Planning a House Extension: Key Considerations Before You Start

Adding a house extension to your home can be a great way to create extra space and enhance everyday living.

However, extending a property involves more than just design decisions. Understanding the legal requirements, practical considerations, and planning your approach carefully can make a big difference to the success of your project.

1. Understand If Planning Permission Is Required

In Scotland, certain smaller extensions may be allowed under Permitted Development Rights, meaning full planning permission isn't always needed. However, strict rules apply, including:

• The extension must not cover more than half the area of the original house.

• It must not be higher than the original roof.

• Extensions within 1 metre of a boundary must have eaves no higher than 3 metres.

• Extensions to the front of a house often require full planning permission.

  
  

Regulations can vary depending on the property's location (for example, conservation areas). It's important to check directly with the local authority's planning department early in the process.

2. A Building Warrant Is Almost Always Needed

Even if planning permission isn’t required, a Building Warrant is likely necessary. In Scotland, a Building Warrant is required for most extensions and ensures compliance with the Building (Scotland) Regulations 2004, including standards for:

• Structural integrity

• Fire safety

• Energy efficiency

• Accessibility

Starting construction without a Building Warrant can result in enforcement action or difficulties in selling the property later.

3. Prioritise Good Design and Practical Layout

A well-designed extension doesn't just add space; it enhances how a home functions. When considering the design:

• Maximise natural light with glazing and rooflights where possible.

• Pay attention to insulation and heating efficiency to meet energy standards.

• Plan layouts that work with the existing structure and flow of the home.

• Avoid overshadowing neighbours or affecting their privacy.

Good early planning can avoid costly changes during construction.

4. Budget Realistically for All Costs

Many homeowners budget for construction but forget to include:

• Professional design fees (architectural or technical design)

• Planning and Building Warrant application fees

• Structural engineering reports or certificates (if required)

• Potential utility diversions (e.g., drainage)

Understanding the full cost from the outset can prevent delays and unexpected expenses.

5. Seek Early Professional Advice

Engaging with a qualified architectural designer or consultant early in the process can:

• Clarify whether permissions or consents are needed

• Identify any constraints on the site

• Help prepare a realistic budget and timeline

• Reduce risks of costly mistakes later

Local knowledge of planning policies, building standards, and site conditions is invaluable when extending a home.

By taking time to plan properly, understand regulations, and get expert advice early, a house extension project can be a rewarding and smooth experience. Careful preparation sets the foundation for a successful build that adds real value and usability to your home.