Single Storey vs Double Storey Extensions: Which Is Right for Your Ipswich Home?
When you’ve decided to extend your Ipswich home, the first major question is whether to build one storey or two. The answer seems like it should be straightforward — if you need space downstairs, build a single storey extension, and if you need space upstairs as well, build a double storey. But the decision involves more than just how many rooms you want to add. Cost, planning requirements, construction time, disruption, impact on neighbours, and the proportions of your existing property all play into which option makes the most sense for your specific situation.
This guide compares single and double storey extensions from a practical standpoint, covering the real costs, the planning differences, and the factors that Ipswich homeowners should consider before committing to either approach.
What Does Each Option Give You?
A single storey extension adds ground floor space only. The most common use is a rear extension creating a larger kitchen-diner, an expanded living area, a home office, or a ground floor bedroom and wet room. The extension sits under its own roof at the back or side of the house, typically with a flat roof or a lean-to pitch that meets the existing wall below the first floor windows.
A double storey extension adds space on both the ground floor and the first floor. The ground floor typically provides the same enlarged kitchen-diner or living space, while the first floor adds one or two bedrooms, a bathroom, or an ensuite above. The extension shares a continuous roof structure with the existing house, creating a more substantial addition that significantly increases the overall size of the property.
The difference in usable space is significant. A three metre deep rear extension across the full width of a typical Ipswich semi gives you roughly twelve to fifteen square metres of additional ground floor space. Build the same extension as a double storey and you gain that same ground floor space plus an equivalent area above — twenty-four to thirty square metres total from the same footprint.
Cost Comparison
Cost is usually the deciding factor, and this is where double storey extensions offer a compelling advantage. Building two storeys does not cost twice as much as building one, because the most expensive elements — foundations, groundwork, and the roof — serve both floors.
A single storey rear extension in Ipswich typically costs between £22,000 and £45,000 depending on the size, specification, and amount of finishing work included. A modest three metre extension at the lower end, a generous full-width extension with bi-fold doors and a high-specification kitchen-diner at the upper end.
A double storey rear extension of the same footprint typically costs between £35,000 and £70,000. The additional cost covers the first floor walls, the first floor structure, the extended roof, the internal fitting of the upstairs rooms including plastering, electrics, plumbing for any bathrooms, flooring, and decoration — but the foundations, groundwork, scaffolding, and much of the external brickwork only need doing once.
The cost per square metre tells the story most clearly. A single storey extension in Ipswich typically works out at £1,800 to £2,500 per square metre. A double storey extension comes in at £1,400 to £2,000 per square metre because the fixed costs are spread across a larger area. If you need space on both floors, a double storey extension delivers significantly more room per pound spent than building separate single storey projects.
That said, if you only need ground floor space, a single storey extension is the more cost-effective choice. Paying for a first floor you don’t need simply because the per-square-metre rate is lower doesn’t make financial sense. The right extension is the one that gives you the space you actually require at a price that works for your budget.
Planning Permission
The planning requirements differ significantly between single and double storey extensions, and this is where single storey projects have a clear advantage.
Single storey rear extensions benefit from generous permitted development allowances. For attached houses — the terraces and semis that make up much of Ipswich’s housing stock across areas like Rushmere St Andrew, Chantry, and Whitton — you can typically extend three metres from the original rear wall without planning permission. For detached properties, the allowance increases to four metres. Larger extensions up to six metres for attached houses or eight metres for detached are possible through the prior approval process, which is simpler and faster than a full planning application.
Double storey extensions are more restricted under permitted development. The maximum depth is three metres from the original rear wall, the extension must sit at least seven metres from the rear boundary, and the roof pitch must match the existing house. The eaves and ridge cannot exceed the height of the existing roof. If your property can’t meet these conditions — and many Ipswich homes with shorter gardens or close rear boundaries can’t — you’ll need a full planning application.
Planning applications add both time and cost. An application to Ipswich Borough Council currently takes eight to twelve weeks for a decision. Architectural drawings need preparing, the application fee needs paying, and there’s always a degree of uncertainty about the outcome until the decision is made. Planning officers consider the impact on neighbours, overlooking, loss of light, and the design’s compatibility with the existing streetscape.
