Ask an Architect: Do You Really Need Planning Permission For That?

Hugo Tugman

Monday, October 19, 2015

If your local planning department is proving difficult to deal with, it’s often possible to sidestep them using your Permitted Development
(or PD) rights. These rights give most houses automatic planning consent for a range of modest alterations, from rear extensions to loft
conversions, within a set of parameters. The rights still apply within conservation areas (although to a limited extent) and even to most
listed buildings.


Here’s a summary of the main points, although please only use this as a general guide, as the detail of what is and is not allowed can get fiendishly complex. Seek the advice of an architect who’s used to residential work; he or she will be able to give you specific advice and more detail.


Don’t forget other required permissions
In many instances, what is possible through Permitted Development would be refused if applied for under a planning application, so it can be about much more than just making the process simpler and quicker.

However, while PD can simplify the process, it’s important not to confuse the planning consent it can avoid with other necessary requirements, such as Building Regulations, party wall legislation and Listed Building Consent, to name a few, which permitted development will not replace. Always seek the advice of an expert before proceeding.


Build a simple rear extension
Probably the most common use of Permitted Development is for a single-storey, ground-floor extension to the rear of a house. On a detached house it can extend up to 4m back from the rear wall, and on a semi-detached or terraced house up to 3m – even in conservation areas. It can have a pitched or flat roof as long as the highest point is no more than 4m from the ground (which is pretty high) and the eaves (where the gutter is) is no more than 3m from ground level.

There are in fact quite a few pedantic limitations on what you can and can’t do under PD and it’s easy to inadvertently overstep the mark and find yourself in difficulties. Applying to your planning department for a Lawful Development Certificate (LDC) in advance gives you a rubber stamp to say that what you’re doing is within the limits. I always recommend seeking such a certificate before building anything and this will be an important document in the future if you want to sell.


Aiming high? Apply for planning permission instead…
It’s important to point out that if what you’re proposing is outside these limitations, it may be perfectly possible to build it anyway – it’s just that you’ll have to go through the process of a full planning application before knowing whether or not it will be allowed.

This extension, which I think looks fantastic, would have needed a full planning application as it’s too high from the ground to have been allowed through the PD process. However, in this instance I would say it was very much worth the extra time and trouble.


…but Permitted Development will let you go longer
The planning permission process has long been blamed for holding back growth in the building industry, and central government and local authorities have often fought legal battles over policy and control.

Planning permission policy is set by local authorities, while the Permitted Development rules are set by central government.

In the depths of the recession, as an attempt to stimulate the building industry, the government temporarily extended the legislation to double the 4m limit to 8m and the 3m limit to 6m. However, if going for the extra size, a ‘neighbour consultation process’ was introduced to try to protect neighbours’ amenities. Only once this is cleared can longer extensions be built under PD. The temporary legislation was due to run out in 2016, but it’s been very popular and has now been extended to 2019.


Consider two storeys
In some circumstances, rear extensions on two storeys are also permissible under PD. For two-storey extensions the limits are tighter – no more than 3m back from the rear wall and no part of the extension can be within 2m of a boundary (which rules out most small, terraced and semi-detached houses).

This part of the PD allowance is also ruled out for houses in conservation areas.

The maximum heights are clearly higher than for single storey extensions, but must be no higher than the eaves (gutter-line) of the original house.


Go for a bit on the side
Side extensions can also fall within the allowance of PD. An important rule to remember here is that they can extend sideways as far as half of the width of the original house again. Side extensions under PD can only be single storey and are ruled out completely for houses in conservation areas.

With all of the PD-allowed extensions mentioned so far, forget those old ‘volume calculations’, which have not applied since the rules all changed in 2008. Before then, all your permitted development extensions (to the side, roof, rear etc) could not exceed a sum total volume and many people still think that applies, but don’t worry, that rule has gone.


Get a lofty perspective
All the extensions I’ve mentioned thus far fall under the first part of the PD rules, called Class A, but that’s only one part of it. Class B deals with extensions to roofs. This most commonly means dormer extensions, which can provide more useable headspace and daylight in a loft conversion.

This house has both a single-storey, ground-floor extension (which would be allowed under Class A) and a little box dormer on the roof (which would have been allowed under Class B).

It’s possible to mix and match, too. For example, if you want to build a ground-floor extension that’s outside the limits of PD, but a loft dormer that’s within PD but might be refused under planning, you can apply for your extension under planning and separately build your loft under PD.


Max out your loft allowance
While the old volume calculations are long gone in Class A, as mentioned already, the one place they remain is with lofts under Class B.

As long as you stay no higher than the highest part of the roof, the rules allow you to build additional volume of up to 40 cu m on terraced houses and up to 50 cu m on semi-detached and detached houses. These allowances are pretty generous in all honesty and most small houses would struggle to get near to the maximum anyway, but you can often come up against the limit on larger houses.

This image shows one house, on the right, that has been extended with a fairly standard box dormer, probably well within the volume limit. The owners of the house on the left, however, have really gone for it, extending over the rear part of the house, too, getting an additional room and probably knocking close to the maximum.


Use both sides if you can
The one thing the rules will not allow is a dormer on the front pitch of your roof. But if your house (as many do) has a front gable and a roof that slopes down to gutters on each side, you are allowed under PD to build dormers on both sides.

Be careful that you retain the attractiveness of your house, especially from the front (I’ve seen this done horrendously badly in some cases), but with careful external design, you can create wonderful open space on your loft level this way.


Extend to the front
While the vast majority of Permitted Development relates to the rear and sides of houses, there’s a way of extending to the front – albeit only to a modest extent.

Class D of the rules allows for the construction of a porch. It does not restrict this to open porches, so effectively it allows a small front extension, as long as it’s around an existing doorway and is no more than 3 sq m in plan area or 3m high.


Build in the garden, too
Quite separately and additionally to anything you do to extend the house or loft, PD also gives rights under Class E to construct outbuildings.

Again, there are limitations: they cannot be forward of the front of the house; they cannot take up more than 50% of the garden space (although that would often be absurd anyway), and there are height restrictions.

However, as long as the use of the building is ‘incidental to the enjoyment of the dwelling house’, you can use it for pretty much anything you like. It can be fully heated, insulated, plumbed and wired, so could be an additional bedroom, home office or, as in this picture, a wonderful art studio.

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