Upward Extension Rules
In the U.K., there are laws set out regarding extensions as with most construction. Every homeowner has what is known as ‘permitted development rights’.
However, these rules were introduced in 2020, and since then, the process of going ahead with constructing under these rights has not been very linear for many homeowners. There are still many complications that can arise as a result of these rights and ultimately, it is up to your local council as to how they deal with such cases. Often, a double-storey extension with prior approval as per the rights, can be refused.
There are limits to extending a property vertically and if you do not follow the rules set out, you are breaking the la, which as you can imagine, comes with serious repercussions.
With this said, there is a clause that you should be especially mindful of in the legislation that was made lawful in 2020, it states:
“You cannot extend a house without planning permission if it has been extended before, either by you or its previous owners. This rule covers extensions made since the 1st of July 1948.”.
This means that if you own an older, period property such as a house dating back to the Victorian era, you cannot extend the property upwards.
Properties constructed before July 1, 1948, or after October 28, 2018 (for home extensions) or March 5, 2018 (for new flats) cannot undergo extensions without planning permission, which excludes approximately 38% of homes.
While applying for planning permission remains an option, the seemingly easier route may not be accessible. Therefore, we always say that caution is advised, as inaccuracies in specifying construction dates (e.g., selecting “built between 1948 and 2018” for older houses) can lead to refusals and timely processing.
We strongly recommend that you only pursue prior approval for double-storey extensions if certain the house was built post-July 1948. You should also be made aware that it is up to you, the applicant, to provide proof of the dates a property was built. Therefore, you will need to be able to source historic maps, records, and title deeds to demonstrate that your building was constructed after 1948.
As part of this demonstration, you must prove that the entire structure was constructed after 1948. If part of the existing house was built before this time, you will also be denied approval.
What About Double-Storey Extensions in Conservation Areas?
Your property won’t be eligible if situated in a conservation area, an area of outstanding natural beauty, a site of special scientific interest, a national park, the Broads, or a World Heritage Site. Additionally, the new permitted development right (PDR) cannot be applied to listed buildings.
Permitted Development Rights for a Double-Storey Extension
The 2020 GDPO permits that:
Homeowners can expand their homes by two additional storeys. For those with terraced or semi-detached houses, one extra storey can be added with new flats. Owners of detached houses have the option to add two storeys, incorporating new flats above.
However, as we have mentioned already, the majority of councils in the U.K. will deal with prior approval applications in the same manner as full planning applications.
Councils generally refuse these extensions based on numerous factors including the height of extensions interfering with views and the need for preservation of the neighbourhood’s character.
What Limitations Are in Place for a Two-Storey Extension?
Whether you wish to carry out a two-storey rear extension or add a side extension onto a terraced house, you must follow the general rules set out:
- Every floor has a maximum internal height of 3 metres or the floor-to-ceiling height of the tallest existing floor, whichever is less.
- For a single-storey house, you can increase the height by a maximum of 3.5 metres; for a detached house with two or more stories, the increase can be up to 7 metres.
- The additional floors must not protrude beyond the front or side of the existing building, and no external support structures for the new floors should be visible.
- The pitch of the new roof must match that of the existing roof. This requirement is crucial, as it may prevent the use of a flat roof or mansard roof to maximise space while adhering to the height restrictions.
- Your property must not be located in a designated protected area, and its construction must have taken place between July 1948 and 2018.
Using Your Permitted Development Rights
After reading the guidance set out above, you should have a clearer idea of how you may be able to extend your home under permitted development rules.
The 2020 rules in place will allow you to extend your home to build flats. If you intend to rent out your home, this could be good news. With this said, not everyone benefits from this rule and prior approval is needed even to use these new permitted development rights in practice.
Other Considerations for Double-Storey Extension Designs
As our guide has covered, there are specific limitations for extending an existing house upwards, especially regarding height restrictions.
It is also important not to overlook how your two-storey extension will impact the privacy of your neighbourhood. In urban and suburban areas, councils place great emphasis on maintaining privacy and preventing the blockage of light due to construction.
There is also a need to consider the materials that you will use for a double-storey extension, as councils often prefer that similar materials to the original house are used. Each council provides its own guidelines for design, though an Architectural Designer can help you with this crucial part of the process.
The expertise of an Architectural Designer goes beyond just designing aesthetically pleasing structures; it encompasses navigating complex planning regulations, ensuring compliance with building codes, and creating a seamless integration of the new double extension with the existing house.
With our knowledge and experience, we can bring your design to life and maximise the functionality and appeal of your home. Contact us today to begin your extension project and make your design vision a reality.
