Objective

This guide walks London homeowners through planning a two storey side extension, from early design choices and approvals to costs and the stages that follow.

 

Key Takeaways

• A side extension adds rooms upstairs and downstairs while leaving most of your garden untouched.
• Most double-storey projects need council approval, so check planning permission early.
• Costs depend on size, foundations, structure and finishes, so ask for an estimate once a concept exists.
• Simple roof shapes and standard materials can keep spending under control.
   

Introduction

Are your kids outgrowing their rooms while the house you love feels a little smaller every year?

Moving can mean a new school, a new commute and a lot of stress. A double storey side extension lets you stay put and add bedrooms, a bigger kitchen or a proper home office by widening the house instead of using up the garden.

Many London homeowners like the idea but don’t know how to get started. Compared with a single-storey addition, two storey extension brings more structure, more paperwork and more decisions.

Let’s walk through what you should know before you call anyone.

 

What Does Double Storey Side Extension Planning Involve?

A well-run two storey side extension starts with questions, not blueprints. Here’s how the early stages usually unfold at Studio 20 Architects.

• A free initial site consultation lets an architect hear what you need, such as another bedroom or a bigger kitchen.
• The process also includes a site survey and a feasibility study, so you learn what your property can realistically hold.
• Concept design then brings detailed drawings that let you visualize the layout before construction begins.
• Design options arrive with expert support and advice, so you can compare choices before you commit.
• The same team can stay involved through tender, contract administration and site supervision.

 

Do You Need Side Extension Planning Permission?

Most double-storey extensions need the council’s approval, particularly when they affect neighbors or go past certain limits. If you’re set on a double-storey side extension, it’s wise to check the rules before paying for detailed plans.

• In a conservation area, even small changes to the outside of a home may need approval.
• An Article 4 Direction removes some permitted development rights, so even smaller changes then need an application.
• Pre-application advice lets you ask the council what they are likely to accept before you apply.
• Most councils take about eight weeks to decide a standard application, and larger projects can take longer.
• On its South Croydon project, the team followed the council’s rules on maximum height, distance from neighboring properties and local character.

 

What Shapes the Double Storey Extension Cost?

Although no single price fits every home, a side extension often costs more than a single-storey one because it needs more structural support, new roof connections and sometimes party wall agreements.

• The size of the side projection and the overall footprint form the base of your budget.
• Site access and foundations count as well, and structural work or drainage can add noticeably to the total.
• Window choices, finish quality and any demolition work all move the price.
• Your engineer’s structural calculations show what the walls, beams and foundations must safely carry.
• Smart choices such as simple roof forms, standard materials and less complex structure can lower the total without hurting quality.

Ask for an estimate once you have an initial concept, because that’s when size, materials and structure can be measured properly.

 

How Should You Approach Double Storey Extension Design?

A double storey side extension works best when the new rooms feel like they’ve always belonged. One Studio 20 project in South Croydon, a double-storey side and rear extension, shows what that can look like.

• The finished home features five bedrooms, five bathrooms, two offices and an open-plan kitchen, dining and living space.
• Bay windows let plenty of natural light into the living areas and add a sense of depth, which helps rooms feel larger.
• Floor-to-ceiling windows and sliding doors brighten the open-plan kitchen and dining area and connect the home to the outdoors.
• Render and timber cladding, clean lines and a neutral color palette gave the outside a modern look.

 

What Happens From First Visit to Finished Home?

Studio 20 Architects follows six stages, and knowing them ahead of time makes the whole project feel far less overwhelming.

Stage	What Happens
Initial consultation	A free site consultation helps the team understand your needs.
Concept and planning design	Drawings reflect your ideas, and we prepare and submit the planning application for you.
Technical design	Once approval arrives, detailed building regulations drawings are prepared for construction.
Tender pack	Materials and finishes are specified.
Contractor selection	Final packs go to proven principal contractors in the studio’s network.
Contract administration	The building contract is run through to practical completion.

Moreover, approval from Building Control normally stays valid for three years, so it’s worth starting work within that window.

 

Ready to Give Your Family the Room It Needs?

The best double storey side extension fits your home, your council’s rules and the way your family lives. When design, approvals, technical details and budget are considered together, moving forward feels far more manageable.

If you’re weighing up a property extension in Wandsworth, Richmond, Kingston or nearby, Studio 20 Architects offers a free consultation where you can share your ideas and receive a transparent quote. Request a quote or call 0203 432 2770 to get started.

Frequently Asked Questions

Is there a standard double-storey extension cost per Square Meter?

A per square meter benchmark is a handy place to start budgeting, but location and specification move the final figure. An architect or estimator needs your details before they can give you a firmer number.

Can My Neighbors Stop My Extension?

Neighbors can comment on your application, yet the council makes the final decision using planning rules rather than personal opinions. Considering how the extension affects nearby homes early in the design can help.

How Long Does a Double-Storey Extension Take?

Timelines for a double storey extension London project usually run 4 to 6 months from design to finish, covering planning and construction. Size, complexity and permissions can move that either way.

Can a Double-Storey Extension Add Value to My Home?

Yes, it can raise your property’s market value significantly, while also adding space and improving how the home works and looks. A free consultation is the easiest way to see what’s realistic for your home.