How Much Does a House Extension Cost in Ipswich? A Local Builder’s Guide
A house extension is one of the most effective ways to gain the space your family needs without leaving the home and location you’ve chosen. In Ipswich, where property prices have risen steadily and the costs of moving — stamp duty, estate agent fees, solicitor costs, and the upheaval itself — easily run into tens of thousands, extending your existing home often makes more financial sense than buying something bigger. You invest the money directly into usable space and property value rather than handing a significant chunk to agents, lawyers, and the taxman.
But house extension costs vary considerably depending on what you’re building, how large it is, what specification you choose, and what your specific property requires. This guide sets out realistic prices for different types of extension across Ipswich, explains what drives the cost at each stage, and helps you set a budget that reflects what your project will actually involve.
Single Storey Extension Costs
A single storey rear extension is the most popular project we build across Ipswich. It adds ground floor space — a larger kitchen-diner, an expanded living area, a home office, or a ground floor bedroom — without the cost and complexity of building upward.
A modest rear extension of around three metres deep across the width of a standard semi-detached house typically costs between £22,000 and £34,000. This covers foundations, brickwork, a flat or lean-to roof, standard patio or bi-fold doors, plastering, electrics, basic plumbing if needed, flooring, and decoration. The extension is finished and habitable but the specification is practical rather than premium. Many of the semi-detached properties across Whitton, Castle Hill, and Chantry suit this size of extension well.
A larger extension of four to six metres deep with a higher specification — quality aluminium bi-fold doors, skylights or a roof lantern, underfloor heating, and a fully fitted kitchen within the new space — typically costs between £35,000 and £55,000. The additional depth means bigger foundations, more brickwork, a larger roof structure, and substantially more internal finishing. This is the most common bracket for Ipswich homeowners creating open-plan kitchen-diners that transform the ground floor.
A premium single storey extension with the highest specification — large-format sliding doors, structural glazing, a flat roof with a central lantern, stone or porcelain flooring, underfloor heating throughout, a high-end kitchen installation, and comprehensive finishing — can reach £55,000 to £75,000 or more. The larger detached properties in Kesgrave, Rushmere St Andrew, and the villages around Woodbridge typically commission extensions at this level.
Double Storey Extension Costs
When you need space on both floors, a double storey extension delivers the best value per square metre. Building two storeys shares foundations, walls, and roof structure across both levels, costing significantly less than constructing the same total area as separate single storey projects.
A double storey rear extension in Ipswich typically costs between £35,000 and £68,000 depending on the size and specification. The ground floor usually provides an enlarged kitchen-diner or living space while the first floor adds one or two bedrooms, a bathroom, or an ensuite above.
The cost per square metre tells the value story clearly. A single storey extension typically works out at £1,700 to £2,400 per square metre. A double storey comes in at £1,300 to £1,900 per square metre because the expensive elements — foundations, groundwork, scaffolding, and much of the external brickwork — only happen once regardless of how many storeys sit above them.
However, double storey extensions almost always require planning permission from Ipswich Borough Council, adding eight to twelve weeks for the application process and introducing uncertainty about the outcome. The design needs careful consideration of impact on neighbours, overlooking, and light to adjacent properties. These planning requirements make the double storey route slower to start but the financial advantage in cost per square metre often justifies the additional time.
Side Return and Wrap-Around Extensions
Many of Ipswich’s Victorian and Edwardian terraces — particularly those around the Waterfront, through the town centre streets, and into Stoke Park — have narrow side passages running alongside the property that serve no practical purpose beyond storing bins. Extending into this strip adds valuable width to the ground floor without taking significant garden space.
A side return extension on its own typically costs between £15,000 and £28,000 depending on the length of the return and the specification. The structural work involves removing the side wall, installing steelwork, and building a new external wall along the boundary.
Combining a side return with a rear extension creates a wrap-around — an L-shaped addition that maximises the ground floor footprint. Wrap-around extensions typically cost between £30,000 and £55,000 and deliver the most dramatic ground floor transformations, often doubling the usable kitchen and living space in one project.
