Planning Consultant - Chris Scott
Hi, I’m Chris,
I hold anĀ MA in Planning and work as a Planning Consultant

If your looking to extend your home or replace your dwelling you may have come across the term ‘original dwelling‘. But what does it actually mean and why is it so important when it comes to trying to secure planning permission? Let’s start with the planning definition of the original dwelling:

What does the term ‘Original Dwelling’ mean?

How the dwelling stood as of July 1st 1948. If contrusted after this date as it first stood.

Why is the Original Dwelling set on July 1st 1948?

On July 1st 1948 the Town and Country Planning Act 1947 came into force. This act of Parliament is the basis for modern planning in the UK and has been extended and amended several times over the decades. As this point in time is seen as the starting point for modern planning law, this date also set the point at which the size of a dwelling would be regarded as the ‘original’.

The Original Dwelling and National Planning Policy (NPPF)

In terms of national planning policy when the term original dwelling comes into play is with regards to properties within the Greenbelt. One of the main purposes of the Greenbelt is to ‘preserve openness’. Therefore, any development which reduces openness within the Greenbelt is seen to be inappropriate. However, there are exceptions to this rule, for instance, there are exceptions with regards to dwellings. Those rules are under section 145 of the NPPF, and are as follows:

(c) the extension or alteration of a building provided that it does not result in disproportionate additions over and above the size of the original building;

(d) the replacement of a building, provided the new building is in the same use and not materially larger than the one it replaces;

Therefore the determined size of the original dwelling when located in the greenbelt should be the starting point for any potential designs. One thing to note about the Greenbelt is that basements do not impact on openness. Therefore this could be a design consideration on a replacement dwelling to gain additional floorspace.

How Do You Prove The Size of the Original Dwelling?

So what sort of evidence can be used to demonstrate the size of the original dwelling, and what weight can be given to that evidence. First and foremost, it might be a good idea as part of pre-application planning advice from your local authority to ask them what evidence they have. They may provide evidence of an OS map which is not in the public domain. For instance, I’ll often use, but there is often gaps in the record.

Finding the Right OS Map as Evidence

So let’s presume we are looking into a building which is older than July 1st 1948. What date of OS map and type of map are we looking for? We really want to find a map as close to that date as possible, ideally just before July 1st 1948. The reason being any previous extensions before that date will be counted as the ‘original’. Furthermore, we need an OS map at a suitable scale. We want to be able to measure the floor area of the dwelling, therefore a 1:10,560 map is really no good to us. The scale of OS map you want to find is 1:2,500, that’s the scale of the most detailed OS maps available from around July 1st 1948.

Old Planning Applications as Evidence for the Size of the Original Dwelling

You may be able to search for old planning applications online through your local authorities website. Otherwise, as part of your pre-application discussions ask if there are any records of older applications which do not feature online. In there are you should be able to go down to the local council offices to view the applications. Unfortunately, if you ask them to send copies via email it is likely the council will charge you. Within these older applications there maybe floorplans which can be used as evidence for the original dwelling. Obviously, you want to find planning applications as close to July 1st 1948 as possible. If the plans are a few years after 1948 it may be possible to ‘reasonably’ argue the size of the original dwelling.

Local Planning Policies Based on the Size of the Original Dwelling

Under national planning policy, there is local planning policy. This will be covered under a document called either the Local Plan or the Core Strategy. Within this document, there may be policies specifically about extending or replacing dwellings in open countryside or the Greenbelt. For instance, there may be planning policy restrictions based on a percentage of the original dwelling. It’s quite common to see a limit of up to 30% allowed over the size of the original dwelling. However, each area and each local plan is different.

Permitted Development Rights are a ‘Material Consideration’

Once appropriate evidence of the size of the original dwelling as been sourced, there may be a problem. Your proposals may be significantly more than the size of the original dwelling. However, there may still be a way to secure approval for the proposals. It involves accurately demonstrating the full permitted development rights of the property. If this can be done successfully then these permitted development right will be considered a ‘material consideration’ in a planning decision. Commonly referred to as the ‘fall back position’ of the applicant.

If your proposals under planning permission are approved, then its highly likely the permitted development rights for the property will be removed. Using permitted development rights to illustrate what ‘could’ lawfully be done to a property can be a powerful tool. Even more so now that it appears the Larger Homes Extension will become a permanent right.

Conclusions on the Size of the Original Dwelling

It’s worth spending some time or getting a planning consultant such as myself to look into the size of your original dwelling. You then need to consider existing extensions. Only then should you spend time on designing your proposals. You should also note that a detached garage is unlikely to be regarded as part of the ‘dwelling’. Demonstrating permitted development rights effectively could also be the difference between approval and refusal of a planning application.