For many Ipswich homeowners, the ability to build a single storey extension under permitted development — avoiding the planning process entirely — is a significant advantage in terms of both timeline and certainty.
Construction Time
Single storey extensions are faster to build. A typical single storey rear extension takes eight to twelve weeks from breaking ground to completion. A double storey extension takes twelve to sixteen weeks because there’s more structural work, more brickwork, more internal fitting, and an additional floor of plastering, electrics, plumbing, and finishing to complete.
If planning permission is needed for the double storey option, add eight to twelve weeks for the application process on top of the build time. A single storey extension proceeding under permitted development can start as soon as the design is finalised and building control is notified, putting you in your new space potentially months earlier than the double storey alternative.
Disruption
Both types of extension cause disruption, but the nature and duration differ.
A single storey extension concentrates the disruption on the ground floor. The rear wall is opened up, the kitchen or living room is out of action during the connection phase, and there’s noise and mess while construction is underway. But the bedrooms and bathrooms upstairs remain unaffected, and the disruption is shorter because the build is faster.
A double storey extension affects both floors. The ground floor disruption is similar, but upstairs you’ll also have construction noise, potential access issues while scaffolding is in place, and a period where first floor rooms adjacent to the new build may be affected by dust and vibration. The connection between the new first floor rooms and the existing landing involves structural work that temporarily impacts the upstairs circulation. Living in the house during a double storey extension is perfectly manageable but requires more patience and flexibility than a single storey build.
Impact on Your Property
The visual impact of each option on your home’s appearance is worth considering, particularly for the front elevation and the streetscape.
A single storey rear extension is largely invisible from the front of the house. The roofline doesn’t change, the front elevation stays the same, and neighbours and passers-by may not even realise you’ve extended. This makes single storey extensions straightforward in terms of planning acceptability and neighbourhood relations.
A double storey extension changes the roofline and the proportions of the property when viewed from the rear and potentially the side. A well-designed double storey extension that matches the existing roof pitch, materials, and proportions looks like it was always part of the house. A poorly designed one looks obviously bolted on and can dominate the original property. Good architectural design is more critical with a double storey extension than a single storey one, and it’s worth investing in proper drawings to get the proportions right.
For properties in Ipswich’s older streets — the Victorian terraces around Spring Road, the Edwardian housing in Christchurch Park area, and the period properties through the town centre — a double storey extension needs particularly careful design to complement the existing character. Planning officers will scrutinise the design closely in these locations, and rightly so.
Which Suits Your Ipswich Home?
The right choice depends on what you actually need and what your property can accommodate.
Choose a single storey extension if you primarily need more ground floor space, your garden is deep enough to extend meaningfully, you want to avoid the planning application process, your budget is tighter, or you want the project completed as quickly as possible. Single storey extensions are the right answer for the majority of Ipswich homeowners looking for a bigger kitchen-diner, more living space, or a ground floor home office.
Choose a double storey extension if you need space on both floors, the cost per square metre matters because you’re adding significant area, your garden and boundary distances allow double storey development within permitted development or you’re comfortable with the planning process, and you want to maximise the value added to your property. A double storey extension suits growing families across Ipswich who need both a larger kitchen-diner and additional bedrooms or bathrooms.
Consider a single storey extension now with a future double storey in mind if your budget doesn’t stretch to both floors today. Building the single storey with foundations designed to support a future first floor addition means you can add the upper storey later without starting from scratch. This phased approach costs slightly more overall than building both storeys at once, but it spreads the investment and gives you the ground floor space you need immediately.
Getting Started
Whichever option suits your situation, the starting point is the same — a conversation about what you need, an assessment of what your property can accommodate, and honest advice on the best approach for your specific circumstances.
If you’re considering an extension at your Ipswich home, get in touch for a free consultation. We’ll visit, discuss your requirements, and provide a clear, detailed quote so you can make an informed decision about your project.