Householder Extensions and Conversions – Page 3

Secondary glazing in a listed house

Secondary glazing is reversible, which is why it is the alteration most conservation officers accept in a listed house. The detail that decides consent is where the new frame is fixed and how its members line up with the original sash.

Converting a cellar to habitable space in a terrace

Converting an existing cellar is often not development at all. Lowering the floor, forming a light well or creating a bedroom below ground changes that, and flood risk is where these schemes usually fail.

Cat slide roofs on a single storey rear extension

A continuous slope over a rear extension looks right on a steep roof. It also drops the eaves, which engages the 3 metre boundary limit and costs usable headroom.

Keeping the chimney stack on a terrace roof extension

On a terrace the stacks are the skyline, so officers assess the proposal against the row. Retaining one changes the dormer position, the flashing and the restraint.

Floor levels and thresholds where a garden slopes away

On a falling garden the floor level decides the threshold, the retaining structure and the drainage. Permitted development height is measured from the higher ground at the house.

Extending above an attached garage: what the council asks

Class A allows side extensions only as single storey, so a first floor over a garage always needs an application. The foundations usually decide the design.

Rear extensions over a drain run and the build over

A build over agreement is nothing to do with planning permission, and permitted development does not cover it. How to find the sewer and design around it.

Garden rooms with a shower room: incidental or not

Class E covers buildings incidental to a house, not additional living accommodation. Where washing facilities tip the balance, and how foul drainage is dealt with.

Garden offices and the incidental use test explained

Working from home is incidental. Running a business with staff, clients and deliveries is not. Where the line sits under Class E, and how to get certainty.

Porch design limits and the three square metre rule

Class D of Part 1 of the GPDO allows a porch within three dimensional limits that apply together. The 2 metre distance from a highway boundary is the one that rules out most terraces.

Front light wells to a terrace basement: the rules

A light well dug in the front garden of a terrace falls outside permitted development. Here is what the highway authority, the case officer and the drainage engineer each want to see.

Air source heat pump siting, noise and the boundary rule

The noise calculation, not the boundary distance, is what decides most heat pump installations. Here is how the test works and where it goes wrong.

Householder Extensions and Conversions9 min read

Rendering a brick house: design policy and limits

Render over brick is permitted development in most places and refused in a conservation area. The harder question is whether the wall can take it at all.

Garage conversions: habitable standards and parking loss

Most garage conversions are permitted development until you find the condition on the original permission requiring the garage to be kept for parking.

Corner plot side extensions and the second frontage

On a corner plot the side elevation is a frontage, and that single fact removes most of the permitted development you expected to have. Here is what applies instead.

16 October 2026Read article →

Side return infill: keeping light in the middle room

Infilling the side return gives you the kitchen you want and takes light from the room behind it. Here is how the geometry works and what an officer will expect to see.

16 October 2026Read article →

Rooflights or a rear dormer on a hipped roof loft

On a hipped roof the choice is between rooflights, a rear dormer and a hip to gable. How each affects head height, the volume allowance and your options in a conservation area.

Householder Extensions and Conversions6 min read

A rooflight against a roof lantern on a flat roof

A lantern adds height, and height is what the permitted development limits measure. On an existing roof the 150mm protrusion limit usually settles it.

15 October 2026Read article →

Thresholds and level access on a sloping plot

A level threshold on a sloping plot is an argument between access, drainage and damp. The resolution is a 1:5 section, a channel with a real outlet and levels set at both ends.

Reinstating sash windows as part of an extension scheme

Restoring lost sash windows while you extend gives a conservation area officer something to weigh against the new volume. Here is what needs consent, what the details must get right, and which drawings to submit.

Parapets, upstands and shared gutters on a terrace extension

A flat roofed terrace extension fails at the party wall first. Settle the upstand height, the party wall consent and the overflow position before the drawings go in.

Rendering the extension and leaving the house in brick

A rendered extension on a brick house falls outside the permitted development materials condition. Here is the design argument that gets one approved, and the detailing behind it.

Juliet balcony detailing on a rear elevation

A flush balustrade with inward opening doors behaves like a large window. Anything you can stand on is a balcony, and the permitted development position changes.

Replacing a conservatory with a solid roof extension

A solid roof ends the conservatory exemption. The two places these projects fail are the existing base, never designed for the load, and the eaves height near a boundary.