Loft conversions: what are the building regulations?

Whilst a loft conversion may not require planning permission, your project will still need to comply with building regulations...

A loft conversion is a fantastic way to increase your living space. While you may be able to carry out the work without planning permission (permitted development may be enough), your loft conversion project will still need to comply with building regulations.

Building regulations are statutory requirements for all building projects, so you are legally obliged to ensure your loft conversion adheres to these rules.

When you work with CR Designs, our experienced architects and structural engineers can prepare plans and building control drawings that incorporate the regulations into the loft conversion process.

Staircase regulations:

Stairs are an integral part of any loft conversion and come with their own set of regulations. Your building control drawings will need to consider:

Width and height:

When designing your staircase, it’s important to remember that you need to be able to get furniture up to the loft space via the stairs. There are also fire safety considerations (more on this in a moment).

What’s more, there needs to be a landing at both the bottom and top of the stairs and the width and length of these should at least be the width of the stairs.

Whilst there is no minimum width for the staircase itself, it’s generally accepted that you should keep to at least 750mm. However, in the case of loft conversions this can be pushed to 600mm.

Rise and going

The vertical part of the stair (known as the riser) should be a minimum of 150mm and maximum of 220mm in height.

The part of the stair you step on (known as the going) needs to be at least 220mm and no more than 300mm.

Positioning and pitch

The top of the stairs needs to be positioned at the highest part of the loft, with a pitch or angle nor more than 42°.

Head room:

There needs to be 2m of clear headroom above the stairs. This headroom must be constant throughout the whole staircase, however regulations allow this to reduce to 1.8m at the lowest point if the stairs are under a sloping roof.

Handrail, balustrades & spindles

Your building control drawings must include a handrail between 900mm and 1000mm high.

Balustrades at least 900mm light must be added to any staircase that is exposed and are higher that 600mm.

As a safety precaution, stair spindles must be installed with a maximum distance between them less than 100mm.

Non-traditional staircases

If space in your loft conversion is limited, you may be able to opt for an alternating tread or paddle staircase, a fixed ladder or a spiral/helical staircase.

Each of these types of staircases come with their own set of regulations, so your architect and structural engineer will consider these in your building control drawings. 

Fire safety regulations

There are a number of rules concerning fire safety that must be addressed in your loft conversion building control drawings:

Fire doors:

Any existing loft doors will need to be replaced with fire doors. The ideal door should be able to resist heat for at least 20-30 minutes.


Like the fire doors, the staircase installed in your loft conversion must be fire-resistant for a minimum of 30 minutes. This also applies to any glazing you have within the stairwell. 

Smoke alarms:

Building regulations require you to install a smoke alarm into all new spaces created by the loft conversion. You must also ensure that they are linked to the mainline.

Fire containment:

Should a fire occur, your loft conversion must have walls are fire-resistant enough to limit the damage caused.

Floor joist regulations

If you are converting a loft that hasn’t previously been used as living space, then the chances are the existing joists will need to be replaced.

There are rules to follow and your structural engineer will be able to calculate the size of joist that is required when preparing your building control drawings.

Insulation regulations

Installing the correct insulation will limit the amount of heat your loft conversion loses through the roof.

The type of insulation you need will depend on whether you already have insulation in your roof space and if so, how effective it is.

Other features of your loft conversion that must comply with building regulations

The above list is by no means exhaustive and there are many other regulations that you will need to follow to ensure that your loft conversion is approved by building control.

When preparing your building control drawings, you and your structural engineer will also need to consider:

  • Doors and windows
  • Drainage
  • Electrics
  • Walls and roofing

Our building control drawings and structural specification packages

If you wish to convert your loft into living space then our team of experienced architects and structural engineers can turn your ideas into reality.

We will prepare concept design and planning drawings, aswell as building control drawings and structural calculations within weeks. We will then submit your plans to the council and act as your agent for the duration of the project.

Our comprehensive and affordable design packages are suitable for all loft conversion projects, not to mention extensions, garage conversions and new builds.

Find out more about our building control drawings and structural specification packages.

Convert your loft with CR Designs

To discuss how we can help transform your home, get in touch today.

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