Double Storey House Extensions
Need more living space but don’t want to move? A double-storey extension gives you twice the room without doubling your costs, perfect for expanding your home while adding long-term value and comfort.
Book your free double storey extension consultation with KNR Group today.
Maximises space and value
Two floors of new living area at a lower cost per square metre than single storey builds.
Adds long-term property value
Increases home value by 20–30%.
Future-proofs your home
Extra bedrooms, bathrooms or office space designed for growing families.
What is a Double Storey House Extension
A double-storey extension extends your home both upwards and outwards, creating two new levels of living space. It’s an ideal solution for families needing more bedrooms, bathrooms, or open-plan ground floor areas without relocating.
Whether you own a detached house in Essex, a semi-detached in London, or a traditional home in Hertfordshire, a double-storey extension provides flexibility to reimagine how your home works for modern living with added functionality and design appeal.
Why Choose KNR Group for Double Storey Extensions
KNR Group delivers high-quality, bespoke extensions designed to enhance your lifestyle and property’s potential. With decades of construction experience across London, Essex and Hertfordshire, we’re trusted by homeowners who value quality, transparency, and excellent service.
- Experienced architects and tradespeople for every stage
- Project-managed builds with clear communication
- Full planning, design and construction under one roof
- Proven results with minimal disruption
Contact KNR Group today for a free consultation and quotation.
Types of House Extensions
Our Process
Consultation and Site Survey
We assess your property, discuss your goals, and outline potential layouts.
Architectural Design
Tailored designs that meet your space, budget, and style preferences.
Planning and Building Control
KNR Group manages all permissions, drawings and compliance paperwork.
Construction
Managed by qualified professionals, ensuring precision, safety, and efficiency.
Completion
Every project is signed off with final inspections, certification, and warranties, ready for occupancy or sale.
Timelines and Build Duration
A double-storey extension typically takes 14–20 weeks from groundwork to completion, depending on complexity and weather conditions. Planning permission and design stages can take an additional 6–8 weeks, which KNR Group fully manages to ensure no delays.
Cost of a Double Storey Extension
The cost of a double-storey extension varies depending on design, materials, and finishes. On average:
| Extension Type | Typical Cost (Estimate) |
| Rear Double Storey | £80,000 – £120,000 |
| Side or Wraparound | £90,000 – £150,000+ |
Factors influencing cost include:
- Roof design and structural requirements
- Finishing quality (standard or premium)
- Plumbing and electrical work
- Access and site preparation
KNR Group provides detailed, transparent quotes so you know exactly what your project involves — no hidden costs.
Planning Permission for Double Storey Extensions
Double-storey extensions usually require planning permission, especially if they significantly change the building’s exterior.
KNR Group handles all aspects of planning, including:
- Preparation of architectural drawings
- Submission to local planning authorities
- Communication with building control
- Compliance with conservation or listed building requirements
Many extensions also need to follow local guidelines on height, proximity to boundaries, and design aesthetics, areas we specialise in navigating smoothly.
FAQs – Double Storey House Extensions
How much does a double storey extension cost in Essex?
A double-storey extension in Essex typically costs between £80,000 and £130,000, depending on size, structure, and finish. KNR Group provides tailored quotations for transparency and accuracy.
Do I need planning permission for a double storey extension in Essex?
Yes, most double storey extensions in Essex require planning permission, particularly if they alter the building’s height or layout. KNR Group handles all planning and compliance on your behalf.
How long does it take to build a double storey extension?
The average build takes around 14–20 weeks, with additional time for planning and design approvals.
Can a double storey extension add value to my home?
Yes. Professionally built double-storey extensions can add up to 30% to your home’s market value, making them one of the best long-term investments.
What’s the difference between a single and double storey extension?
A single storey adds ground-floor space only, while a double storey adds two levels, ideal for adding both living and sleeping areas for growing families.
Why Choose KNR Group for Your Double Storey Extension
- Experience and Precision – 30+ years of construction expertise across London and Essex.
- Design and Build Specialists – Complete project management under one roof.
- Trusted Locally – We’ve completed countless home extensions in Essex, London, and Hertfordshire.
Let’s discuss your project — request your free home survey today.
We'd love to hear from you and discuss your project
House Extensions & Renovation Projects
Client testimonials
Video Testimonial
This rear extension showcases KNR Group’s ability to deliver a smooth, well-managed build from start to finish. With clear communication and quality craftsmanship throughout, the result is a bright, open space that’s transformed how the homeowner lives day to day.