4 things to think about before applying to replace an existing dwelling

Planning policies generally support the replacement of existing dwellings. Picture: Getty Images/iSt

Planning policies generally support the replacement of existing dwellings. Picture: Getty Images/iStockphoto - Credit: Getty Images/iStockphoto

In recent years a popular way of building your own home has been through the replacement of an existing house – but applying to do this can be complex. Andrew Boothby, planning consultant at Aitchison Raffety, explains what’s involved.

Andrew Boothby, Aitchison Raffety

Andrew Boothby, Aitchison Raffety - Credit: Archant

Building plots can be very hard to find, particularly in areas like St Albans where much of the land is designated Green Belt. Finding a plot with an existing dwelling and replacing it is an alternative option - and can be a very lucrative one if it is possible to replace a single dwelling with multiple units.

Planning policies generally support the replacement of existing dwellings, but there are pitfalls you need to be aware of before undertaking such a venture.

The site already has permission for residential use

The main benefit of this approach in planning permission terms is that the residential use of the site is already established. On sites where the land and buildings are allocated for other uses, for example commercial, you will need to demonstrate that the loss of employment use is acceptable, as well as designing a dwelling which fits in with the local area, and does not harm the amenity of neighbours.

On existing residential sites this is not necessary. Even in the Green Belt, if the existing site is occupied by a residential dwelling, the principle of replacing it is usually guaranteed, albeit the size of the replacement dwelling could be limited.

Be mindful of policy and site constraints

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While the principle of replacing an existing dwelling with another may be acceptable, the exact extent of what can be achieved differs from site to site. It is important to consider any policy constraints on the land, for example a Green Belt designation, or environmental issues such as flood zones or trees.

In the Green Belt the size of the replacement dwelling you can construct is very tightly controlled. Local policies in the St Albans Council area state a replacement dwelling within the Green Belt can only be the same size as the original dwelling, plus a maximum 40 per cent increase in floor space or 180 cubic metres in volume. In cases where the existing building is a bungalow, the height of the replacement dwelling is likely to be restricted to single storey only.

In Flood Zones 2 and 3 you will need to demonstrate that the replacement dwelling will not increase flood risk. In Conservation Areas, the replacement dwelling must enhance or preserve the character and appearance of the area in order to be acceptable. If there are significant trees on the site you will need to ensure that these are either safeguarded, or, if appropriate, felled and replaced with new planting elsewhere on the site.

Consider the details

Principle aside, you will need to demonstrate that the replacement dwelling is acceptable with regard to its design, scale, siting and access. For instance, on a street comprised of bungalows, the construction of a large two storey dwelling could be considered out-of-keeping with the local environment. Similarly, if the replacement dwelling has more bedrooms, you will need to make sure there is enough outdoor amenity space, sufficient access and parking.

You will also need to carefully consider the amenity of neighbours. A larger, re-sited dwelling could have an adverse impact on the receipt of light, or be overbearing on a neighbour's property and garden.

St Albans City & District Council have a very useful supplementary planning document, Design Advice Leaflet No. 1 - The Design and Layout of New Housing. This document sets out in detail the policies and guidelines steering new housing development within the District.

Using permitted development to add floor space to a replacement dwelling

In areas like the Green Belt, where policies guiding the replacement of existing dwellings are restrictive in terms of increased floor space, it is sometimes possible to gain additional floor space by using the existing property's permitted development rights, provided it has not had them removed.

Currently it is possible to extend an existing dwelling quite considerably without the need for planning permission. The amount and how you can extend under permitted development is guided by a number of criteria, and is dependent on factors such as the location of the site, the layout of the existing building, and whether it has been extended before.

Where extensions are possible under permitted development, these can sometimes be traded to 'negotiate' a higher increase in floor space for the replacement dwelling than that deemed acceptable by Green Belt policy. The key to success is demonstrating that the replacement dwelling would be smaller and less harmful to the Green Belt than if the existing building were extended under permitted development.

Before embarking upon a project involving a replacement dwelling, Aitchison Raffety would be keen to provide initial informal advice. Contact Andrew Boothby on 01442 291798 or via email at andrew.boothby@argroup.co.uk