Project Planner: Environmental factors

Michael Holmes explains the importance of understanding flood risk and wildlife protection when undertaking a project.

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Flood risk and wild life protection need to be taken into account when planning a home-improvement project, explains experienced renovator Michael Holmes in the fourth part of the Project Planner series.

IMAGE ABOVE: Photography by Alan Hunt


How will flooding affect my development plans?

If you live in a part of the country at risk of flooding, this will be taken into consideration when determining any planning applications for an extension, influencing the design and even preventing certain types of extension. To help the local planning authority (LPA) determine your application, you will be required to submit a Flood Risk Assessment (FRA). If you live in a part of the country at risk of flooding, this will be taken into consideration when determining any planning applications for an extension, influencing the design and even preventing certain types of extension. To help the local planning authority (LPA) determine your application, you will be required to submit a Flood Risk Assessment (FRA).

How do I assess the level of a flood risk?

Visit the Environment Agency website ( and enter your postcode on the map, identifying your property and the colour coding for the level of flood risk – FZ1 (white) being the lowest, with no impact on your project, and level 3b (dark blue) being the highest. The codes run as follows: FZ1, low risk; FZ2, medium risk; FZ3a, high risk; FZ3b, functional flood plain.

Why do I need to tell the local authority?

The LPA will refuse to register your application if you fail to provide the necessary FRA. If your project is a householder application and the additional footprint does not exceed 250 square metres, or form a separate dwelling (annexe), then you need to complete and submit a standard FRA form produced by the Environment Agency. Larger projects and new dwellings require a full FRA, and this is likely to cost upwards of £450, depending on the scale of the scheme.

Can I mitigate against flood risk?

As long as suitable flood mitigation measures are taken into account in the design, the project will not be refused on grounds of flood risk. This will entail either building the extension at the existing ground floor level and incorporating flood mitigation measures in accordance with Improving the Flood Performance of New Buildings (, or raising the flood level 300mm above the known or modelled 1-in-100-year river flood level or 1-in-200-year sea flood level.

What about permitted development?

If your proposals are classed as permitted development, then the planning policy on flood risk will not apply, but it would make sense to take flood risk into account in the design.

Where an existing office building is converted into a dwelling under last year’s new permitted development rules, allowing changes of use is subject to a prior approval process from the LPA, and flood risk will be taken into account.

What about a basement extension?

Basement extensions and cellar conversions in flood zones are highly vulnerable but may be permissible depending on local planning policy on non-habitable rooms. Self-contained basement flats are not permissible in zones FZ3a or 3b, and only in FZ2 in exceptional cases.


Will trees in my garden affect my proposals?

You can normally remove trees in your garden to make way for development, provided that it does not affect an endangered species’ habitat or disturb nesting birds (an ecologist should advise on the timing and mitigation measures). If the trees are protected, either via a statutory preservation order, as a condition of an existing planning approval, or because you live in a Conservation Area, you will need planning permission to alter or fell them.

How much will a tree survey cost?

A tree survey to support a householder planning application will cost £300-£400 plus VAT. The local authority will not register the application without one if they feel it is required.

What about permitted development?

Even if your home-improvement proposals constitute permitted development and so do not require a planning application, you cannot alter or remove protected trees without obtaining permission.

Will I need to submit a tree survey?

If your project requires the removal of trees, you will need to submit a tree survey together with your planning application, so that the local authority can assess whether any protected trees will be affected, and it then has the chance to issue preservation orders on important trees that are considered to bring significant amenity benefit to the local area. You can find out whether any trees in your garden are protected by searching the local charges register via the local authority. An order can protect a single tree, or all trees within a defined area or woodland, but not hedges, bushes or shrubs.

If a tree preservation order is issued you can appeal the decision, but statutory protection comes into effect straight away. The order does not necessarily prevent permission being granted, but a local authority will consider the impact of your proposals and may suggest you look for alternative design solutions. They are not only looking to prevent important trees from being felled but also to ensure the root area is protected from excavation or construction nearby.

It is a good idea to get a tree surgeon or arboricultural consultant to advise on the best approach. If you deliberately damage or destroy a protected tree, or if you cause or permit such work, you could be liable to an unlimited fine.

Protected Species

Will local wildlife affect my project?

If your proposals potentially affect the habitat of a European protected species – including bats, owls, voles, dormice, badgers and reptiles – you’ll need to submit a biodiversity survey and report with your planning application. If the survey identifies any species present, proposals will be needed to mitigate the project’s impact. Planning authorities will refuse to register an application unless the appropriate surveys are submitted, and as conducting the reports is restricted to very narrow windows at certain times of year, this can result in significant delays. It therefore pays to anticipate what is likely to be required and when this work can be undertaken

Do I need a survey?

Habitat surveys are likely to be necessary if there are any of the following features or habitats on the application site or within one kilometre: a designated site of conservation interest; ancient parkland or woodland; meadows; grassland; parkland; water, rivers or streams.

Also, if the proposals affect: a disused roof void (such as a loft) with unobstructed voids or uneven roof coverings; a traditional timber-framed building (a barn or farm buildings); hanging tiles or wood cladding; large trees with complex form; cellars, ice houses and so on.

How much will a habitat survey cost?

The first step is to commission a Phase One habitat survey, which combines a desktop study and a site walk-through. Costing from £399 plus VAT, it is best done between April and October.

If evidence of a protected species is found, a Phase Two survey will determine population size, use of features and estimated levels of disturbance, but can only be undertaken at certain times depending on species. The most common requirement for householder projects is a bat survey, costing £300-£400 plus VAT, possible from May to October. The survey will also recommend the mitigation measures required, which will usually be made a condition of planning permission.

Once granted, any work affecting bats, great crested newts, otters or dormice will require a European Protected Species licence, which grants an exemption to the law to allow work to proceed in accordance with the approved plans

How much might it cost?

Mitigation measures can prove expensive and can only take place at certain times of year. If bats are present in the loft the planners might require a space to be left for them to roost, or an alternative habitat to be created elsewhere on site, which can cost thousands of pounds. In rare instances where there is no room for an alternative habitat, and limited loft space, the presence of bats could make the project unviable

Will a permitted development project be affected?

Even if your project is permitted development (and so does not require a planning application), it is an offence to disturb or harm endangered species protected by European law.