How Much Does a Home Extension Cost in Harlow? | 2026 Local Guide
With house prices continuing to rise and demand for larger family homes remaining strong, many homeowners in Harlow are choosing to extend their properties rather than move. A well-planned home extension can provide valuable extra space, improve layout and significantly increase property value — but understanding the costs involved is essential before starting.
This guide explains how much a home extension costs in Harlow, what factors affect pricing, the different types of extensions available, and how to budget realistically for your project in 2025.
Average Home Extension Costs in Harlow
Extension costs vary depending on size, complexity and finish. As a general guide, typical extension costs in Harlow include:
- Single-storey extension: £1,800 – £2,500 per m²
- Double-storey extension: £2,000 – £2,800 per m²
- Rear extension: £30,000 – £60,000+
- Side extension: £35,000 – £70,000+
- Wrap-around extension: £55,000 – £100,000+
These figures provide a useful starting point, but final costs depend on several key factors specific to your property and plans.
What Affects the Cost of a Home Extension in Harlow?
1. Size and Layout
Larger extensions naturally cost more, but layout also plays a role. Simple open-plan layouts are often more cost-effective than designs with multiple rooms, bathrooms or complex structural changes.
2. Type of Extension
Different extension types come with different cost implications:
- Single-storey extensions – Usually the most affordable option
- Double-storey extensions – Higher upfront cost but better value per square metre
- Wrap-around extensions – Offer maximum transformation but at a higher price
3. Ground Conditions and Foundations
Groundworks can significantly affect costs, particularly if:
- Deeper foundations are required
- Drainage needs relocating
- Ground conditions are poor
A site assessment helps identify these issues early.
4. Structural Alterations
Many extensions involve:
- Removing internal walls
- Installing steel beams (RSJs)
- Altering roof structures
Structural work adds complexity and cost but is often essential for creating modern, open-plan living spaces.
5. Specification and Finishes
Internal finishes can have a major impact on the final price, including:
- Flooring and tiling
- Kitchen units and appliances
- Bathroom fittings
- Windows, doors and glazing
Choosing mid-range finishes can help balance quality and budget.
Do You Need Planning Permission for an Extension in Harlow?
Many home extensions fall under Permitted Development, meaning planning permission may not be required if size and design limits are met.
Planning permission is more likely to be required for:
- Double-storey extensions
- Extensions close to boundaries
- Side or front extensions
- Properties in conservation areas or Old Harlow
Regardless of planning permission, Building Regulations approval is always required.
Single-Storey vs Double-Storey Extensions: Cost Comparison
Single-Storey Extensions
- Lower overall cost
- Shorter build time
- Ideal for kitchen and living spaces
Best suited to homeowners who want to improve layout without adding bedrooms.
Double-Storey Extensions
- Higher upfront cost
- Better value per square metre
- Adds bedrooms and bathrooms
Often the better choice for growing families or long-term living.
How Long Does a Home Extension Take?
Typical build times include:
- Single-storey extension: 8–12 weeks
- Double-storey extension: 12–20 weeks
Timescales depend on design complexity, weather conditions and material availability.
How Much Value Can an Extension Add in Harlow?
A well-designed extension can add 15–25% to a property’s value, especially when it:
- Improves layout and flow
- Adds bedrooms or bathrooms
- Creates open-plan living space
In family-friendly areas of Harlow, extensions are often seen as a strong long-term investment.
Budgeting Tips for Your Extension Project
To keep your project on track:
- Define your requirements early
- Allow a 10–15% contingency
- Prioritise structure and layout over finishes
- Request detailed, itemised quotes
- Work with an experienced local builder
Clear planning reduces unexpected costs.
Why Use a Local Harlow Builder for Your Extension
A local builder offers:
- Knowledge of Harlow housing styles
- Familiarity with local planning expectations
- Reliable site management
- Access to trusted local suppliers
Local builder experience helps ensure your extension is delivered efficiently and to a high standard.
Final Thoughts
Understanding home extension costs in Harlow is a vital first step before starting any building project. While prices vary depending on size and specification, careful planning and professional advice can help you achieve the best results within your budget.
Whether you’re extending for extra space, modern living or long-term value, a well-planned home extension remains one of the most effective ways to improve your property in 2025.