Planning permission is one of the most intimidating facets of a building project and something we’re often asked about. It is a complex area but there are ways to navigate it to ensure you are building with appropriate permission and have set realistic budgets.


What are the rules for planning permission and permitted development?

Planning permission is subject to your local authority’s approval, and the first challenge is that each authority has a different set of parameters that they are working to. So if you have moved from one area or county to another, don’t assume that planning permission parameters that applied on a previous building project are the same for your new property.

Permitted development is very broad in its definition and may not even apply if you live in an Area of Outstanding Natural Beauty (AONB). These areas are very protected from development and have their own rules. If you’re planning to buy a property or plot in an AONB, it is crucial that you look into the permitted development and planning rules if you are hoping to extend, build or change of use. Location is key to permitted development parameters, so never make assumptions about what you can or cannot do in these types of protected areas.

We have completed a number of projects in the Ashdown Forest which is an AONB but planning permission must be sought and this can be a lengthy and involved process. The best approach is to be forewarned and forearmed so embark on the process expecting to have your plans scrutinised and changed in order to meet regulations and approval.

In general terms (but we can’t stress enough that you need to check with your own local authority!) under permitted development rules you should be able to:

  • Replace a like for like structure
  • Extend by 30sqm with a max of 4m height

These parameters often apply to structures such as a replacement garage or new garden room for a home office or gym.


Will a new extension require planning permission?

If you are bolting something onto your house, this is considered to be an extension. Whether it falls under permitted development or needs planning permission is very much down to your location, your existing building and the materials you’re planning to use. For example, if your new extension features a lot of glazing, you are more likely to need planning permission, even if it is less than the permitted development of 30sqm. This is due to the impact on your energy rating. Using a lot of glass is likely to lower your energy rating so Building Control will want to have a more in-depth understanding of the project and how the energy rating will be managed.

If you can keep existing external doors and windows, technically this can prevent your energy rating from being downgraded so is an aspect of your design that is worth looking into.

It is important to note that loft conversions will always require planning permission, especially if you are having a dormer included. Don’t assume because it is an internal project, it must fall under permitted development!


Will a garden room need planning permission?

As mentioned previously, garden rooms often fall under permitted development so are can be a great solution for adding a home office, gym, guest room or teenager den to your home without the costs or planning associated with an extension. Check the permitted development parameters in your area and be aware of how your structure could impact your neighbours. If the new garden room could impede or block a neighbour’s natural light or views, you may need to build it in a different location than originally planned.


Residential Vs Agricultural planning permission

Rules for farm outbuildings differ from the rules we need to abide by for residential builds. Farm buildings can usually be much bigger and subject to a more relaxed approach to planning. This is especially true if the building is not enclosed, i.e. a large open hay barn is much easier to get planning for than a secure warehouse of the same dimensions.

Thankfully, change of use planning development has been relaxed and simplified so derelict agricultural barns and stables can often be developed into residential dwellings. However, the foundations tend to be very different in agricultural buildings and will normally need to be modified or replaced to meet modern Building Control standards. This groundwork will be costly so make sure you have explored these costs and the work involved when planning your timeline and budget.  This is something we can advise you on too, so don’t hesitate to get in touch to discuss your development project with us.


Check for Tree Preservation Orders

This is so easy to overlook but so important to check. If you have any very established mature trees on your property that you plan to remove, make sure there are no protection orders you need to be aware of. Tree preservation orders are common but the good news is that it is easy to find out if your trees have them. A simple phone call to the council should be all you need to do to find out and is well worth doing.

If you do have an issue, sometimes the council will accept the removal of mature trees if you can replant on your property once the build is completed. This is worth discussing in a pre-planning consultation with your local planning office.


Listed buildings

If you’re looking to extend or undergo a change of use for a listed building, it is really worth engaging an architect who specialises in listed properties. There are so many elements to navigate and to give you the best chance of getting your planning application approved, you really need to engage the services of an experienced architect specialising in this field.

One of the challenges we regularly face when working on listed buildings is marrying modern techniques and materials with the bones of the older building. Often you have to do a hybrid approach where you adopt some historic methods alongside your more modern techniques that deliver the right aesthetic but also ensure Building Control sign off. This is something we are very experienced in accomplishing and can guide you on.


Pre-planning consultations

Often the central decision in extending a listed property is whether the new addition is going to be in keeping with the original building or a modern contrast. Before you get too far along with your architect designs, we recommend you book an appointment with a planning officer. This will be so valuable in ascertaining what your local planning department is open to, and what you need to take into account to give you the best chance of approval when you finally submit the application.

It is likely that you will need to pay for a consultation but it is well worth the investment to get this insight straight from the planning department. If you book the consultation early enough in your process, it could save you from extensive re-design fees and enable you to plan your budget and timeline much more realistically.  This knowledge upfront is really useful in terms of material choice too. For example, if the existing building has a traditional lime mortar, the planning office may expect you to use the same mortar on the new extension. This type of mortar was commonly used on very old properties but is not easily available now and would have to be formulated in a lab to exactly match the original mortar. Elements like this can really impact your budget.

Take the time at the outset of the project to unearth these potential costs and challenges by having a pre-planning consultation and it will really help you put together a realistic budget and plan with your project team.

It is always helpful to have some basic drawings and photos to refer to in your consultation too, you want to make it as clear as possible for the officer to see what you’re trying to achieve.


Ready to get the ball rolling and plan an extension or change of use project? We have lots of experience helping clients navigate through the planning system and working alongside Building Control. Talk to us about your project at or call on 01825 740 482.