Building Regulations and balconies

Balconies can be a great addition to your home: they add extra light and ventilation to a room, provide some outside space and are a great way to take in the scenery. The right balcony can be a real selling point and make your home more attractive to prospective purchasers.

They need to be carefully designed to avoid any negatives: they can be a security risk, making access to upper levels easier for anyone intent on breaking in, especially if the balcony is within easy reach of a wall or fence that can be climbed on, and they can cause neighbour disputes if there are concerns over privacy.

If you are thinking about adding a balcony, you should always seek good planning advice from a design professional like an architect. The creation of a balcony is generally not classed as permitted development under planning law – unless it’s a platform not more the 300mm high (effectively a decked area) or is a ‘Juliet’ balcony that has no platform. Always obtain planning permission, or written confirmation that you don’t need it before you start work. 

If you start work before having obtained planning permission or deviate from the details approved for planning purposes you could find yourself having to remove the balcony, face a fine, or even both. Further guidance on permitted development rights and balconies can be found in the government publication: ‘Permitted development rights for householders: technical guidance’

This article focusses on the Building Regulations and other considerations you need to consider when creating a balcony, to ensure it’s safe to use. 

We’re only addressing balconies in houses here: Balconies in apartments are also subject to other matters like:

Types of balconies

juliet balcony

Juliet balconies 

Named after a scene in the Shakespeare play Romeo and Juliet, these tend to be a large inward opening window or set of doors, or sliding patio doors, with a barrier that is fixed immediately to the outside wall, or between the window or door reveals to prevent people falling out. Sometimes if the windows or doors open outwards the barrier or railing is fixed inside the room (this can make operating the window/door difficult and it may continually slam shut during windy weather).


cantilever, hung and bolt-on balcony

Cantilever, hung, and bolt-on balconies

As the name describes, the balcony protrudes out from the building  appearing to hang in the air and to be a continuation of the floor of the building, where the joists or frame extend out beyond the building line. 




stacked balcony

Stacked balconies

These are supported both by connections to the building and also from posts or pillars that are fixed below them, providing support from the ground or another structure.




rooflight balcony

Rooflight balconies, sometimes called a Cabrio balcony.

These have become popular in loft conversion projects. The rooflights are designed as a window – in the closed position – but when opened they create a glazed canopy and barrier in one.
They can be installed as an individual rooflight or in a bank to create a larger window and balcony.


roof terrace

Roof terrace

created where an adjoining structure is used to create an outdoor space, accessible from a bedroom or upper floor space. For example, the flat roof of a ground floor extension, porch, or garage.


What do the building regulations say about creating a balcony?

Below are examples of some of the matters that builders, homeowners, and designers should be aware of. This is not an exhaustive list but a good starting point. 

In almost all cases, the work to create a balcony will be controlled work under the Building Regulations and you’ll need Building Regs approval. The work is likely to be classed as a material alteration of the building as it may affect:

Below we discuss the more detailed regulatory matters for each balcony type. 

Juliet balcony

If the window is to be altered to make a larger window, then the work for the window is controlled under the Building Regulations. The increased size of opening may have a material effect on the stability of the wall and the new window (it is not classed as a replacement window) is classed as the provision of a controlled service or fitting. For these reasons and those mentioned above, the work is notifiable to Building Control.
Building control will want to know:

Will the balcony door be secure from break-in (not a building regulations consideration unless this is a new dwelling, but insurers may be interested)?

Hung, bolt-on and cantilevered balcony

As well as all the points made for Juliet balconies, the method of fixing the balcony to the building will be even more critical to make sure the platform is secure and can transmit loads to the building and onward to the foundations. Again, the work is controlled and will need to be notified to Building Control. You’ll need highly specialised advice and calculations from a suitably qualified and experienced structural engineer. They will consider:

Your architect will need to consider:

Stacked balcony

In addition to all the points above, for both a Juliet and Cantilever balcony, the design of the posts or pillars and the connections to the building will need detailed consideration. The work is controlled because it will be treated as a material alteration of the building because of the connections made to the existing building and the need to ensure the existing building can safely carry any additional loading.

Again you’ll need specialist advice from a qualified and experienced structural engineer. They will also have to consider:

Your architect will need to consider:

Loft rooflight balcony or Cabrio.

These systems are usually part of much larger loft conversion works and so the details should be supplied to Building Control as part of the conversion work plans etc. Specialist advice about the design of the roof to accommodate the rooflights should be obtained from a qualified structural engineer. The design of the rooflight balcony system should be supplied by the specialist rooflight manufacturer or supplier including any fitting kits to prevent water ingress.

As with the other types of balconies, the matters previously mentioned should be considered – particularly moisture protection, thermal insulation, safety glazing and barrier height/safety performance etc.

Roof terrace/balcony

These are often existing structures that are being renovated and upgraded. Usually the use of an existing roof as a terrace/balcony is not controlled work under the Building Regulations and it’s not notifiable to Building Control unless:

Flat roofs are typically only designed to take light loads from snow, wind, self-weight and occasional access for maintenance and repair. The roof surface is only likely to be designed to cater for protection from rain, snow, and damage from some occasional foot traffic. Changing the use to a balcony might cause the structure to fail because of heavier loads imposed by more people and furniture. In all cases the roof and supporting structure – any lintels or supporting beams over windows/openings foundations – should be assessed by a qualified and experienced structural engineer as being suitable for the use as a balcony/terrace floor before it is used as a balcony.

Like the other balconies, the alteration or creation of a new window or door to the balcony is controlled work and is notifiable to building control.

If you’ll be modifying the roof you need to consider: 

Work to alter the structure of the roof is classed as a material alteration, and possibly also classed as a renovation of a thermal element if the roof is above a heated or conditioned space. If the foundations require strengthening – by underpinning – this is also controlled building work. All of this work requires building regulations approval.

Some additional things to consider.

light hitting
damaged balcony