Building Regulations for Windows and Doors

Author: Chris Hogan

The building regulations that apply to windows and doors are numerous but many of them can be adhered to simply by buying what you need from a mainstream supplier. Look for companies that can prove compliance and registration with a recognised scheme such as BSI, CERTAS or FENSA as they can deal with the certification and the Local Authority approval on your behalf.

The areas covered by the regulations are:

Thermal performance
Safety
Means of escape
Air supply and ventilation

Some of the regulations, such as ventilation, thermal efficiency apply to how the windows and doors are constructed, while means of escape and fire safety are more about how and where the windows and doors are fitted. General safety can fit in either category.

Thermal Efficiency

Energy efficiency is a hot potato at the moment and the government has tightened up many regulations in this area in recent years. The regulations regarding the U-Value, the amount of heat allowed to pass through the glass and framework of a window or door, are complex. There are also different ratings depending on whether the windows and doors are to be used in an extension or as replacements in an existing dwelling.

Most manufacturers will be aware of these ratings and their use, and will be able to sell you compliant units. If they don't seem to understand the question or gloss over it then it's safer to walk away.

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Air Supply and Ventilation

It's the existence of air supply and ventilation regulations that account for the little vents with closable covers that began to appear on double glazing units a decade or so back. It was discovered that having completely airtight rooms, something that was quite possible with modern double-glazing and the focus on draught-proofing that we have today, brought its own hazards.

The amount of ventilation required will differ depending on the way a room is being used, with bathrooms and utility rooms, for example, requiring more ventilation capability than bedrooms or lounges.

Your situation may be slightly different. ask a question below ↓ and our editorial team will reply with our advice.

Safety Issues

Safety is a widespread issue too. Firstly there is the use of safety glazing, which must be used when the glass is installed in what the regulations refer to as a 'critical area'. This is defined in the regulations as:

Any glazed area within a window below 800mm from floor level
Any glazed area within a window that is 300mm or less from a door and up to 1500mm from floor level
Within any glazed door up to 1500mm from floor level

Again the manufacturer should be able to comply with this without any problem.

Other safety issues regard the placement of the doors and windows within the extension, usually with regard to escape from fire. It is regarded as good practice to install escape windows, i.e. those that can open wide enough for people to easily pass through, on the first floor and any higher than that. Fire regulations also govern the thickness and fire resistant nature of internal doors.

Bay Windows

Finally one tricky one to note is that adding a bay window to an existing home will be treated in planning and building regulation terms, as an extension. So if your extension has bay windows and you want to convert some in the current house to balance the overall design, you will have to get building regulation approval for that as well as the main extension.

The Next Step

Now that you have read through the advice above, you might want to put it into practice. Our Planning Permission Checker lets you tell us about your planned extension and find out whether you need planning permission or can build under permitted development. Try it now →

57 questions

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ExtensionBuild Editor 23/05/2026 at 9:15 am

@Viva Fenester Glad it landed well, Viva. One thing worth flagging that often trips people up: Part L now requires a U value of 1.4 W/m²K or better for replacement windows, and Part F means you'll likely need trickle vents fitted too. Building Control sign off is a must unless you're using a FENSA or CERTASS registered installer who can self certify. Worth budgeting for that bit of paperwork early rather than scrambling at the end.

Viva Fenester 11/12/2024 at 7:23 am

The article on building regulations for windows and doors provides important insights for homeowners planning to extend or remodel their homes.

Liffis 24/01/2020 at 5:32 am

I am interested in purchasing a new house. The house I like is the only house that does not have glass panels above the front door. The door is solid pvc with no glass side panels or windows. Builder originally agreed to replace door with glass panel and then changed his mind. I feel that the hall will be dark. Is there any regulations stating that there should be natural light in a hallway.

Jshore95 03/08/2019 at 7:52 am

Hi, the approved basic plans on my house have a patio doors approved for the rear end. The architect plans have changed the patio doors to a engender area of glass with windows above the doors letting more light through. The architect has advised it shouldn’t make a difference to planning. The view from the rear is private and overlooking no other houses etc. Do you think it will effect planning/building regulations l?

mouledrums 02/04/2019 at 4:01 am

Hi, I have some 'used' triple glazed units that were specialist made for acoustic insulation. Each unit has three different thicknesses of glass - 4, 6, 8mm and are about 1.2M square. The units are about 25mm because of the air gaps between panes to help acoustic insulation. The original plan was to use them in a recording studio build which is now unfortunately not going to happen.

They're a few years old - I acquired them 4 years ago and they were unwanted by a manufacturer who's project was cancelled and they were going to get smashed! I got them for free.

