You do not normally need to apply for planning permission to re-roof your house or to insert roof lights or skylights as the permitted development rules allow for roof alterations subject to the following limits and conditions:
Solar panels: View guidance on the planning and building regulations regime for solar panels.
Please note: the permitted development allowances described here apply to houses not flats, maisonettes or other buildings. View guidance on flats and maisonettes here.
Work on a loft or a roof may affect bats. You need to consider protected species when planning work on this type. A survey may be needed, and if bats are using the building, a licence may be needed.
There are two sets of building regulations for roofs:
If you want to carry out repairs on or re-cover less than 25 per cent of the area of a pitch or flat roof, you will not normally need to submit a building regulations application. You will need approval, however, if:
The removal or alteration to any roof elements could affect how the roof works and cause movement to occur. Movement could cause cracks to occur in the walls and, possibly, the eventual collapse of the roof. When performing work on any roof, care should be taken to ensure the roof will continue to perform effectively and without any movement.
Existing Pitched Roofs
The existing roof structure that forms the loft space has a number of timber elements that make the overall pitch. Each element enables the roof to span across the building and support the tiles/covering on top as well as being able to transfer the loads (weight) created by any wind and snow down to the walls.
Listed below are the typical elements of a pitched roof:
Existing Flat Roofs
Flat roofs are more simple and generally consist of joists that span the gap between two walls. These are covered by panels which, in turn, are covered in felting or other such coatings as required.
Further information
After a period of time the roof on existing buildings will need to be replaced. In most situations, this work will need Building Regulations approval.
Flat Roofs
Some repairs to flats roofs will not require an application for approval under the Building Regulations. However, if the roof with integral insulation is to be replaced then you may be required to upgrade this 'thermal element' of the structure and reduce the amount of heat that was originally lost, by upgrading the insulation.
Pitch Roof
If the existing roof covering is to be replaced with a different material to its original for example, slate to tiles, then approval under the Building Regulations is likely to be needed to ensure the roof will be adequate in terms of structural stability (applicable where the replacement tile will be significantly heavier or lighter than the existing), and also meets requirements in respect of fire safety and energy efficiency (see above).
If the new roof covering is significantly heavier or lighter than the existing one, the roof structure may need modifying and/or strengthening, and you are advised to check with a structural engineer or surveyor before commencing with works.
Energy Efficiency
As a roof is defined as a thermal element, the work to re-cover a roof should also include for improving the thermal insulation properties of the roof.
A rooflight is a window that is installed within a pitched roof or flat roof normally to give more light to rooms or spaces within the home. Approval under the Building Regulations will generally be needed for the installation of a new rooflight for the following reasons:
Structure
To install a rooflight in a roof generally entails cutting part of one or more of the roof's rafters or joists away. The cut ends of the rafter/joist will need to have new support introduced - usually achieved by fixing two pieces of timber together which span across the new opening on either side. These double timbers are called 'trimmers'.
The adjacent rafters or joists to which these trimmers are fixed may also need to be strengthened as they will be supporting the load transferred from the cut rafters or joists. This strengthening can be achieved by fixing a new rafter or joist to them which must also run the full length.
Weather Proofing
Once a rooflight is installed the edges (where the rooflight meets the roof) will require weather proofing as well as the glass of the rooflight itself. This is commonly carried out by using lead flashing or with proprietary kits supplied with the rooflight. Manufacturers of rooflights may be able to advise on how this can be carried out.
Ventilation
A room that the rooflight is to serve will need to be ventilated. Ventilation can be achieved by using the rooflight for both rapid and background venting.
Ventilation of the existing roof void(s) will have to be considered as air must still be allowed to flow from one to another.
Energy Conservation
Dwellings are required to be energy efficient. A method of achieving greater energy efficiency is to take steps to reduce the amount of heat that is lost through the glazing in both windows and doors.
If you are to install windows and doors you should be aware that they need to comply with the requirements of the Building Regulations in relation to the amount of heat that can pass through the door or window, including the frame, which is measured as a U-Value. This U-value should not be exceeded. For information on the maximum U-Value allowed please refer to Approved Document L-1B, Table 1.
Making significant changes to thermal elements (walls,roodor floors) would normally require Building Regulations approval and require the thermal insulation of the element to be upgraded to a reasonable standard. Walls are defined by Regulation 2(3) of the Building Regulations 2010 as being thermal elements.
