Loft Conversion Building Regulations - A Concise Guide

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When undertaking a new project the building regulations, as you would probably expect, are very in-depth and dense - but not to worry because here we boil everything down to the basics.

What follows applies to England and Wales and to a large degree Northern Ireland. But it should be noted that the building regs are different in Scotland.

Unless you are installing a basic storage solution by laying chipboard flooring than you must have building regulations approval for your project.

At this point it should be noted that the building regulations are not the same as planning permission and, in some cases, both the building regulations and the planning permission criteria must be complied with.

Of course keeping up to date with the latest changes in legislation can be difficult enough for professionals working in the industry let alone for the rest of us and two recent significant changes to be aware of are:

Changes To Permitted Development

Changes To Part L

So what is this legislation for?

The regulations are the minimum allowed standards of construction and design as laid down by the government and, for loft conversions, they fall into five main categories:

Structural Stability

For anything other than light solutions you will need to install new ceiling joists and will more than likely have to double them up.

That new room in the loft is going to have to carry some serious weight and the loft conversion building regulations insist that joists and load-bearing walls are strong enough to support that extra weight.

Its likely that you will also have to install new steel beams to support those new joists.

Another facet to structural stability is the roof itself and whether its structure needs to be altered to fit in your new conversion.

This is of course a complicated area but you can read more about it here.

Fire Safety

It goes without saying that the loft conversion building regulations on this point are very strict and rightly so.

The plans for your conversion must give plenty of consideration to fire safety and your design will need to take into account the new rules on fire doors.

Your new loft floors and walls must be able to resist fire for thirty minutes and glazed door panels must be made of fire-resisting glass.

Escape from the loft in the event of fire must be addressed with a full escape route provided by a protected stairway. It should be noted that escape windows in the loft are no longer acceptable except for certain bungalow conversions.

Mains operated fire alarms, linked to others in the property, must also be installed.


New loft conversions need rapid and background ventilation. Rapid ventilation simply means a window which is equivalent to 1/20th of the floor area.

If you are converting your loft to a bathroom then mechanical ventilation is also required which needs to extract 15 litres per second.

In addition the new roof void needs to be ventilated to prevent condensation and you may also need to ventilate at the eaves level and ridge.

There must also be a minimum air space of 50mm between the roof covering and the insulation though this may not be necessary in older houses with no roofing felt.


Probably the most important element, in both an aesthetic and practical sense, of your new loft conversion.

Getting the new staircase and access right will have a massive bearing on the success of your project but the loft conversion building regulations throw up a number of things that you will need to consider when planning your staircase to the loft.

Because of the importance of the staircase to your loft conversion there really is no quick way to sum up the relevant loft conversion building regulations.

So, take a deep breath, fill up the whiskey glass, get the wife/husband/partner to massage your back and click here for a detailed discussion.


Again you don’t really need to be told that this is important and why would anyone go to the trouble and expense of converting their loft and then not insulate it?

Nevertheless the loft conversion building regulations insist that your loft, including new internal walls, must be fully insulated.

As we have stressed throughout this page, obtaining approval for your conversion project is an essential step to ensure your project meets health, safety and design standards.

The application should be made before work begins and there are two main options for the application, either making a full plans application or by giving a building notice.

A possible third option is to use an independent independent inspector.

Full Plans Application

The recommended route. You need to submit copies of your plans showing construction details along with a completed building regs application form.

You will also, of course, have to include a fee with your application. This is a necessary evil which must be tolerated (a bit like the mother-in-law). Fees may vary but you’re probably looking at a few hundred quid.

Once the council have received your loft conversion plans their building control officers will check that they meet the building regs and will then issue a notice of approval.

If there is a problem the building control officer will ask you to submit revised plans before approval is granted.

Once you have your notice of approval work on that brand new loft conversion can begin.

The building control officer will make regular inspections to ensure that the work is carried out in line with your approved plans and loft conversion building regulations application.

Building Notice

Easier than making a full plans application but going down this route could lead to problems later on down the road.

This kind of application doesn’t require any plans to be submitted, just an application form and a fee (same charge as for the full plans application) – basically all you are doing here is telling the council that you will be carrying out work on your loft conversion and that you will comply with the loft conversion building regulations.

The building control officers can ask for detailed plans if they wish but that is unusual.

By giving building notice no actual approval is issued by the council so there is more onus on you to ensure that the building regulations are met. Site inspections will, of course, still be carried out.

A very important point to note is that under the building notice procedure the local council are not obliged too, in other words they won’t, issue a completion certificate.

Ready To Submit That Application?

Unless you know the loft conversion building regulations inside out make a full building regulations application. And even if you do know the building regs backwards – it may still be best to submit your full plans. The councils building control officer is in effect your quality control expert.

He will ensure your plans are up to scratch and will also inspect your work, or that of your builders, for you. This can help prevent all sorts of problems.

Another point in favour of making a full plans application is that if you enter a dispute with the council i.e., disagree with their decision you can ask for a ‘determination’ from the Office of the Deputy Prime Minister or Welsh Assembly to settle the dispute – this service is not available if you simply give building notice.

How Long Will It Take To Get My Approval?

The government guidelines issued by the Office of the Deputy Prime Minister, state that the local council must give you “a decision within five weeks or, if you agree, a maximum of two months from the date of deposit.”

Off course, if the council believe your application doesn’t satisfy the building regulations then they will reject your application and will not grant approval.

If your application for loft conversion building regulations approval is rejected click here.

So When Can I Start Work?

If you have taken the time and trouble to make a full plans application it is best to wait until you have received your notice of approval.

But, if you wish, you could begin work by notifying the council at least two days in advance once you have made your application.

Not to be recommended if you think there may be a problem in satisfying the building regulations.

Under the building notice procedure you can begin work after two days as there are no plans to consider.

When Your Loft Conversion Is Finished

When your loft conversion is finished, the staircase is in place, the new loft windows fitted and the fire precautions satisfied and the council are happy that the work meets all the building regulations they will issue you with a certificate of completion.

Make sure that this certificate is kept with the original approval notice as these pieces of paper will be vital when it comes to selling your property. They are your record that your loft conversion has been build well and in accordance with the building regulations.


You must state in your initial application that you want a final completion certificate when the work is finished. Sounds ludicrous but don’t forget.

For more info see the related pages below

How To Obtain Retrospective Approval

The loft Conversion Building Regulations - A Case Study

The Difference Between the Building Regs And Planning Permission

The Plans Needed For A Building Regs Application

The Building Regs & Headroom

A Readers Question About The FCC

Some Notes On Safety

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