What Affects the Cost?
Several factors push the price above or below the typical ranges, and understanding them helps you anticipate where your project sits.
Size is the most straightforward variable. Extension costs work roughly on a per-square-metre basis, with the rate typically decreasing slightly on larger projects because certain fixed costs don’t scale proportionally. A three metre extension costs less than a five metre extension, but the five metre extension costs less per square metre because scaffolding, skip hire, building control fees, and site setup happen once regardless of size.
Ground conditions matter more than most homeowners expect. Ipswich sits on a mixture of clay, sand, and gravel depending on exactly where in the town your property sits. Properties near the river and Waterfront area may encounter higher water tables. Properties on the clay soils across the western estates may need deeper foundations where trees are close to the build. Your builder should assess the ground conditions during the initial site visit and account for them in the quote. Standard strip foundations suit most Ipswich sites, but some require trenchfill or engineered solutions that add cost.
The rear opening has a significant impact on both cost and how the finished room feels daily. Standard patio doors cost between £800 and £1,500. Quality aluminium bi-fold doors spanning three to four metres typically cost £3,000 to £6,000. Large-format sliding doors can reach £5,000 to £8,000. The price difference is substantial, but so is the difference in daily experience — wide-opening doors that connect the kitchen with the garden transform how the room functions compared to a modest patio door.
Roof design affects both cost and character. A flat roof with a membrane finish is the most common and affordable option for single storey extensions. Adding a roof lantern or skylights brings natural light into the centre of deeper extensions where it’s furthest from the windows — making a meaningful difference in rooms that would otherwise feel dark in the middle. A pitched roof matching the existing house costs more but creates a more traditional appearance.
Internal specification covers everything from the kitchen fitting and flooring to the heating system and decoration quality. A basic plaster finish with painted walls and laminate flooring is practical and affordable. Underfloor heating, engineered wood or porcelain flooring, and a fully fitted kitchen with stone worktops transform the specification and the cost. Being clear about your priorities before requesting quotes ensures the prices you receive reflect what you actually want.
Planning Permission in Ipswich
Single storey rear extensions benefit from generous permitted development allowances. For attached houses 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 or eight metres for detached are possible through the prior approval process.
Double storey extensions, side extensions visible from the highway, and any work that exceeds the permitted development conditions require a full planning application through Ipswich Borough Council. Applications typically take eight to twelve weeks for a decision. The town centre and parts of the older streets have conservation area designations that add further planning sensitivity — particularly around the Waterfront and Christchurch Park where the character of the streetscape is protected.
Your builder should assess the planning position for your specific property at the outset and advise clearly before any design work progresses.
Getting the Best Value
Get itemised quotes from two or three experienced builders. Compare like for like — check that each quote covers the same specification, the same scope, and the same finishing standard. Without consistent scope, comparing prices is meaningless because you’re not comparing the same job.
Invest in the elements that matter longest. Quality foundations protect everything above them for decades. Properly installed steelwork supports the structure permanently. Quality doors and windows affect how the room looks, feels, and performs thermally every single day. A well-fitted kitchen shows immediately and lasts for years. These are the elements where quality pays for itself over time.
Where you can economise without lasting compromise is decoration and fixtures that are straightforward to upgrade later. Paint, light fittings, and door furniture are all easy to change in a few years. Foundations, structural steel, and a properly constructed roof are not.
Build in a contingency of ten to fifteen percent above the quoted price. Ground conditions, drainage complications, and structural discoveries when the existing wall is opened are normal in extension work. A contingency means they’re absorbed within the budget rather than becoming a problem that forces difficult decisions mid-build.
Getting Started
If you’re considering an extension at your Ipswich home, get in touch for a free consultation. We’ll visit your property, discuss your requirements, assess the site and the planning position, and provide a detailed, itemised quote so you can plan your project with confidence before committing to anything.