Just wondering if it would be possible to use them in a proposed kitchen extension on my home. It's a modest extension - 4.3M(w) x 2.3M(d). It's going to be single storey with possibly a new vellux (or two) in the ceiling. The idea is to use a couple/3 of them on the external wall to the garden, or (if I can get a frame to fit), a 4x4 configuration in a fixed timber frame as a kind of 'feature wall'. There's a joinery company I've used before that make great timber frames that can make them compliant with regs.

I plan to 'over-egg' the new build in terms of insulation etc. The house is aprox. 18 years old, so requirements weren't as good as now and I want the extension to have as little thermal effect as possible - ideally improving the performance of the kitchen in reality.

I've contacted the owner of the company (a former neighbour of mine) in the hope that they might have some performance specs from when they were commissioned but I expect that to be difficult.

IS there any way to test the performance of the windows to comply with regs & see if I could use them?

Any advice gratefully received!

Bd261018 20/02/2019 at 11:53 pm

Hi , I’m looking to buy a house in which the seller has patio/French doors in the upstairs bedroom but there is no safety fence or balcony leading to it. So if you were to open them you could fall straight out. I have small children. Is this legal to have as it’s a door on a higher level?

ExtensionBuild Editor 17/05/2017 at 11:00 am

We don't see what not as long as they comply with Building Regulations. You might want to look into how you can improve the insulation qualities of the doors.

brew85 15/05/2017 at 5:22 pm

Hi, I'm planning a Side Return kitchen extension and would like to re-use the original victorian french doors that would have led out previously to the empty space we are now filling with the extension. Would we simply be able to have the (2) doors resituated into the new extension? They're currently single glazed doors and have fanlights above each door.

Dave 20/04/2017 at 7:45 pm

I have had upvc windows and French doors fitted. The installer has not fitted a sill with the French doors and said I don't need one. Is this true. Thanks

ExtensionBuild Editor 14/02/2017 at 2:33 pm

We're not sure about this as the regulations seem to suggest that fire safety glazed doors are acceptable. You need to ask for a second opinion on this...or ask your building inspector to provide a copy of the regulations he/she's referring to.

Bridgy 13/02/2017 at 2:28 pm

Building inspector says that i need a non glazed door from my hallway to the kitchen. Currently it is a 4 panel timber door with the two upper arched panels glass. Can you advise please

ExtensionBuild Editor 15/12/2016 at 12:22 pm

We can't advise on this kind of thing as we don't have full details of your situation. Your council's building regulation officer will be happy to advise you.

BILL 14/12/2016 at 1:28 pm

Hi all. I am doing a garage convertion.( lounge/small kitchen for my dougter /baby ( Rents to high for her outside ) Budgets tight for heras well. Can I use good quality up to date ( USED ) upvc Windows and doors as per plans ??!! Help

Jen 30/10/2016 at 4:10 pm

Looking at removing back door and having upvc french doors instead with each door opening independently. Are there any pitfalls to this?

ExtensionBuild Editor 11/10/2016 at 2:29 pm

The internal door or the external one>?

Patsy 10/10/2016 at 7:31 pm

Hi, I have a 3 bed bungalow with a 2 bed bungalow attached. There is a rear door in one bedroom and in the small kitchen. I would like to remove the kitchen door is this permitted?

Many thanks

Pat

none 07/10/2016 at 3:09 pm

I have a rear door to my house that only opens 45% it opens in to an allie I have a disabled wife how would find it hard to use in an emergence dose this comforme with building regs

ExtensionBuild Editor 05/10/2016 at 10:48 am

We see no reason why a sliding door would not pass building control regs, yes it would need to be fire rated, but you can buy fire rated internal sliding doors. Give your building control officer a call, they're normally happy to advise on these issues before you go ahead and submit plans.

Bob 04/10/2016 at 7:52 am

Hi,

We are looking to extend into the loft and want to maximise the space where we can. We are considering putting sliding doors into the bedroom so we don't have a door in the way all the time. Do you know whether this would pass building control? Would the door need to be fire rated? Is there anything else we need to consider?
Thanks

crankysan 16/09/2016 at 10:26 pm

Hi . Moving house soon and would like to put in sliding upvc double doors where the bedroom window is onto the garden. Would I need planning permission to convert ?Thanks

SteveO 26/07/2016 at 10:58 am

We have a Georgian house with existing up floor side windows, that were obviously put there when the house was built 120 years ago.They do overlook the next door, so do they need obscured glass.

ExtensionBuild Editor 06/05/2016 at 10:36 am

It might be useful to ask your local building control team, in general we think it should be fine as long as they bear the CE Mark and you know that they will comply with British Standards.

