Loft Conversions Regulations

loft-conversionAs a general rule, planning permission is not required unless you are planning to make extensions or alterations of the roof space and your project does not correspond to the specific rules and regulations, issues by the authorities.

The home owner is not obliged to ask for permission in case the loft conversion project meets the following limits and conditions:

  • The owner of a terraced house is allowed to build additional roof space without asking for permission if the extension is high no more than 40 cubic metres. (Please, bear in mind that there might have been some extensions made by the previous owner and these should also be included in the total height allowed. )
  • The detached and semi – detached houses’ owners are not required to wait for the project approval in case the additional roof space is no more than 50 cubic metres in height.( The same specification, mentioned above, is valid for the detached and semi – detached houses)
  • Extension that goes beyond the current roof slope, facing the highway will not be allowed
  • The extension must not be higher than the highest point of the roof
  • The owner is required to complete the project by using building materials that resemble those, used for the building of the existing house
  • Any attempts for building a balcony, a veranda or a raised platform will not be tolerated
  • The side – facing windows have to be obscure glazed. They should be installed in a way that allows opening 1.7 metres above the floor
  • A building permission will not be issues for designated areas. (The national parks and the Boards, the conservations areas, the World Heritage Sites, the Areas of Outstanding Natural Beauty are all among the designated areas.)
  • The owner has the responsibility of ensuring at least 20 cm space between the roof extension and the original eaves.
  • The roof extension must not swing over the upfront wall, part of the original house

Please, remember that the rules and regulations discussed above are valid for houses and therefore if you own a flat, a maisonette or any other building you should take a look at the other guidance.

Regulation of other building projects

House Extensions
Fence Installation
Conservatory Construction
Kitchens and Bathroom Refurbishment
Boiler installation and Central Heating

Protected Species

In case your loft or the space under the roof is home for bats, the building procedure may have a negative influence on them. That’s why you might need to make a survey and do your best to protect the bats. Sometimes, an additional license is needed.

Building Regulations

If you want to turn a loft or an attic into an additional, functional room, then, you will, by all means, need an approval for starting a building project.
Please note that the section bellow describes the regulations for a loft conversion procedure at a house that has no more than two stores. Although the specifications for extending a three storey house or a maisonette are quite the same, the project might lead to extension to other parts of the building.
These regulations are necessary due to the fact that the loft conversion project has to live up to the following requirements:

  • the stairs should be safe for climbing
  • the sound insulation should be appropriate
  • there should be a secure method for escape in an event of fire
  • the structure of the house should be remain stable regardless of the new extension
  • the new floor has to be stable as well

Every house owner would do their best in order to make the loft space more functional but if you want to install a flight of stairs or line the walls, you have to be prepared for more extensive work and respectively The Building Regulations rules to apply
You are advised to get in touch with the Building Control authorities, discuss your project and get a useful piece of advice. You also have to double check if your loft conversion project falls within The Party Wall etc. Act 1996.

Boarding-out for storage

All too often, the timber joists that serve as a floor of the loft and a ceiling of the rooms downstairs are not sustainable to supporting heavy “loads”. In other words the chances to get an unstable floor construction despite your efforts is really high. That’s why the joists have to be tied to the pitch members of the roof in order to avoid their spreading.

If you stuff the loft with various items, you are likely to cause yourself a trouble with the joists that work beyond their capacity. There is an option of placing flooring boards over the joists but you are required to turn to the Building Regulations Application to Building Control.

Creating a liveable space

If you are planning to turn your loft into a spare bedroom or any other “livable space”, much more efforts have to be made towards the aim of completing the project. Bearing all the significant alterations in mind, you should be well aware that these can cause damages to the property if they haven’t been carefully planned and performed.

Further Information

These are some of the main elements, intended to meet the requirements of the Regulations:

  • New internal elements
  • New Dormer
  • Stairs
  • Safety in an event of fire
  • Existing walls and foundations

The sections, mentioned bellow are the major elements for meeting the requirements of the regulations:

  • Drainage
  • Roof
  • Internal walls
  • Electrical installation
  • Doors and windows
  • Kitchen
  • Bathrooms

Existing walls & foundations

Load bearing walls

As far as the stability of the existing walls is concerned, every house owner has to think of the best way for supporting the new joists. In case the joists are going to be supported by an existing wall, it has to be continued to the foundation or at least another type of adequate support to be ensured.

