All You Need to Know About Building Extension Planning Permission Rules

All You Need to Know About Building Extension Planning Permission Rules

Building an extension, whether a smaller one-storey rear extension that isn’t visible from the front of your home to a major two-storey wrap-around extension or loft conversion that transforms the roof line of your property, can add significant value, and transform the space and accommodation within your home.

Planning permission is often misunderstood, where homeowners assume that the planning permission process is complex, costly, and difficult, and they forgo their dream designs or extension plans solely to ensure the extension work falls under permitted development rights.

However, the best way forward is to clarify where you will need formal written consent from the local authority, analyse the potential costs of that approval, and ensure you work with an experienced, reputable and talented extension team to ensure the result is everything you have aspired to.

How Does Planning Permission Work With Home Extensions

In most cases, planning consent is a mandatory requirement if the extension you wish to build will make a substantial change to the outward appearance of your property, such as the proximity to a rear boundary, the degree to which your home overlooks your neighbours or the appetence of the structure from the road.

That said, we often speak with homeowners who assume planning permission is extremely costly and will almost always mean they cannot proceed with their perfect extension, which isn’t the case. Provided you have comprehensive technical plans and designs and can fully comply with local council planning rules, even the most impressive extension can obtain official permission.

As a brief and general overview:

    • Larger extensions require consent, but you can reduce the requirements or likelihood of being turned down by using energy-efficient, sustainable, and locally sourced materials that match the current exterior of your home.
    • If your extension is large, but you’re keeping the new roofline lower or consistent with your current roof height, you may be less likely to need consent.
    • Where permitted development applies, and you don’t need consent, you might also need to consider Party Wall agreements and building regulations – meaning that falling within permitted development doesn’t necessarily mean you won’t need alternative approvals or agreements to proceed.

Planning applications for extensions usually fall under the ‘householder planning permission‘ category rather than needing full planning permission. Most homeowners pay a total charge of £328. If there are no contentions or challenges, then aside from the cost of the initial planning and technical designs, you won’t need to budget a significant amount to gain approval.

Which Home Extensions Require Formal Planning Consent?

While planning permission is often much more streamlined and less disruptive than our clients anticipate, we also recognise that many would prefer to stick within the permitted development rules and forgo any need to apply for official permission to proceed with their planned extension.

Below, we’ve summarised the most popular forms of extension and the limitations within which you can build without consent. It’s important to clarify that caveats apply, and the standard planning rules aren’t always consistent in specific areas.

For example, if your home falls into one of the below categories, you may require consent for any planned extension works, even if the project is relatively minor or won’t make any significant difference to the external aesthetic of your property:

    • Properties within UNESCO World Heritage Sures
    • Homes located inside the boundaries of National Parks
    • Buildings in Areas of Outstanding Natural Beauty
    • Houses within conservation areas or with Grade I or II listed status.

If any of these conditions apply, we recommend speaking with the local authority responsible for granting building work within certain limits or reviewing how the rules apply to a listed building.

What Extension Projects Are Included in Permitted Development Rights?

Permitted development means that, as a homeowner, you can complete work, improvements, or extension builds on your property without requiring any form of official permission or consent from the local council.

However, it’s also worth reiterating that planning permission isn’t the only potential regulation you’ll need to consider. Planning consent is required where modifications to a property could potentially impact the way the building affects the local environment, whether the appearance of an area or how other properties are overlooked or affected by construction close to a boundary.

Building regulations are separate and mandatory rules that ensure any work completed in your home, whether or not it is considered an approved development or falls under permitted development rights, is safe, constructed to industry standards, and complies with health and safety regulations.

Therefore, any house extension, small or large, should be completed by experienced contractors who can self-certify that their work adheres to building regulation standards or provide the necessary documentation to certify that your extension is fully compliant.

How Can I Build a Single-Storey Extension Without Planning Permission?

Single-story extensions can be planned up to a height of four metres and within four metres of the back wall of the existing property without needing planning consent. Excluding conservatories, the materials you use in your build should match the appearance of your existing house without extending toward a main road via the front or side of your home.

Which Double Storey Extensions Require Planning Consent?

Larger extensions that reach up to the first floor of your home will not usually require planning consent, provided that:

    • The extension doesn’t read three metres beyond the current rear wall of your home.
    • The roof pitch matches the property as it is or is very close to the current design and height.
    • Your new extension will not have a roof life that hits three metres or more.
    • The extension will be built with materials that appear close to the aesthetic of the original property.
    • There are at least seven metres between the rear boundary of your home and the end of the extension.
    • Any side elevations with a window are obscure glazed and do not open.

Importantly, any elevated platforms, like a balcony, veranda, or other structure, may require planning permission—even if the broader scope and design of your extension are allowed under permitted development.

As we’ve seen, most planning permission rules linked to extensions relate to the height of the build, the proximity to the boundary, and the distance between the new roof line and any existing edge of your property.

That said, planning permission isn’t always particularly involved or complex, and an experienced contractor can provide support in the form of technical drawings and construction plans that meet all of the local authority’s requirements to grant full consent.

If you’d like more information about building extension planning permission, permitted development, and building regulations, you are very welcome to contact the experts at Pinnacle Works for more tailored guidance.