Extending Your Home – Planning and Permitted Development


With a growing family, there may come a day when the headcount in your home exceeds the bedcount in your house.  Even if that’s not the case, you may well question why you have to shift stacks of boxes of Duplo and Playmobil around just to get a decent view of the TV (assuming you’ve successfully dealt with the bedtime ‘routine’ and made it to the sofa, without falling asleep yourself).

Alternatively, your fabulous period home, may include not so fabulous period features, such as a kitchen barely large enough to swing a (Jellybean) cat, that isolates you from the rest of the family. So whether you’re working meticulously from Annabel Karmel (first child) or pureeing last night’s leftovers (third child), chaos may be unfolding in the ‘other’ room, or worse still… suspicious silence!

If, like us, moving to a larger house would mean either a crippling mortgage, or leaving the local community that you’ve vowed never to depart, then you’ve probably contemplated extending your home. Even as a RIBA Architect, my own experience of being the ‘client’ was occasionally challenging, though living back at my mum’s with toddler and heavily pregnant wife (and eventually newborn) didn’t help!

Eight years on, we’ve managed to stay in the area, had another child and hosted countless children’s parties in our extended family home. Of course we’ve still managed to fill more space than we ever thought we needed, but it still works and we can’t imagine living as we did back then.

It’s not always straightforward and meeting clients today, it’s surprising how much confusion surrounds the planning process at the domestic level, despite government efforts to simplify it. So I’ve tried to put together a brief guide to this topic. Apologies if it’s a touch dry… unfortunately the nuts and bolts of planning are precisely that.

Remember planning is merely the what you are allowed to build; the how you build it is another topic, as is the much more exciting design process… stretching the what to its fullest possibilities and tailoring it to your needs. However, understanding the planning process is an essential, if dull, first step.

I hope to write more on the more exciting aspects of extending your home, at a later date, but if you need any further advice, feel free to contact me via www.ndarchitecture.co.uk

Whether you feel you need an Architect or not, it’s certainly worth having expert advice up front.

Do you know what you want?

The first question I ask people is generally ‘how long have you been here?’ It takes a while to realise what your needs are. It’s usually not advisable to pick up a sledgehammer along with the keys from the agent on completion day, although stripping seven decades of wallpaper can be cathartic. We tend to use our homes differently from season to season. For example, you might want to create a huge light open ground floor for summer parties, only to realise that you’ve formed a sterile box for the winter evenings, with no escape from the day that’s just past.

It’s OK to take your time to adjust and figure out what you need.

You definitely need more space and you don’t want to/ can’t move. Then you need to extend… right?

Not necessarily. Every house is different. Your house might already have plenty of square footage, that’s poorly used. Even extended houses, when badly planned, might not deliver what you’re after. Internal reconfiguration, particularly of larger, broader, between the wars and mid- 20th century houses, may solve your spatial problems, without the need to extend.

Failing that, you might not need to extend over the whole of a postage stamp garden in order to deliver a great family living space. You might be able to extend less than you first imagined necessary.

Extend smartly and efficiently.

What is Permitted Development?

Permitted Development (PD) allows you to carry out certain works, without planning consent.

It is, however, advisable to obtain a Certificate of Lawfulness, when going down this route, which will demonstrate to future purchasers that the works are authorised. The most common works carried out under permitted development are Loft Extensions and Single Storey Extensions. So long as your project complies with the objective rules, you can simply crack on and do the work (in theory).

There are a number of criteria to be considered other than listed below, so I’d still advise anyone that is considering this less formal approach to contact an Architect, when going down this route. However Broadly speaking the main rules are as follows:

General Exclusions

  • This does not apply to Listed Buildings, Areas of Outstanding Natural Beauty, World Heritage Sites & National Parks;
  • Conservation Areas allow for Permitted Development UNLESS they have been specifically excluded under an Article 4 Direction… contact your Council to find out if this is the case;
  • You have no permitted rights in a flat;
  • Works not covered by Permitted Development may still be acceptable, but a full planning application will be required.

