Which reports a replacement dwelling needs

The reports needed for a replacement dwelling sit somewhere between a householder extension and a new build on a bare plot, and the ordering matters more than the length of the list. Demolition is what makes this project type different. Bats, nesting birds, asbestos, buried oil tanks and the loss of habitat all attach to the building you are taking down rather than the one you are putting up, and several of them are seasonal.

Start the ecology work first. Everything else can be run in parallel.

Policy tests for replacing an existing house

Local plan policies on replacement dwellings almost always control size, usually by reference to the volume or floor area of the existing house, sometimes by reference to its footprint. Read the policy before you draw anything, because a scheme designed to a client's brief and then measured against a percentage cap is a scheme you redraw.

Green Belt sites are stricter again. National policy treats the replacement of a building as an exception to inappropriate development where the new building is in the same use and not materially larger than the one it replaces. Materially larger is a judgement, and authorities interpret it through their own policy and through appeal decisions in their area.

Two questions decide whether the policy applies at all. Is the existing building a lawful dwelling, and is it still a dwelling? A building that has been derelict and unoccupied for years may have lost its residential use through abandonment, in which case the scheme is a new dwelling in the open countryside and a different set of policies applies. Establish this before the design work starts.

Bat and bird surveys before demolition

Bats are protected under the Conservation of Habitats and Species Regulations 2017 and the Wildlife and Countryside Act 1981. Demolishing a building that holds a roost without a licence is an offence, and the protection applies whether or not the council asks for a survey.

A preliminary roost assessment can be done at any time of year. It looks at the building for features and evidence: gaps at the ridge, lifted tiles, soffit voids, droppings, staining. If it finds potential, emergence and re-entry surveys follow, and those run from May to September with the best results between May and August. Miss the season and the scheme waits a year.

Where a roost is confirmed, a Natural England mitigation licence is needed before demolition, and the licence application requires a detailed method statement and compensation, usually bat boxes or a purpose-built roost feature in the new building. Link the first mention of this work in your documents to the relevant report type, and note that a bat survey has to be carried out by a licensed ecologist. This is not a report an AI draft can replace.

Nesting birds are the other demolition constraint. The main nesting season runs from March to August, and it is an offence to damage an active nest. Either demolish outside the season or have an ecologist check immediately before works start.

Biodiversity net gain and the exemptions

This is where replacement dwellings catch people out. The householder exemption from the biodiversity gain condition covers development within the curtilage of a dwellinghouse, such as extensions and outbuildings. A replacement dwelling is a new dwelling, so it does not automatically get that exemption.

Two other exemptions may apply. The de minimis exemption covers development that impacts less than 25 m2 of on-site habitat and less than 5 m of on-site linear habitat such as hedgerow. A rebuild confined to an existing footprint and hardstanding can fall within it. A rebuild that reshapes the garden, removes a hedge along the drive or takes in a paddock will not.

The self-build and custom build exemption is the other route, and it has its own conditions on the number of dwellings and the size of the site. Check the current exemption regulations rather than assuming, because the detail has been amended since the regime started.

Where no exemption applies, you need a habitat baseline survey, a metric calculation and a Biodiversity Net Gain Assessment supporting a gain plan that the authority approves before development starts. The Environment Act 2021 regime expects the metric to be completed by a competent person.

Tree protection during demolition

Demolition traffic is harder on trees than construction traffic, because it happens before anyone has installed protective fencing and because the plant is heavier.

Check for Tree Preservation Orders and for conservation area status, which brings a six week notice requirement for works to trees. Then check root protection areas against the demolition access route and the position of the skip. Under BS 5837:2012 the root protection area has a radius of twelve times the stem diameter measured at 1.5 m above ground, and a 600 mm oak therefore claims a radius of 7.2 m that no tracked machine should cross.

The practical output is a tree protection plan and an arboricultural method statement, conditioned and enforced. Where access is tightly constrained, ground protection using a cellular confinement system is the usual answer, and it needs specifying before the contractor arrives with scaffold boards.

Contamination from tanks and outbuildings

Older houses in rural areas frequently have a heating oil tank, and a leaking tank is one of the commonest contamination findings on a single plot. Domestic garages and outbuildings add asbestos cement sheeting, and former agricultural use adds fuel stores, sheep dip and buried waste.

The starting document is a Phase 1 desk study, prepared in accordance with BS 10175 by a suitably qualified person, covering historical mapping, a site walkover and a preliminary conceptual site model. If it identifies potential sources and pathways, a Phase 2 intrusive investigation follows. Both are covered by the contaminated land assessment report type, and both are work for a suitably qualified and experienced person rather than a draft alone.

Asbestos has its own regime. A refurbishment and demolition survey under health and safety law is required before demolition, separately from anything the planning system asks for.

Drainage, flood risk and finished floor levels

If the site sits in Flood Zone 2 or 3, or is one hectare or more, expect a flood risk assessment. And do not assume the householder exemptions help: a replacement dwelling is not householder development, so the sequential test may be applied. Check the position with the local planning authority early, because a sequential test on a single plot is an awkward exercise.

Finished floor levels are the detail that decides these applications. Raising levels above the existing house is normal in flood risk terms and often unwelcome in design terms, particularly where the new dwelling has to relate to neighbours. Resolve it before validation, not at committee.

Foul drainage matters too where the existing house runs to a septic tank. A replacement dwelling with more bedrooms may exceed what the existing system can take, and the general binding rules for small sewage discharges apply.

Demolition notification and the documents it needs

Demolition of a dwellinghouse outside a conservation area is normally permitted development under Part 11, subject to a prior approval application covering the method of demolition and the restoration of the site. The application needs a method statement, a site plan and evidence of consultation where required.

Inside a conservation area the position is different and more serious. Demolition of a building in a conservation area is relevant demolition requiring planning permission, and carrying it out without consent is a criminal offence. Where the replacement dwelling sits near a listed building, the setting test applies as well, and our guide to the reports needed for development next to a listed building sets out what that adds.

One practical point on the levy. Where the existing building has been in lawful use for a continuous period of at least six months within the three years before permission, its floorspace can usually be deducted from the levy calculation. An empty house that fails that test produces a levy bill on the whole of the new floorspace, which is a large number to discover late.

Browse the 66 report types to see which of these a replacement dwelling on your site is likely to need.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.