The extent to which the work on the element is controlled and the amount of upgrading needed depends on the particular circumstances of the thermal element. Generally, when it is renovated then it should be upgraded, where it is cost effective to do so, to the standard set out in the Approved Document. See section 5 and Appendix A of Approved Document L1B.[a1]
The definition in Regulation 2(3) is extracted here for convenience from the Building Regulations 2010
(3) In these Regulations "thermal element" means a wall, floor or roof (but does not include windows, doors, roof windows or roof-lights) which separates a thermally conditioned part of the building ("the conditioned space") from:
(a) the external environment (including the ground); or
(b) in the case of floors and walls, another part of the building which is:
(i) unconditioned;
(ii) an extension falling within class7 of Schedule 2; or
(iii) where this paragraph applies, conditioned to a different temperature,
and includes all parts of the element between the surface bounding the conditioned space and the external environment or other part of the building as the case may be.
(4) Paragraph (3)(b)(iii) only applies to a building which is not a dwelling, where the other part of the building is used for a purpose which is not similar or identical to the purpose for which the conditioned space is used.
Further guidance on this is available in Approved Document L1B covering:
You should fully consult the Regulations and the Approved Document and, if you are in any doubt, seek advice before commencing work. The definition of a thermal element does not include windows, doors, roof windows or rooflights.
Pitch Roofs
Insulation can be placed between the ceiling joists. Again, the thickness will vary depending on the material you choose to use.
If the roof has no ceiling then the insulation can be placed between the rafters and ventilation maintained as described above - in which case the ridge should also have vent tiles installed to allow for through ventilation.
Further guidance on insulating roofs can be found in Approved Document L1B, Table A1.
When converting areas to liveable space then it is likely that any existing roof needs to be checked for adequacy in terms of weather resistance and thermal insulation.
If the underside of the roof (the ceiling) is to be lined with plasterboard then the resulting void may also need to be ventilated.
Flat roofs
The roof will need to be ventilated. Typically, a 50mm gap should be maintained between any insulation and the underside of the roof. Through ventilation is then achieved by incorporating eaves venting.
If the roof is to be re-covered then the insulation can be installed on top of the joists making a ‘warm deck’ roof (check with manufacturers for details). This avoids the need for ventilation and the roof covering can be re-applied over the top.
Pitch Roofs
Insulation can be placed between the ceiling joists. Again, the thickness will vary depending on the material you choose to use.
If the roof has no ceiling then the insulation can be placed between the rafters and ventilation maintained as described above - in which case the ridge should also have vent tiles installed to allow for through ventilation.
A new roof will be required to:
There are generally two types of roof construction used:
To enable compliance with the requirements of the Building Regulations to be demonstrated, full details of the new roof will be needed - including materials and their dimensions and performance properties.
Covering
The materials used to cover the roof should be durable and capable of resisting the elements of the weather. With a pitched roof the type of tile or slate you wish to use will be partly governed by how steep or shallow the slope is. If the roof is close to a boundary, which is often the case, the roof should also have properties to limit the risk from fire spreading across the boundary.
Ventilation
Not all roofs need to be ventilated. Ventilation is not required to a warm roof system, which is where the insulation is placed above the joists or rafters. Otherwise ventilation is required and this is known as a 'cold roof system'.
When ventilating a roof the air should be able to enter at one end and travel through to the other end where it can exit.
Further Information
The loads (weights) to be supported are from various sources:
Wind Load
The roof should be tied down to the structure to stop it from lifting in times of strong winds. This is normally achieved by providing straps that are approximately 1.2m long with a cranked end which is fixed to the wall plate (to which the roof timbers are fixed) and then the inner skin of the wall at every 2.0m centres.
Spreading
The timbers that make a pitch roof (rafters), will always want to spread apart. Ceiling joists are a way of stopping this as they are fixed to the bottom end of the rafters and stop them from pulling apart. However, if you wish to take away the ceiling and be able to see roof, then another system should be used to tie down the rafters to the walls and stop them from spreading. For a roof that is to be exposed with no ceiling joists, you may wish to seek advice from an engineer.
There are two ways to insulate a roof:
Warm Deck – this is where the insulation is placed on top of the rafters/joists and the roof covering is then placed over the insulation. No ventilation is required for these types of roofs.
Cold Deck – this is where the insulation is placed between the joists/rafters or in between the ceiling joists in the case of a pitch roof. Ventilation is required for these roofs.
Flat roof
Pitch Roof
This is an introductory guide and is not a definitive source of legal information. Read the full disclaimer here.
This guidance relates to the planning regime for England. Policy in Wales may differ. If in doubt contact your Local Planning Authority.
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