Planning Permission Loft Conversions & What You Need To Know

Here at Foster & Co Lofts we are all about making your life easier, we know that making any improvements to your home is a big decision and that it can also be disruptive to your home life. Therefore we have decided to put together a special guide for you here on planning permission, when you will need it and when you won’t at your home in London and Hertfordshire.


Planning permission is not required in all cases when it comes to a loft conversion, but it does if the work exceeds certain limits and under special conditions. Some of these are specific to the actual roof itself. Schedule 2, Part 1, Class B of the The Town and Country Planning (General Permitted Development) (England) Order 2015 states; “the enlargement of a dwellinghouse consisting of an addition or alteration to its roof.” This means specifically;

Any alteration to project no more than 150 millimetres from the existing roof plane.

No alteration to be higher than the highest part of the roof.

Side facing windows to be obscure-glazed; any opening to be 1.7m above the floor.

Solar Panels

Solar panels are permitted but also has limits dependent on where you live and if it is a protected area, so this is worth checking out locally. Certain allowances are also apply in general to houses rather than flats, some converted houses, and areas with a planning condition.

Loft Conversions Space

In terms of an actual loft space conversion the limits that you have with regards to not having to apply for planning permission come under the following limits;

A volume allowance of 40 cubic metres additional roof space for terraced houses*

A volume allowance of 50 cubic metres additional roof space for detached and semi-detached houses*

No extension beyond the plane of the existing roof slope of the principal elevation that fronts the highway

No extension to be higher than the highest part of the roof

Materials to be similar in appearance to the existing house

No verandas, balconies or raised platforms

Side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor

Roof extensions not to be permitted development in designated areas**

Roof extensions, apart from hip to gable ones, to be set back, as far as practicable, at least buy phentermine 20cm from the original eaves

The roof enlargement cannot overhang the outer face of the wall of the original house.


We all love animals and it is important to remember that even if we don’t plan on having them to stay, they can sometimes use our homes along with us. You therefore need to consider protected species when doing your loft conversion, specifically bats. If you suspect that bats may be nesting in your roof area then you may need a survey, and a licence might need to be sought.


The load bearing walls in your home will need to be considered for their structural stability as they will need to support the weight of your new living space. For example, if new floor joists are provided and they are to be supported by an existing wall, the wall will need to continue all the way down through the house to a foundation or alternatively the wall will need to be provided with an adequate intermediate support.

The foundations of your home are also a consideration, though in general terms for a loft conversion not a huge amount of weight will be transferred to the foundations of your home. This is of course something that we can help you with in making your decision as we will know the extra weight created.

Some homes that may have had pre-existing walled areas opened up (knocked down) that carried through load bearing into the foundations. Therefore if these were replaced by a beam we may need to check that this will also carry the extra weight of your loft conversion.

We Can Help

This all seems tremendously complicated but we at Foster & Co loft conversions are on hand to support you and provide advise every step of the way. With our wide experience of creating stunning loft conversions we have also come up against many of the sticking points and questions involved with regards to what you can and cannot have, and also with regards to Planning Permission. Feel free to contact us with any queries you have and we will be only to happy to facilitate you in creating your dream loft conversion.

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