Existing openings

There are some houses where the following problem exists: the load-bearing wall has been either removed or it was designed to serve as a lounge and a beam, made of steel or timber and placed over the opening. A thorough checking procedure has to be made to make sure that the beam would be capable of carrying the new load, once the loft conversion project is finished.

Existing foundations

Contrary to a popular notion, the weight the new loft will add, will transfer extra load to the foundations. However, that’s not completely true. The weight of the additional load will be at a reasonable range.
Some exceptions apply though. If the foundations are unable to bear the additional load, they should be checked and underpinned. Feel free to ask your Building Control Body or an engineer for some help.

New Dormer

In general, most dormers are made of timber and they consist of a roof, side walls (also knows as cheeks), front wall. There are two alternatives for supporting the side walls:
the first one includes doubling and bolting the side walls together, then constructed off the rafters
if the cheeks are at the edges of the roof, they can be taken down and supported by the doubled floor joists. Another option is using the beam or the external walls as a supporter

Dormer Walls

The external wall can either support the front one or be set back from the external line of the house. Support by the new floor joists is possible, especially when they have been redesigned to bear some additional load of this wall.
These is one more thing to be taken into consideration when constructing a dormer. It has to be designed in a way that prevents fire spreading to or from the neighbouring property.

Removal of rafters

Installing a window, rooflight or dormer usually includes making an opening in the existing rafters.
The new dormer can support the remaining sections. If you have installed a new window or rooflight, installing timbers across the head of sill will be necessary

Using a double trimmer that can transfer the load to the existing rafters is recommended. However, strengthening the rafters on the both sides is also recommended because that will make them stable and capable of carrying more load.

New internal elements

These are the elements, which make the loft conversion procedure possible:

  • Floor and beams
  • Walls
  • Doors

Floor & beams

The chances to have ceiling joists that can adequately support the load from the new construction, are really slim.
Solving this problem timely can save you a lot of troubles in future. All you are supposed to do is to install new floor joists between the existing ones. If the existing walls are stable, the new joists can be supported on them. Steel or timber beams can be used provided that they are fire resistant.


The new walls play an important role in supporting the existing walls and the new roofs, especially if the roof supports have been removed. This kind of support is usually presented by low level walls, which contribute to reducing the span of the rafters. The loadbearing walls usually separate the new rooms from the old ones but what they have in common is that they have to be fire – resistant.

Sound Insulation

Sound insulation is a must and if you own a detached or a semi – detached house, you might be asked to improve the insulation between the loft, you have just converted and the neighbours loft. If they decide it is really necessary, you might be asked to test the insulation but the testing can not take place unless your neighbours agree to let the testers into their property. If needed, the party wall will undergone some further alterations so the insulation between the properties is excellent.

Fire safety

When planning a loft conversion project, you have to plan ahead and predict the route for escape in case of fire. In other words fire protection measures are needed in the existing parts of the house.

For instance, if you have a two storey house and you have just had your loft converted, you will have to ensure the presence of fire resisting doors and, in some cases, partitions for the stairway. The reason is that it is too risky to escape from the loft in case of fire.
You are advised to install smoke alarms and check and improve the condition of the existing fire alarm system.


Every home owner should ensure the adequate protection against fire and if you are too short of space and therefore the installation of a typical flight of stairs is impossible, you should opt for the so called “space saving” stair. Retractable ladders or stairs won’t be accepted by the authorities. Your stairs should meet some specific criteria in order to be approved.

Opening for new stairs

The celling joists between the existing rooms and the loft space should be cut but you should ensure replacement support. In most cases, timber trimmers around the opening or a double trimmer would do an excellent job transferring the excessive weight to the remaining timbers.

More information here and here.


This guide should not be regarded as a source of legal information. It is predominantly designed to explain the rules and regulations for loft conversion projects that take place in England. The Wales’ policy might be different. Please, contact your Local Planning Authority for further assistance.