Single Storey vs Double Storey Extension: Which Is Better for Surrey Homeowners?

If you are planning to extend your Surrey home, one of the first decisions is whether to go single storey or double storey. Both add significant space and value. But the cost, planning requirements, disruption, and what you get for your money are quite different.

This guide compares the two options honestly so you can make the right decision for your property, your family, and your budget.

At a Glance Comparison

	Single Storey Extension	Double Storey Extension
Typical cost in Surrey	£30,000 to £60,000	£55,000 to £110,000
Cost per m² added	£2,000 to £3,500	£1,500 to £2,500 (more efficient)
Planning permission	Often permitted development	Almost always required
Build time	8 to 14 weeks	14 to 24 weeks
Disruption	Moderate	Significant
Value added to Surrey home	10% to 15%	15% to 25%
Best use	Open plan living, kitchen extension	Extra bedroom plus living space
Garden loss	More (larger footprint)	Less (same footprint, more height)

Single Storey Extension: The Case For

Usually faster and less disruptive

A single storey rear extension typically takes eight to fourteen weeks to build. The work is contained at ground level and, in most cases, families can continue living in the house throughout the build. The main disruption is loss of access to the rear garden during construction.

Often permitted development

Single storey rear extensions up to 4 metres deep (for detached houses) or 3 metres deep (for semi-detached and terraced houses) generally fall within permitted development rights. This means no planning application, no eight-week wait, and no risk of refusal. Extensions under the prior approval neighbour consultation scheme can go up to 8 metres (detached) or 6 metres (semi-detached/terraced).

Creates transformational open plan living

The most popular use of a single storey extension in Surrey is creating a large open plan kitchen, dining, and living area at the back of the house. With bi-fold or sliding doors opening onto the garden and a roof lantern above, a well-designed single storey extension fundamentally changes how the ground floor feels and functions.

Lower overall cost

A single storey extension costs less in total than a double storey. If your primary goal is more ground floor living space rather than additional bedrooms, a single storey achieves exactly what you need for less money.

Double Storey Extension: The Case For

More space for less cost per square metre

A double storey extension adds floor area on two levels using the same footprint. The foundations, scaffolding, and structural frame are shared between both floors, which makes the cost per square metre significantly lower than building two separate single storey extensions.

If you need both a larger ground floor and additional bedrooms above, a double storey delivers both for considerably less than two separate projects would cost.

Stronger impact on property value

In Surrey, where bedroom count directly affects property value, adding a bedroom through a double storey extension typically has a stronger positive impact on resale value than an equivalent amount of additional ground floor space. A four-bedroom Surrey home commands significantly more than a three-bedroom home of similar square footage.

Less garden lost

A double storey extension uses the same garden footprint as a single storey but delivers twice the floor area. If your garden space is limited and you need significant additional floor area, going upwards is more efficient than going outwards.

Resolves multiple needs at once

Most Surrey families who choose a double storey extension are solving two problems simultaneously: they want more ground floor living space and they need an additional bedroom or bathroom above. A double storey addresses both in a single project with a single period of disruption.

Planning: The Key Difference

Planning permission is where the two options diverge most clearly.

Single storey: often no planning needed Most single storey rear extensions in Surrey proceed under permitted development, meaning no planning application is required. This saves time (typically 8 to 12 weeks), cost (£258 planning fee plus architect fees), and eliminates the risk of refusal.

Double storey extensions almost always require a full planning application. The process typically takes eight weeks for a decision, and there is always a risk of refusal or conditions being attached. In conservation areas or for listed buildings, the planning process for a two-storey extension is more complex and requires greater care in the design.

Grand Innovations handles the planning process for all extension projects and can advise on the likelihood of approval before any application is submitted.

Which Is Better for a Surrey Home?

The right choice depends on what you need:

Your Situation	Better Option
Want open plan living space and have enough bedrooms	Single storey
Need an extra bedroom as well as more ground floor space	Double storey
Limited budget, want maximum value for money	Single storey (lower total cost)
Want the best cost per square metre added	Double storey (more efficient)
Want to avoid planning permission if possible	Single storey
Have limited garden and need maximum space	Double storey
Prioritising fastest completion	Single storey
Planning to sell in next 3 to 5 years and want maximum value added	Double storey (more bedrooms)

Frequently Asked Questions

Is a double storey extension worth the extra cost in Surrey?

In most cases, yes. A double storey extension in Surrey adds more value per pound spent than a single storey because it increases the bedroom count. In Surrey’s property market, an additional bedroom has a strong positive impact on resale value. If you need both ground floor space and a bedroom, a double storey is more efficient than two separate projects.

Can I build a double storey extension without planning permission?

In most cases, no. Double storey rear extensions do not fall within standard permitted development rights. A planning application is required. Side extensions of two storeys always require planning permission. Grand Innovations handles the planning application as part of every double storey extension project.

How long does a double storey extension take to build?

A double storey extension in Surrey typically takes fourteen to twenty-four weeks of construction, following planning approval. Including the planning application period, the total time from starting the process to moving into the new space is usually six to nine months.

Which adds more value: single or double storey extension?

In Surrey, a double storey extension typically adds more total value because it increases the bedroom count as well as floor area. A single storey adds strong value through improved ground floor living space. The return on investment per pound spent is broadly similar for both, but the absolute value increase is usually higher for a double storey.

Can I extend single storey now and add a second storey later?

Sometimes, but it requires careful planning. If you want to build a second storey above a future single storey extension, the foundations and structure of the single storey must be designed to carry the additional load. Grand Innovations can design a single storey extension that is future-proofed for a second storey if this is part of your long-term plan.

Find Out What Is Right for Your Surrey Home

Grand Innovations has designed and built extensions across Surrey, from simple single storey kitchen extensions to complex double storey additions with full interior fit-out. We offer free consultations, clear proposals, and fixed-price contracts with no large deposits.

We cover Surrey, Epsom, Putney, and all surrounding areas.

Book your free consultation today and we will design the extension that works best for your home and your budget.