A bungalow replaced with a two storey house

A replacement dwelling application is judged against a different policy from an extension, and the arithmetic is usually where it turns. The walkthrough below is illustrative: a 1960s detached bungalow on a wide plot in a village, demolished and replaced with a two storey four bedroom house. Every figure and response described is illustrative rather than drawn from a real decision.

The scheme took eleven months from first survey to decision, and about four of those months were avoidable.

The existing bungalow and the policy on replacement dwellings

The bungalow sat centrally on a plot of roughly 0.12 hectares, inside the settlement boundary of an adopted local plan, with detached neighbours either side, both two storey. Brick and concrete tile, a shallow pitched roof, a detached garage and a mature beech on the rear boundary.

The adopted plan carried a policy on replacement dwellings that allowed them within settlements subject to three tests: that the replacement is of a scale appropriate to the plot and the surrounding pattern of development, that it does not harm the amenity of neighbouring occupiers, and that any increase in volume is proportionate.

Inside a settlement boundary, those tests are design tests rather than the volume ceiling a countryside or Green Belt policy would apply. That difference is the single most useful thing to establish at the outset, because a policy written for the open countryside would have made this scheme undeliverable.

Demolition mattered too. Demolition of a dwellinghouse is treated as development, so it was covered by the replacement application rather than dealt with separately. Had the plot been in a conservation area, the demolition would have needed permission in its own right.

Testing the volume and footprint increase against the local plan

The proposal roughly doubled the internal floor area. Volume increased less than that, because the bungalow had a large footprint and the new house was taller and narrower.

The submission set out both numbers. Existing volume measured externally to the eaves and ridge, proposed volume on the same basis, footprint before and after, and the proportion of the plot covered. It also gave the same figures for the two neighbouring properties, which is the comparison an officer will make anyway.

That last table did most of the work. The proposed house had a smaller footprint than the house to the north and a comparable ridge height to the house to the south, and once that was on one page the scale argument largely resolved itself.

Where the applicant nearly went wrong: the original intention was to retain the detached garage and count it out of the calculation. Ancillary buildings within the curtilage are frequently counted in a volume comparison, and the policy did not say either way. The garage was included in both the existing and proposed figures, which was the conservative reading and removed an argument.

Street scene, ridge heights and the neighbours either side

The bungalow was the odd one out in a street of two storey houses, which helped. A Design and Access Statement with a street elevation drawn across five properties, at a consistent scale and with ground levels surveyed rather than assumed, showed the proposed ridge sitting below one neighbour and level with the other.

Three design moves came out of the neighbour analysis:

• The first floor was set in from the northern boundary by 1.5 metres more than the ground floor, to keep the 45 degree line from the neighbour's nearest habitable window.
• Two first floor windows on the flank elevation were obscure-glazed and fixed shut below 1.7 metres.
• The ridge ran parallel to the street rather than perpendicular, which reduced the apparent bulk from the neighbouring garden to the rear.

Levels are worth a separate warning. The plot fell about 700mm from front to back, and an early drawing had taken finished floor level from the existing slab without checking. The topographical survey moved the ridge by nearly half a metre.

Ecology: the bat check before demolition

A bungalow with a shallow pitch, felt under concrete tiles and open soffits is a plausible bat roost, and demolishing a roost without a licence is a criminal offence under the habitats regime.

The preliminary roost assessment was carried out in March and found droppings in the roof void plus features on the north elevation. That triggered emergence surveys, which can only be done in the active season, and the ecologist scheduled two visits in May and June.

One common pipistrelle roost was confirmed. The outcome was a mitigation licence application to Natural England, integrated bat boxes in the new build, a timing restriction on the roof strip, and supervision by the licensed ecologist on the day.

This is the part of the programme that cannot be compressed. Had the Preliminary Ecological Appraisal been commissioned in September rather than March, the emergence surveys would have waited until the following May and the application with them. Survey seasons decide self-build programmes more often than planning officers do. The specific requirements for roost work are set out on our bat survey page.

Biodiversity net gain applied. A replacement dwelling is not householder development, and the garden habitat affected exceeded the de minimis threshold, so a baseline was measured and the landscape scheme was designed to deliver the required gain on site through native hedgerow and a small wildflower area, recorded in the Biodiversity Net Gain Assessment.

Drainage, levels and the existing connection

The bungalow drained to a public foul sewer in the road with a private connection of unknown condition. A CCTV survey found a partially collapsed section under the front garden, which had to be replaced regardless of the planning outcome.

Surface water was the more interesting question. The existing roof and drive discharged to the same combined connection, which the water undertaker would not accept for the enlarged roof area. The scheme moved surface water to a soakaway in the rear garden, with an infiltration test showing acceptable rates in the sandy subsoil, and a permeable drive.

Root protection for the beech constrained where the soakaway could go. The arboriculturist and the drainage engineer resolved it between them in about an hour, which is an hour well spent compared with discovering the conflict on site.

The objections received and how the design responded

Four objections during the publicity period.

Loss of light to the north neighbour's kitchen window, answered by the 45 degree analysis and the first floor set-in.

Overlooking from the rear first floor windows, answered by window positions and a distance of 23 metres to the rear boundary of the properties behind.

Out of character with the street, which the street elevation drawing addressed and which the officer's report did not accept as a reason for refusal given the two storey context.

Construction disturbance, answered by an offered condition on hours and a construction management note.

One objection was withdrawn after the applicant met the neighbour and showed them the drawings. That is worth doing before submission rather than after.

The permission and the conditions attached

Permission was granted under delegated powers with fourteen conditions, of which four were pre-commencement and had been agreed in writing in advance.

The ones that mattered: materials samples before superstructure, the bat mitigation strategy implemented in full with the roof strip supervised, the landscape and biodiversity scheme with a 30 year management plan, surface water drainage details as tested, and obscure glazing to the flank windows in perpetuity.

A note on cost. Community Infrastructure Levy liability was reduced by the demolished floorspace, which qualified because the bungalow had been in lawful residential use for the required period before permission. Self-build relief was also claimed. Both required forms submitted in the right order and before works started, and missing that sequence is an expensive mistake that cannot be undone afterwards.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. Bat survey and licensing work must be carried out by a suitably licensed ecologist.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. Browse the report types to see what a replacement dwelling pack usually contains.