Thonitoes 04/05/2016 at 2:41 pm

Hello

I want to import my own windows and doors PVC /Alu direct from the manufacture from Romania - I have a great contact working in the industry and the savings are huge.
They have certifications but not ones here in the UK - will I be able to use them - they are European certificates?

Thanks

ART 11/01/2016 at 8:19 pm

Can you tell me please what is the current minimum external and internal door height required by building regulations for all dewlings. I'm interested to know if it caters for the growing, in height, population, or are the building regulations being "heightest" (being prejudice against the tall ones) by not have enough head clearance for them.
ART

ExtensionBuild Editor 11/12/2015 at 2:38 pm

What did your planning department advise? It's usually a condition of planning for new builds/extensions but this one may have been in place for some time? Was there any information provided in the seller's pack etc?

Matt 11/12/2015 at 9:54 am

Hello, I have recently bought a house and the neighbouring detached house has two large ground floor windows (side elevation) which are fixed but not frosted. These windows overlook my garden and rear back door and kitchen. There is also a single storey extension with a single frosted window which is not fixed. When open the window oversails the boundary line into my property. After enquiring with the planning department they have no planning history on this neighbouring house. Am I within my rights to tell them the windows need changing to fixed, frosted windows?

ExtensionBuild Editor 13/10/2015 at 2:49 pm

We can't find any information about minimum door heights on existing buildings. We'd expect your builder and architect to be aware of this. Why not give your building control office a call and ask for general advice on door heights to be sure.

Jenlee 12/10/2015 at 3:07 pm

We have an old storehouse with very thick walls. We have just finished replacing a utility room at the end of the house. In the same place but wider. All the regs have been followed in the rebuild. But when an inspector came out he said the adjoining door may need to be highered.
It has a huge stone lintel and would be a big job. Nobody mentioned this. Not the architect or the builder.

Jenlee 12/10/2015 at 2:55 pm

We have just replaced a utility room on the end of our house. We have made it twice the width and had plans drawn up. Our builder has filled the building regs to the letter. Half way through an inspector came to check if the drains were ok. They were. At the finnish of construction an inspector came and said we may need to higher the outer door leading into the extention. The building is 130 years old with a huge stone lintel above the door. Nobody mentioned this. Not the architect, the builder or the first inspector. I wounded have even attempted to replace the out building if I had known. Is there a legal height for existing outer doors in old buildings. Regards

adam 11/09/2015 at 7:32 pm

Are there regulations around how much weight a steel window well cover should hold? Our builders just fitted one and it has fallen in on itself after i stepped on it lightly. he did warn me not to stand on it, but the fittings he put in place to hold it up were just screws, not the giant bolts with o ring ends as before. Have i been robbed or is there no weight threshold? Building regulations said we needed to a minimum width round the grid, so someone could trap thier leg down the side, but someone standing on it and it falling in on itself seems like more of a risk. Advice would be greatly appreciated.

BristolBoy 04/09/2015 at 1:38 pm

Good afternoon,

We recently engaged with a company to install a catflap into a sliding glass door in the rear of our house (a kitchen extension).
The installation was not as we expected as the cat flap sticks out too far to permit clearance of the fixed part of the window/door.
As such, the glass door now slides open only roughly half as far as it used to. (I cannot get through without turning sideways -- and I am not sure we'll be able to get patio furniture through the doorway). A real nuisance and not to our expectations.
Is there a minimum size of opening for a back door? I am concerned that not only has he botched the job, but he has also introduced an alteration which might not meet building regulations.
Thanks,
JT

ExtensionBuild Editor 27/08/2015 at 10:57 am

We don't think there are building regulations relating to obscure/frosted glass in downstairs windows, it's just something people prefer for privacy. Contact your local planning office to be sure.

ExtensionBuild Editor 27/08/2015 at 9:31 am

Your building control officer should be able to tell you whether your existing door/windows meet the relevant criteria. Give him/her a call for advice.

Beano 25/08/2015 at 8:33 am

We are purchasing a new build property by a local developer The bathroom and ensuite windows, that will be at ground level due to the split level nature of the building, has no privacy / frosted glass installed. Is this against building regulations?

smallboybob 24/08/2015 at 7:24 pm

I've just become aware of the new building regs Part L for doors/windows which came into force in 2013/14. I have just had planning permission approved for a new porch and side extension but intended to use my current uPVC front and back doors and some of my uPVC windows (all approx. 10 years old) on the new porch and side extension. Will I now have to factor in the cost of purchasing new uPVC double glazed doors and windows instead?

Simon 21/07/2015 at 2:16 pm

we wish to put a conservatory on the back of our bungalow. To achieve this we would need to create a corridor by making one bedroom smaller and the put in a new door out of the rear wall into the conservatory. Would we need building regs for this??
Thanks

ExtensionBuild Editor 12/06/2015 at 12:22 pm

@Row. Your building control officer will be able to help you with this. It really depends on the construction of the remaining extension, e.g the fire safety implications, insulation/energy requirements and security.

