Are there building regulations covering loft conversions?

Planning permission is not normally necessary for loft conversions, although this does depend on a number of conditions (for example, there must be no extension higher than the highest part of the roof, no balconies, and there are volume limits too, as well as a number of other factors to consider).

However, building regulations are always part of the process for loft conversions, whether the conversion needs planning permission or not.

Can my property be converted?

Do you usually only pop your head up into the loft to bung in a few surplus boxes that will probably never see the light of day again? If so, it’s time to get up there with your torch and tape measure to find out what you’re working with.

The main concern will be the head height of your existing property. Ideally, you need a minimum of 2.2m head height in your existing loft space. This should be measured from the APEX of the roof to the top of the existing joist. Remember, you will lose some of this height when your new floor and ceilings are installed.

It is still possible to carry out a loft conversion if your head height is below 2.2m; we’ve done so with finished ceiling heights as low as 1.85m.

Ultimately, we’ll be able to advise you and hopefully find a solution so that you can experience the benefits of a loft conversion.

Do I need planning permission for my loft conversion?

You don’t normally need to obtain planning permission for your loft conversion, provided that:

  • The house is a single family dwelling and not a flat or maisonette
  • The proposed extension or dormer window will not be raised above the highest part of the roof
  • The slope of any part of the roof, which faces a highway, will not be extended (excluding hip-to-gable conversions)
  • The loft conversion does not amount to more than 40 cubic meters in the case of a terraced house, or 50 cubic meters in any other case. This is measured externally.
  • When combined with any other existing extension to a house, it does not exceed the permitted development allowance

You will need to apply for planning permission if:

  • Your property is a flat
  • The existing ridge line to your roof needs to be raised
  • The slope or any part of the roof that faces a highway is to be altered (excluding hip-to-gable conversions)
  • The proposed loft conversion exceeds 40 cubic meters in the case of a terraced house or 50 cubic meters in any other case. This is measured externally
  • The proposed loft conversion, combined with any other existing extension to a house, exceeds the permitted development allowance
  • The building is listed as being of special architectural or historic interest
  • The building is situated in a conservation area
  • The permitted development rights of your property are restricted by conditions attached to a previous planning permission or your property deeds
  • An “Article 4 Direction” covers the building

AWC Loft Conversions will prepare plans and building calculations, and make sure the necessary notices and permissions are agreed with your local authority.

How long will my loft conversion take?

Depending on the size and complexity of your conversion, building work is normally completed within six to eight weeks.

We’ll confirm the expected time scale of your conversion before we start any work on your property.

Will there be much disturbance while my loft conversion is carried out?

In all honesty, there will be some disturbance – to carry out and complete the work quickly and efficiently, we’ll need builders to be at your property on a daily basis. However, the first two-thirds of the project will be carried out from the scaffold through the roof, without disturbing the house internally.

We’ll only need to actually be inside when we break through to install the stairs and carry out any necessary alterations to the landing area.

Regardless of where we’re working, our team will be professional, courteous and thorough in cleaning on a daily basis before leaving the site.

Will a loft conversion add value to my property?

Yes, it has been proven that by converting your loft area into additional living space the price of your property will increase.

How do loft conversion building regulations work?

Each and every loft conversion must be inspected for approval, either by your local authority’s Building Control team or by independent, regulated inspectors.

No matter who is charged with inspecting your conversion, a building notice is required from your local authority before any construction work can begin. We will apply for the building notice on your behalf. Once the application is submitted, construction cannot begin until at least seven days later.

Three inspections will be required during the construction of your loft conversion. After the final inspection has taken place and the work has been passed (i.e. your loft conversion meets the building regulations), a completion certificate will be issued. It’s important to keep this somewhere safe so you can prove the safety of your conversion if you ever sell your property.

What do loft conversion building regulations cover?

UK building regulations will cover a number of elements of a loft conversion, including the floor, the structural soundness and the insulation. The regulations are there to ensure that the new structure is completely safe.

This includes:


Using your loft as a living space will mean that the floor has to hold a lot more weight than it did originally. The floor of your new loft conversion must be strong enough to hold this added weight, or it won’t meet building regulations.

Any joists and load-bearing walls must support the extra weight, and you may also have to install steel beams to hold up the new joists.

Fire doors, fire alarms and fire escapes

There are two options for fireproofing your loft conversion:

  • Change the doors on all habitable rooms on every floor leading to the staircase to fire doors, and install a mains-wired or linked fire-alarm system on each floor
  • Install a mains-wired or linked fire-alarm system to all habitable rooms and landings

Either way, you’ll still need doors enclosing the stairwell to the front door, and all glazing in these areas must be fire-rated.

Open-plan living room

If you have a open-plan living room, you’ll need a Plumis sprinkler system installed, along with either of the above options.

Stairs and access

The stairs to the new floor of the loft conversion must be safely designed. Any staircase to the new living space must be wide enough to allow anyone to use them easily in case of an emergency.

Headroom and ceiling height

Your loft conversion must offer sufficient headroom and a high enough ceiling for it to be used as a practical living space. This applies both to the living area itself and to the staircase up to the conversion.

Insulation depth, energy efficiency and U-Value

Any dwelling should be energy-efficient. Any walls, roof slopes, ceilings and new windows and doors installed in a loft conversion will be measured to determine how much heat passes through the glass and framework. The amount of heat lost must not exceed a certain limit, known as the “U-Value”. Even if the rest of your property doesn’t comply with this standard, your new loft conversion must have sufficient insulation to meet the building regulations.

In terms of keeping sound transference to a minimum, insulation between the conversion and the rooms below must be sufficiently effective, as must the insulation in any new internal walls. If you live in a terraced or semi-detached house, you may also find that you have to improve the insulation between yours and your neighbours’ lofts.


Your new loft conversion must be ventilated properly to make sure it meets building regulations. There should be a window that is a twentieth of the total floor area of the new living space, and there should be a mechanical fan of sufficient power if you are installing a bathroom. The roof void must also be ventilated to prevent condensation.

Will I need a party-wall agreement?

Yes, you’ll need a party-wall agreement if you are in a terraced or semi-detached house. For more information, take a look at the Party Wall Act information booklet here.

Can my loft be converted under permitted development?

Since changes were made to planning law in October 2008, it’s very likely that your loft can be converted under permitted development. Planning will only be required under certain circumstances, listed above.

Permitted development is the best way to maximise your potential space, as planning permission will usually mean some constraints on the size of your conversion.

In cases where work can be done under permitted development, a certificate of lawful development may be obtained prior to commencing the project.

What is a certificate of lawful development?

These certificates prove that your proposed extension or conversion is within your permitted volume. They can be obtained from local authorities and are not planning applications.

Plans will need to be submitted to your local authority, who will check and confirm in writing the legitimacy of the proposed work. The certificate can take up to six weeks to arrive, though having one is not a legal requirement.

Do I now know everything I need to about loft conversions?

The information we’ve provided is simply to be used as general guidance when you start considering a loft conversion. It’s worth noting that each case will be judged individually.

If you have any questions about loft conversions and building regulations in your area, you should call your local authority, or get in touch with us for further advice.

You can also find more information here:



AWC Loft Conversions is a trading name of LV-426 Ltd Registered Office Address: Office 63, 1o5 London Street, Reading, Berkshire, RG1 4QD


01189 678 428


[email protected]

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