Timeline: How Long Does an Extension Take in Farnham?

One of the most common questions we get from homeowners in Farnham is “How long will my extension actually take?”

The honest answer is: it depends on size, complexity, and approvals — but most single-storey home extensions in Farnham typically take 12–20 weeks of construction time once work starts on site.

Below is a realistic timeline based on typical domestic extensions and refurbishments we deliver across Farnham and the surrounding Surrey and Hampshire areas.

🏡 Stage 1 — Design, Planning & Pre-Construction

Typical timeframe: 6 – 16 weeks

This stage often takes longer than the build itself and includes:

• Architectural design

• Planning permission (if required)

• Structural engineer calculations

• Building control approvals

• Detailed cost planning

• Party wall agreements (if needed)

💡 In Farnham, planning can be quicker for permitted development extensions, but conservation areas and listed buildings can add time.

🚜 Stage 2 — Groundworks & Foundations

Typical timeframe: 2 – 4 weeks

Includes:

• Site setup

• Demolition (if required)

• Excavation

• Concrete foundation pour

• Drainage works

• Substructure brick/block work

Ground conditions in parts of Farnham can vary, which sometimes affects excavation depth and programme.

🧱 Stage 3 — Superstructure & Roof

Typical timeframe: 3 – 6 weeks

Includes:

• External walls and structure

• Steel installation (if required)

• Floor structures

• Roof construction

• Roof covering (tiles / flat roof / leadwork)

At this point, the extension becomes weatherproof.

⚡ Stage 4 — First Fix Services & Internal Build

Typical timeframe: 3 – 5 weeks

Includes:

• First fix electrics

• First fix plumbing and heating

• Internal stud walls

• Insulation

• Plaster boarding

🎨 Stage 5 — Plastering, Second Fix & Finishes

Typical timeframe: 3 – 5 weeks

Includes:

• Plastering

• Second fix electrics

• Second fix plumbing

• Joinery and carpentry

• Decorating

• Flooring

🌿 Stage 6 — External Works & Completion

Typical timeframe: 1 – 3 weeks

Includes:

• Patios / landscaping

• Drainage completion

• External making good

• Final building control sign-off

⏱ Typical Total Build Time (On Site)

Extension Type	Typical Build Time
Single storey extension	12 – 16 weeks
Side return extension	10 – 14 weeks
Double storey extension	16 – 24+ weeks
Extension + full refurbishment	20 – 32+ weeks

📍 What Can Affect Extension Timelines in Farnham?

• Planning conditions

• Structural complexity

• Steelwork design

• Ground conditions

• Weather (especially winter groundwork)

• Client design changes mid-build

• Bespoke materials or glazing lead times

🤝 How We Keep Projects On Programme

At Forsyth Construction Surrey Ltd, we focus on:

• Detailed pre-construction planning

• Clear weekly scheduling

• Trade coordination

• Realistic programme setting from day one

This reduces delays and helps clients plan around the build with confidence.

If you’re considering an extension in Farnham and want realistic timescales based on your specific property and design, we’re always happy to provide early guidance.

If you’re planning an extension in Farnham and want clear, realistic advice on programme, cost and buildability, our team is here to help. Every project is different, and early guidance can save significant time and cost later in the process.

Contact us today to discuss your plans, and we’ll talk you through realistic timelines, key considerations and next steps to move your project forward with confidence.

Frequently Asked Questions – Extension Timelines in Farnham

How long does planning permission take for an extension in Farnham?

Most planning applications are decided within 8 weeks, however this can vary depending on application complexity and local authority workload. If your extension falls under permitted development, you may not need full planning permission, but we always recommend confirming this before starting design work.

How long does a typical home extension build take in Farnham?

Most single storey extensions take around 12–16 weeks on site once construction begins. Larger, more complex or double storey extensions can take 16–24+ weeks, particularly if structural alterations or full refurbishments are included.

Can I live in my house during an extension build?

In many cases, yes — particularly with rear or side extensions. However, if the project involves major structural alterations, kitchen relocation, or full refurbishments, some clients choose temporary accommodation during key stages.

What usually causes delays to extension projects?

The most common causes of delays include:

• Design changes during construction

• Material or glazing lead times

• Structural design changes

• Unforeseen ground conditions

• Severe weather during groundwork stages

Good pre-construction planning reduces most of these risks.

When is the best time of year to start an extension?

Extensions can be built year-round, but starting groundwork in spring or early summer can reduce weather-related risks. That said, with proper planning and protection measures, winter builds are still very achievable.

Do extensions in Farnham need building regulations approval?

Yes — almost all extensions require building regulations approval, even if planning permission is not required. This ensures the structure, insulation, drainage, electrics and structural elements meet current standards.

How early should I speak to a builder before starting an extension?

Ideally, speak to a builder before or during design stage. Early input helps ensure the design is buildable, cost realistic, and programmed efficiently — saving time and money later.

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How much does an extension cost in Farnham?

Costs vary depending on size, specification and structural complexity, but early cost planning alongside timeline planning helps avoid surprises and keeps projects running smoothly.