Ground Floor Extensions


  • The standard permitted development rights at ground floor, subject to the above, are 3m (terraced/ semi-detached houses)/ 4m (detached houses);
  • The 3m/4m is measured from the original (or pre 1948) line of the house… if your house is staggered, then the 6m/8m line will stagger accordingly… it’s not simply 6m/8m from the furthest point of the house.
  • The maximum height of the eaves (within 2m of the site boundary) is 3m taken from the surrounding ground level.

Loft Extensions

  • Your PD rights for loft extensions are based mainly on volumetric calculations, namely:
    • A volume allowance of 40 cubic metres additional roof space for terraced houses;
    • A volume allowance of 50 cubic metres additional roof space for detached and semi-detached houses

The proposed volume will include existing post 1948 roof extensions at your property.

  • Additional criteria:
    • Nothing to the front of the house (or side if this faces a road);
    • No extension to be higher than the highest part of the roof;
    • Materials to be similar in appearance to the existing house;
    • No verandas, balconies or raised platforms;
    • Side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor;
    • Dormer extensions to be set back, as far as practicable, at least 20cm from the original eaves;
    • The roof enlargement cannot overhang the outer face of the wall of the original house.

Even if you extend using your permitted development rights, obtain a certificate of lawfulness to save hassle when selling.

Someone told me I can extend 6m/8m from the back of my property at ground floor level …

This is still a hot topic, although the rules have been the same since 2008, and have now been extended until 2019. This is known as ‘Prior Notification’ whereby you consult your immediate neighbours (side and back), but no one else is consulted on the proposals.

The detail of this is complex, so again I’d advise anyone that is considering this to contact an Architect, when going down this route. However, summarising:

  • This is dependent on your immediate neighbours assenting to the extension (and meeting the dimensional criteria);
  • The 6m (terraced/ semi-detached houses)/ 8m (detached houses) is measured from the original (or pre 1948) line of the house… if your house is staggered, then the 6m/8m line will stagger accordingly… it’s not simply 6m/8m from the furthest point of the house.
  • This will take 42 days to determine. Only two weeks less than Full Planning, but if you are certain that the neighbours are on side, you are certain of obtaining consent.

This legislation was designed to free up the planning process, where people would extend, say 3.6m to, perhaps to line through with an existing neighbour’s extension.

The assent of your neighbours is key… if your neighbour were to extend 6m/8m beyond your dining room window, would you be happy?

What if my neighbours object?

Under the standard PD criteria (3m/4m) your neighbours would not be consulted, although it is advisable that you engage with them once you know what you’re doing, as this will make the ongoing construction process more painless.

If your neighbours do object to a larger (prior notification) extension. You will need to go to full planning.

 Your neighbours objecting will not guarantee a refusal, although in the case of a 6m extension, this may well be the case.

The main drawback is that if enough neighbours object to Planning Application (the number varies from borough to borough) you will need to go to a Planning Committee.

Neighbour objection need not mean a planning refusal.

I need to apply for planning. What should I do?

Unsurprisingly, I think you should contact an Architect.

Good internal design, might reduce the level to which you need to extend. Conversely a well assembled application with a well-argued supporting statement will be more persuasive with the planners, should you really want to push the boat out.

Aside from the topic of Planning (and most importantly), you’ll only want to do this once, for this house at least. Best get it right!

Although only required in Conservation Areas, a Design and Access Statement helps to spell out less cut and dry cases. Additional information, such as sunlight studies may also reassure planners. At the very least it will make them consider the case more carefully as you do have the right to appeal a refusal. If your case is made strongly in the first instance, your chances are better at appeal and this may persuade the planners that this would better be avoided by granting consent in the first place, rather than facing the expense of a successful appeal.

Present a strong, well-argued case. Use a suitably qualified professional if necessary.

 How long will it take?

The council should deal with a domestic Planning Application in 8 weeks from the registered submitted date. Occasionally validation checks will delay this date, should there be an issue with the submitted information. This appears to happen more often when the planners are overloaded and less able to hit their 8-week deadline!