Row 08/06/2015 at 10:57 pm

I am having a ground floor extension at the back of the house. The existing patio doors are coming out. Can i leave this open or do i have to have doors fitted to replace them
ThanksP

ExtensionBuild Editor 17/03/2015 at 10:44 am

@DebLan. Contact the builder with your concerns. Ask for details of the window quality etc - new builds should be sound tested under Part E of the build regs requirements. The developer will be in the best position to get this remedied.

DebLan 13/03/2015 at 8:43 pm

Have moved into a house built by a well known national builder who sub contracted
out the installation of the windows and doors to a local company who manufacture their own product.
We have never experienced such poor quality of sound resistance in windows in any house we have
Lived in before. When windows and vents are closed we can hear the conversations of people outside and have been woken by a baby crying in a house nearby. It is a development and houses close, but cannot believe this can be acceptable. None of the windows bear a kitemark -should they- or is this an indication of poor quality? We know there are regulations around thermal thickness etc but is there anything in place regulating sound resistance?

ExtensionBuild Editor 10/02/2015 at 2:08 pm

@JJ> This probably wouldn't need planning permission but you should read the building regulations regarding internal doorways to make sure you compy. Your building control department will be able to help you.

JJ 06/02/2015 at 9:46 pm

Recently had a rear extension built (Bungalow) with upvc double glass doors leading into the dining room. We now would like to change these doors to a single one. Is this possible?

ExtensionBuild Editor 24/11/2014 at 2:12 pm

@roza. Check with your local building control depart. You will also need planning permission for a balcony etc .

roza 21/11/2014 at 8:54 pm

I ordered by mistake French door that open out ward and want to know can I correct my mistake by having a balustrade/ balcony that accommodate the with of the door. It is on the first floor of the house. Will it pass building regulation in terms of health and safety.

Dickie 31/10/2014 at 10:05 am

a front door 2ft wide would this be allowed

Magoo 22/09/2014 at 1:37 pm

I have been advised by a replacement window company that I may not be able to change the sliding door on the front of the property which provides access to a porch because the replacement door will have a smaller 'walk through' than the inner front door. (-60mm) this is in accordance with building regs, I am unable to find any detail in this regard. Any help and advice appreciated.

ExtensionBuild Editor 15/07/2014 at 12:29 pm

@KJDavies. You do not normally need to have planning permission for new windows in a side elevation at ground floor level unless there were any conditions already in place to the contrary. New upper floor windows to side elevations need to be of frosted/opaque glass. Check with your local planning department to see whether there are any conditions in place in the locality.

gent 14/07/2014 at 5:31 pm

I live in a 1939 detached bungalow the bungalow next door has been bought an in the process of being renovated by the new owners. they have just made an opening in the side wall to install a new window which is now directly facinf our lounge window ,is that allowed regards KJ Davies.

colsey 25/02/2014 at 7:19 pm

Hi i need to brick my back door up in my kitchen to create space but also open the dinning room window up to a French door the dinning room new door will be two feet away from old kitchen door but means the fire escape will be in another room is this allowed

bopala 11/10/2013 at 8:46 am

I live in a semi sheltered bungalow owned by a housing association what are there responsability to internal Fire doors
Regards
Barry

Rid 04/07/2013 at 5:33 pm

Could you tell me is there a regulation governing the height of front door sills

Acko 20/10/2012 at 10:16 am

Do internal office doors now have to have glass panels in them to see in and out in the event of an office fire elsewhere in the building, so it can be seen?
Is this mandatory?

stu 18/09/2012 at 6:56 pm

How many fire escape windows do you needs if you are replacing old for new UPVC window and doors?

fi-g 12/09/2012 at 4:25 pm

I know that there are width requirements for internal doors in new-build so that wheelchair access is possible - is it the same for an extension or can I put in standard 90 cm doors? Thanks

Dave 11/07/2012 at 3:45 pm

I have a cottage with restricted room inside from the front door, i would like to know if i can have the door opening outwards rather than inwards, are there any restrictions as it would create far more space inside. The door opens directly onto the kitchen.

bo 25/05/2012 at 7:25 pm

I have been told by my home report surveyor that the door into my living room does not meet the building regulations as the eight panels of glass do not have a kite mark on them is this correct

regards

Breandan

PASO 29/03/2012 at 3:22 pm

Can I brick up kitchen door leading into garden? We have a door in hallway leading to integral garage witch also has side door, also have patio sliding door leading into conservtory witch also have opening doors

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