Planning Permission for House Extensions in Milton Keynes: What You Actually Need to Know
- Clarkson Construction
- 4 days ago
- 5 min read
Planning permission is one of the most misunderstood parts of extending a home. Many homeowners assume permission is always required, while others believe everything falls under permitted development - and both assumptions regularly lead to delays, redesigns, or enforcement issues.
If you’re planning a house extension in Milton Keynes or the surrounding Buckinghamshire area, understanding when planning permission is required - and when it isn’t - is essential before construction begins.
This guide explains how planning permission works in practice, what local authorities look for, and how to avoid common mistakes that slow projects down.
Do You Always Need Planning Permission for a House Extension?
No - but many extensions still do.
In the UK, some extensions fall under permitted development rights, meaning formal planning permission isn’t required. However, these rights are subject to strict rules around size, height, location and design. If an extension exceeds those limits, or the property has restrictions in place, planning permission will be needed.
In Milton Keynes, planning departments pay particular attention to scale, neighbour impact, street scene and compliance with local development frameworks. What works on one street may be refused on another. This is why many homeowners choose to confirm requirements early, rather than risk costly redesigns later.
If you’re still working through the early stages, our guide to architect drawings for house extensions explains how design decisions affect what can and can’t be approved.
When Planning Permission Is Required
Planning permission is usually required if your extension:
Extends significantly beyond the original footprint of the house
Is a double-storey extension that affects neighbouring properties
Alters the appearance of the front elevation
Is built on designated or restricted land
Involves a listed building or property with removed development rights
Even where permitted development may apply, interpretation varies. This is why many homeowners opt to secure a Lawful Development Certificate for certainty before construction starts.
Permitted Development vs Planning Permission: The Key Difference
Permitted development allows certain works to proceed without a full planning application, but it does not remove the need for compliance with building regulations. This is where many projects go wrong.
Even if an extension doesn’t require planning permission, it must still meet current structural, thermal, fire safety and drainage standards. This is covered through building regulations approval, which is a completely separate process.
If you’re unsure how this works in practice, our guide to planning drawings vs building regulations drawings explains the difference in detail and why both stages matter.
How Local Planning Works in Milton Keynes
Milton Keynes Council assesses applications based on:
Scale and massing of the extension
Impact on neighbours (light, privacy, outlook)
Design consistency with the existing property
Compliance with local planning policies
Extensions that are well-designed, proportionate and supported by clear drawings are far more likely to be approved.
This is why early collaboration between designers, builders and planning consultants is so important - especially for larger or more complex extensions.
Planning an extension and unsure where you stand? Speaking to an experienced builder early can help identify potential planning issues before drawings are finalised.
Common Planning Mistakes That Delay Extensions
Many delays happen before construction even begins. The most common issues include:
Submitting incomplete or unclear drawings
Designing beyond permitted development limits without realising
Failing to consider neighbouring properties
Assuming approval is guaranteed
Starting work before permission is confirmed
These mistakes often lead to redesigns, re-applications, or stop-work notices - all of which increase cost and stress.
How Builders Support the Planning Process
While builders don’t submit planning applications themselves, experienced construction teams play an important role in ensuring designs are practical, compliant and buildable.
At Clarkson Construction, we regularly work alongside architects and designers to review plans before construction begins. This helps identify potential planning or compliance issues early - saving time once work starts on site.
If you’re still in the early stages of planning, it’s worth speaking with your builder before finalising drawings, particularly for house extensions in Milton Keynes where site constraints can vary.
Learn more about why homeowners choose Clarkson Construction for complex extension and renovation projects.
Planning Is the First Step - Not the Only One
Securing planning permission (or confirming permitted development) is only one part of the process. Before construction can legally begin, building regulations approval must also be in place. This ensures the extension is safe, structurally sound and energy efficient - and is inspected during construction.
We cover this in detail in our next guide on whether you need Building Control for a house extension, which is essential reading before any build starts.
Frequently Asked Questions
What is the full process from drawings to construction in the UK?
The process typically starts with planning drawings, followed by planning permission (where required), then building regulations drawings. Once approvals are in place, construction can begin, with Building Control inspections carried out at key stages to ensure compliance.
Do I need both planning drawings and building regulation drawings?
In most cases, yes. Planning drawings focus on layout, appearance and impact, while building regulations drawings ensure the design meets UK construction, safety and energy standards. One does not replace the other.
Can you start building before building regulations approval?
Work should not begin until Building Control approval is in place. Starting construction without approval can lead to delays, redesigns or enforcement issues later in the project.
Who submits drawings to Building Control in Milton Keynes?
Drawings are usually submitted by your architect, designer or structural engineer, but builders work closely with them to ensure the construction matches approved details and passes inspections.
How long does it take to move from drawings to construction?
Timescales vary depending on planning requirements, drawing complexity and approvals. Once drawings are finalised and approvals granted, construction can usually begin shortly after, subject to scheduling.
What happens if drawings change during the build?
Minor changes can often be handled with revised details, but structural or regulatory changes may need updated drawings and approval from Building Control before work continues.
Do builders follow the drawings exactly?
Yes. Construction should follow approved drawings and specifications. Any deviation must be assessed to ensure it still meets planning conditions and building regulations.
Is Building Control required for all residential projects?
Most extensions, renovations and new builds require Building Control approval. Even permitted development projects must comply with building regulations.
Thinking About Extending Your Home?
If you’re planning an extension and want to understand the process properly before committing, it’s worth speaking with a construction team that understands both planning and build requirements. You can also explore our house extension services to see how projects are delivered from initial groundwork through to final handover.
Ready to discuss your extension plans? Whether you’re still at the planning stage or preparing to build, our team is happy to offer practical guidance based on real project experience.
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