Before you come up with a plan to build an extension to your house, you should familiarise yourself with the rules and restrictions surrounding this. This article will walk you through some of these limitations and hopefully will be helpful during the planning process.
Permitted Development Rights Still Apply
Lots of small extensions fall under permitted development (PD) rights, which means that you don’t need planning permission beforehand. In 2025, there are some notable tweaks to PD rules to reflect environmental and urban planning goals.
Usually, under PD, rear single-storey extensions can extend up to 6m for terraced/semi-detached or 8m for detached homes. For two storey extensions, the limit is typically 3m. Additionally, the extension cannot cover over 50% of the land around the original property and it cannot be more than 4m in height on single-storey houses. Materials must also be “similar in appearance” to the original design. Flats, homes in conservation areas and Article 4 Direction areas are excluded from PD and don’t share the same rights.
New Energy Efficiency Standards
2025 has been met with stricter energy efficiency standards as part of the UK government’s effort to reach net zero by 2050. This relates to extensions as U-value limits are tighter, double glazing is a standard with triple glazing now being incorporated to projects and you should have proper ventilation with trickle vents on windows or other systems.
Must Comply with Building Regulations
Even if your extension is allowed under PD rights, you still must comply with all building regulations such as structural safety, fire safety, sound insulation, ventilation and thermal efficiency. Windows and doors are impacted here as you must have glazing in critical areas (like near stairs) and fire escape windows must meet new size and opening criteria.
Working with a reputable windows and doors supplier can ensure your chosen products are fully compliant and suitable for Building Control approval.
Planning Permission
Large or unusual extensions will usually require full planning permission through the council. In 2025, local councils have a focus on design consistency, flood risk and environmental performance. Consider using sustainable materials and submit clear architectural drawings for the best chance to get accepted.
Neighbours
The Neighbour Consultation Scheme still applies when planning larger single-storey extensions and involves notifying adjoining homeowners and giving them 21 days to raise any objections. Then, the council makes a decision after viewing all the parties’ information.
Contact Us – Help with Your Extension Today:
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