Rules and regulations when planning a garage conversion


The building notice

Prior to commencement of any works a building notice should be submitted to the local authority building control department at the council offices.

What this entails is a form detailing the works to be carried out along with a date of commencement. For the purpose of a garage conversion detailed drawings are not usually needed as the work is pretty straightforward. However, if planning permission was required due to any major alterations such as renewing the roof structure or extending the building then drawings detailing the structure may be required.

There is a fee involved, usually based on a percentage of the total price of the work. Lets say the job was worth £5,000, the fee may be 5%, £250. It pays to keep the cost down J Most councils have a website where you can check their scale of fees. Work between £0 - £2000 may incur a fee of around £80, £2000 - £5000 may be £200 and so on. There is generally no specific set rate for a garage conversion, its all down to what the job entails.

Once in receipt of a building notice the building control office will usually issue a set of guidelines specific to the type of works. This will usually contain all the relevant ‘u’ values (level of insulation) for the different surfaces and accepted construction methods along with acceptable footings etc.

During the course of the work the building inspector will need to visit the site periodically to inspect certain aspects prior to them being covered over with other materials. Things to get inspected are :- structural alterations (footings, walls, lintels, roof), first fix joinery (structural), insulation (usually on or just after installation), possibly even first fix electrical work depending on the person carrying out the work, soundproofing, fireproofing and any other ‘proofing’ than cannot be accessed or seen once the build is complete. Anything that can be seen or accessed once complete will not need an intermittent inspection as its existence can be verified on final inspection where the inspector will need to see copies of any required certificates such as electrical work. Remember to leave the ‘k glass’ stickers on your windows until the inspector has seen them!

Remember that only when the building inspector is happy that the work has been carried out in accordance with current building regulations and he is in receipt of any relevant documentation will he issue a ‘completion certificate’. Failure to call building control on time to view a portion of the job which is to be covered over (plasterboarded etc) or failure to obtain an electrical installation certificate may result in you having to rip off any coverings just to prove that you’ve installed the correct depth of insulation and the first fix is satisfactory. Failure to obtain a completion certificate will leave you with problems when / if you come to sell your house as you will need to prove that any work carried out by yourself is of an acceptable standard. (back to ripping coverings off again)

What is a ‘u’ value, exactly?

Simple really, the ‘u’ value of a substrate, be it brick, block, timber, polystyrene or an entire structure such as a flat roof is a measure of how much heat is lost through it in one hour over a square metre. Measured in watts. The lower the u value, the better the level of insulation. Adding insulation to an existing structure such as a single skin wall will significantly lower its u value.

The Kyoto agreement

The Kyoto agreement or protocol was signed by the British government at the earth summit in Japan. It basically states that Britain agrees to reduce carbon emissions to pre 1990 levels by the year 2010. Its all about global warming and the conservation of fuel and power, hence the relative approved document (approved document ‘L’). This affects new buildings as well as old, and guidelines are set out to achieve this.

Burning fuel produces carbon emissions. The way to reduce these emissions from buildings is to reduce the amount of fuel burnt, therefore better insulation is required to hold in the heat. Its that simple.

What this means in a practical sense is that every so often new legislation is brought out giving minimum requirements for insulation. What was once considered excessive is now considered inadequate. Loft insulation for example. What was once considered more than enough (150mm of isowool) is now considered woefully inadequate and 250 - 300mm is the new norm.

This does make a massive difference to the heating requirements of a building and should be taken into consideration when calculating heat loss for a room to install the correct sized radiator.

Typical specifications

There are specific documents issued by the government detailing the requirements for things such as insulation, fire regulations, damp / moisture control, electrical standards, glazing standards and more.

For more information please search the internet for approved documents relating to Building regulation and approved documents. Ultimate handyman no longer links to any Government website as they keep moving or deleting the pages which leaves us with hundreds of dead links on our site. We cannot put a copy of the approved documents on this server as the documents are regularly updated and so you could be viewing an out of date document.

Some are obvious common sense. Some are not and care should be taken when interpreting them. Building control will also issue things like ‘u’ values on receipt of the building notice and it is worth noting that some if not all will be of a higher standard than those given in the approved document ‘L’ 2006 issued by the government. This is in line with the Kyoto agreement to continue to improve carbon emissions by 2010.

Typical legislation encountered with a garage conversion is given below.


Typical values are given in Wm2k. Taken from approved document ‘L1b – conservation of fuel and power in existing dwellings’ April 2006

Walls0.35 likely received from building control0.30
Flat Roof0.25 likely received from building control0.20
Floor0.25 likely received from building control0.20
UPVC Windows2.00 likely received from building control2.20
Metal Windows2.20 likely received from building control2.20



Fire regulations

Should the new conversion be used as a workshop or business where the likelihood of fire is high then special ‘fireline’ fireproof plasterboard should be used, the specification will be given by the council and may well consist of 2 layers of board with a plaster skim finish. Any exposed steelwork such as universal beams (rsj’s to the layman) should also be clad in fireline board.

With repect to fire escape egress the following guidelines need to be followed :-

Rooms such as bathrooms, wc’s, and utility rooms are exempt from egress regulations.

All other habitable rooms need either – access to a corridor / hallway leading to an outside exit or a fire egress window of minimum size, namely 600mm opening width with a total area not less than 0.45 square metres. Hinges to be egress type. (easy clean hinges are accepted) so the window can be opened fully, hinged at the corner. Standard friction hinges found on standard upvc windows are not acceptable. Non locking handles to be fitted although child resistant stays are accepted provided a catch can be released to facilitate the opening of the window in the event of a fire. The maximum height of the window above floor level shall be no more than 1100mm. The external of the window should also facilitate escape and should not be an enclosed space smaller than the face of the building. An alleyway with locked gates either end is not acceptable.



In the event of any part of the new conversion being a wc or ensuite/bathroom then a extractor fan is needed of 4” diameter with a 15 minute run-on timer working off the lighting circuit. In the event of the new conversion becoming a kitchen then a 6” fan may be required or the use of an over hob extractor. All must be vented directly to the outside and not into any roofspace.


Damp / Moisture control

A damp proof membrane may need to be installed under the floor or a vapour barrier to any insulated walls/ceiling to combat condensation. This all depends on the method and type of insulation.


Any new circuits added to the existing supply need certification by either building control or a NIC/EIC registered ‘part p’ qualified electrician. This involves the testing of all new circuits and a certificate of compliance issued on completion. Building control certification avoids the need for a part ‘p’ qualified electrician but will need inspection by the council instead, both first and second fix.


Any modifications or installation of gas appliances need to be carried out by a corgi registered installer. Oil fired appliances need an OFTEC installer. Again certification is required for final completion.

The party wall act

Not just any wall you can hang balloons and streamers on but any wall which is also part of a neighbouring property or any new wall you propose to build on a neighbours boundary line. You will need to notify the neighbours and in some instances building control will have a say in any footings or excavations close to a boundary line.


Should you be intending to use the conversion as a business premises then different fire and access regulations apply. Fire alarms and wider doorways with access ramps for the disabled may need to be installed.