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Requirements for a Loft Conversion


Building Regulation Approval


Approval of building regulations are needed if you convert your loft into a LIVEABLE space. There are a few regulations to consider for a loft conversion on a 2 storey house. Conversions in maisonettes or houses over 3 storey will be similar but may be more extensive and you may need to extend other areas of the building.


The regulations will ensure:

1. Structural strength of the new floor in order to make sure it is sufficient

2. The stability of the structure (including the original roof) is not jeopardised

3. There is a safe fire exit

4. The stairs leading to the conversion are safe

5. The sound insulation is reasonable between the conversion and other rooms


Building regulations are likely to apply if you are planning on making the conversion more accessible of more liveable i.e. installing a stair to it, boarding it out and lining the walls and rafters. It is worth contacting Building Control to discuss your plans and seek any advice you also need to find out if the work you carry out falls within The Party Wall Act 1996.


Boarding for Storage

Typically, existing timber joists which form the “floor” of the loft are not sufficient to support a significant amount of weight. If you choose to lay floor boards over the existing joists in the loft space, it may require a building regulation application to Building Control.


Planning Permission

Planning permission is not usually required. However, it will be required if you plan to extend or change the roof space and it exceeds specific limits and conditions. These conditions can be found in Schedule 2, Part 1, Class B of the Town and Country Planning Order 2015. There are different rulings for “any other alteration to the roof of a dwelling house” which can be found in Schedule 2, Part 1, Class C.


A conversion in your loft is permitted and does not required planning permission providing you follow the limits and conditions listed below:


1. You do not exceed 40 cubic metres of additional roof space for terraced houses, or 50 cubic metres for detached or semi detached houses

2. You do not exceed beyond the plane of the existing roof slope of the principal elevation that fronts the highway

3. Your conversion is not higher than the highest part of the roof

4. You use similar materials to the existing house

5. You do not have balconies, raised platforms or verandas

6. Any side facing windows must have an opening 1.7 metres above the floor and be an obscure-glaze

7. You are not permitted for roof extensions in designated areas

8. Apart from hip and gable ones, roof extensions must be set back as far as practical and be at least 20 centimetres from the original eaves

9. You cannot have a roof enlargement that overhangs the outer face of the wall of the original house


• Please note: Previous roof space additions must be included within the volume allowances, it may be the previous owner created additional space which needs to be considered.

• Designated areas consist of World Heritage Sites, National Parks and the Broads, Areas of Outstanding Beauty and Conservation Areas

• Permitted development allowances are applicable to houses and not to:


1. Areas where a planning condition, Article 4 Direction or other restriction that limits permitted development rights

2. Converted houses or houses created through permitted development rights to change uses

3. Maisonettes and flats

4. Other buildings



Typically, a dormer is constructed from timber. A dormer consists of the roof, side walls (cheeks) and front wall which faces the garden. The cheeks can have support by:

• Rafters being doubled and bolted together with the cheeks and hen constructed off the rafters

• If the width of the dormer lead to the cheeks being at the edge of the roof, then the cheeks can be taken down to the floor and supported off the floor joists (which are doubled) or on a beam, or in some cases by the part or external walls


Dormer Walls

The front wall can be supported off the external wall, or if it is intended to be set back from the external line of the house. It can be supported off the new floor joists. This should be designed to cater for the extra lead of this wall.

The dormer may need to be built to give resistance to a fire spreading to or from a neighbouring property. The extent of this construction will be subject to the size of the dormer cheek and its closeness to the boundary.


Removal of Rafters

For a roof light, window or dormer to be installed, it is usually necessary to cut and opening in the existing rafters. The remaining sections of the cut rafters can be supported by the new dormer. If it is a new window or rooflight support can come from installing new timbers (known as trimmers) across the head (top) or sill of the new opening.


Depending on the size of the created opening, you may need to have 2 timbers fixed together (double trimmer) to transfer the load to the existing rafter on either side of the new opening.

I hope this provides a bit of guidance and can allow you to appreciate the depth of work involved in creating a dormer. If this is something you want to have a quote for then please be sure to click here for a no obligation quote.

Carpenter in Kent


Hours of work:


Monday – Friday       8am-4pm


Email: john@jbbespokecarpentry.co.uk


Telephone: 01622 92 44 69

Mobile: 07470272837


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JB Bespoke Carpentry Logo, Carpenter in Kent
Carpenter in Kent

Carpenter in Kent

JB Bespoke Carpentry Logo, Carpenter in Kent
Carpenter in Kent