As Planners need to deal with a certain percentage of cases in the 8 weeks, they will normally deal with straightforward cases (a definite yes or no) first. If your case misses the 8 weeks, there’s less incentive for the planners to be timely.

It is advisable for you or your Architect to track the application, particularly after all the neighbourhood consultations have been received. You may be able to adjust the application during the 8-week period to respond to any concerns that the planners or your neighbours may have.

Going to committee extends the process. You need to wait for the next available committee (a nightmare through the summer holidays) in the hope that your scheme makes it onto the list.

Keep tracking your application and be prepared to negotiate.

What happens at a Planning Committee?

If enough people object (numbers vary from borough to borough), your case will be presented by planners to a select group of local councillors that make up the Planning Committee. The planners will make a recommendation (ideally for approval) and you or your representative (ordinarily the Architect) will present the case and answer questions. Objectors may also speak.

Even when planners recommend approval, Planning Committees can unfortunately be political affairs, especially around local elections. Perfectly reasonable schemes may be rejected if there is well connected or vocal opposition and vice versa. Of course, you have the right to lobby your local councillor, who may also speak on your behalf.

It’s also remarkable how voting is often along party lines, with disregard for the merit of the case as presented by the Planners. This is another reason for presenting your application professionally in order to raise the spectre of an appeal. It’s not great for councillors to refuse a scheme and have an independent Planning Inspector disagree later. This is a reasonable consideration for councillors and is often raised at committees.

If you need to go to committee, consider lobbying your councillor.

What if my application is refused?

A refusal will list specific reasons and policies, when issued. If you’ve been in dialogue with the planners you may know, before a refusal is issued, what policies will be used to justify the decision.

Assuming it is too late to adjust the scheme, you have three options.

  • The first is to withdraw the application, although you may not wish to prejudice the records of your site with a refusal. Even if you feel justified to appeal, the process is long and the odds are usually against you. A withdrawal, adjustment and resubmission is much quicker and less painful;
  • The second is get refused and resubmit. Contrary to the above paragraph, sometimes, having reasons for refusal recorded allows you to respond to those specific issues, as long as you know what will be listed and feel that you can work with those reasons. This approach means that there is less scope for the planners to devise other reasons to refuse the scheme. This is less likely to be the case for a domestic application, but my advice is to contact a professional (either an Architect or Planning Consultant);
  • Thirdly, get refused and appeal. This is a long term option and as such is not practical for most domestic projects. Appeals take anywhere between 6 months and a year to resolve. The stats are roughly 2:1 in the planners’ favour. If you feel that this is your favoured route. I would definitely consider using a Planning Consultant.

Planning refusal is not the end of the line although it might be time to engage a Planning Consultant to discuss your options.

I have planning consent. What next?

Building the scheme will be covered in another article, but the basics are that you have three years to commence the works, unless specifically contradicted by the consent.

Check your consent thoroughly, including drawing numbers and conditions. Check which conditions need to be discharged before you start on site. Failure to do so may invalidate your consent.

So long as all your pre-commencement conditions are discharged, if you carry out a material operation e.g. digging a trench, your consent is protected in perpetuity. Get the works recorded and ideally inspected by Building Control. You only need to do a small bit, then cover it up.

Secure your planning permission, by starting within the three year period, or you might need to reapply. Planning policy changes and Conservation Areas can extend.

Neel Dakshy is a RIBA Chartered Architect with over fifteen years' experience working with domestic clients in and around South East London, often in sensitive neighbourhoods, involving the skilled remodelling, conversion and extension of existing buildings for modern family life. Neel went to school in the area and returned after graduating from the University of Edinburgh. Having carried out extensive work to the family home in Hither Green, where he lives with wife Sarah (heavily pregnant during the project!) and three children, Neel empathises with those who are loathe to leave the community and wish to extend in order to stay. Neel sat on the Lewisham Design and Conservation Panel for seven years and is currently a parent governor at his children's primary school in Lee.