment in a divided villa, which means a rooflight there goes to the council as an application, and a listed building adds listed building consent. Ask the freeholder or managing agent before you plan anything, because the roof is often not the leaseholder's to alter.

Sefton Council's building control side is ours to deal with, and the rules behind a notified rooflight job are set out in one place. On a villa the inspector may also want to see the timber around a large opening.

Large openings in villa roofs often cut through old purlins or trimmed rafters, and the council or approver may ask for the beam calculation before they sign it off. We gather that at the survey. The structural detail goes in the written quote with the unit, so that nothing about the timber comes as a surprise once the tiles are off.