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House extensions in Dublin from €40,000, usually without planning permission up to 45 m² at the rear and 12 to 16 weeks on site.
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Build Me builds house extensions across Dublin, most often a bright single-storey kitchen-diner across the back. Two-storey, side return, wrap-around or glazed, we take it from the planning check and the engineer to the roof, the kitchen and the paperwork for your records.
Prices are build costs in Dublin at standard finish, including VAT at 13.5%. Professional fees, a 15% contingency and a new kitchen are extra.
€2,700 to €3,400 per m²
The extension most Dublin families build: a kitchen-diner or family room across the back of the house, opening onto the garden. Up to 45 m² at the rear it is usually exempt from planning. A 20 m² extension at standard finish costs about €54,000 to €69,000.
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€2,800 to €3,500 per m²
Built into the side passage to widen a galley kitchen or add a utility and downstairs toilet. A side return behind the rear wall can be exempt, but an extension to the side of the house needs planning permission. About €56,000 to €70,000 for 20 m².
€2,200 to €3,100 per m²
A bigger kitchen downstairs and a bedroom or bathroom upstairs, with one set of foundations and one roof, so it costs less per m². Two floors of about 20 m² each come to €88,000 to €138,000, and most need planning permission.
€3,100 to €4,000 per m²
Rear and side in one build, for the largest open-plan ground floor. Because part of it sits to the side, it usually needs planning permission. About €93,000 to €120,000 for 30 m².
€3,400 to €4,500+ per m²
A sunroom, orangery or glass box: a glass roof, glazed gable or wide sliding doors for as much daylight as possible. It is the dearest per m², and the price climbs with the amount of structural glazing, from about €68,000 for 20 m². Solar-control glass stops it overheating in summer.
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We're fully insured for your peace of mind, protecting your property throughout every stage of the work.
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Each phase of your project is led by dedicated specialists who excel in their specific area of expertise.
Pick the type of extension and its floor area. Under 40 m², fixed costs can push the price above the per m² rate, and the full calculator allows for that.
Extension type
Floor area
Estimated cost, incl. VAT
€54,000 to €68,000
Single-storey rear extension of about 20 m² in Dublin, standard finish, build cost before fees and contingency.
01
Every extension starts with new strip or raft foundations, drainage diverted around the footprint and a slab laid to meet the level of the house. In older Dublin houses, especially pre-1960s terraces and semis, the existing footings are often shallow, so an engineer checks them before the price is fixed.
02
Knocking through to the new room means steel beams (RSJs) to carry the walls above. Each one costs about €800 to €2,500 depending on span, and most open-plan kitchen extensions need two to four. Our structural engineer sizes every beam and signs it off.
03
A flat roof keeps a low, clean line and, under the exemption, must sit no higher than the eaves or parapet. A pitched roof can match the house but must stay below its highest point. Rooflights and roof lanterns bring daylight into a deep kitchen, and a glass rooflight adds more to the price than a solid roof.
04
Walls, floor and roof are insulated to Part L of the building regulations, so the new room is as warm as a new build. Large areas of glazing have to be balanced by better insulation elsewhere, which we plan at design stage rather than on site.
05
Radiators or underfloor heating, new lighting and sockets by a registered electrician, then plastering, flooring and decorating. A new kitchen in a kitchen extension adds €15,000 to €40,000, and a new bathroom about €7,000 to €13,000 in Dublin.
06
Exempt from planning does not mean exempt from the building regulations. We keep an engineer's certificate of compliance, product certificates and photos of the build-up before it is covered, because a buyer's solicitor will ask for them when you sell.
Most Dublin projects add 20 to 30 m² across the back of a semi, well inside the 45 m² exemption. A first floor over it is exempt only up to 12 m², smaller than most bedrooms, so a two-storey plan usually goes for planning permission.
A side return fills the narrow passage beside the rear return to turn a galley kitchen into a wide kitchen-diner. Materials and skips often have to come through the house, which is one reason terraced builds sit higher in the price range.
More space around the house means a side or wrap-around extension is possible, though both usually need planning permission. Upstairs, the exemption allows a first floor of up to 20 m² instead of 12 m².
Since 27 July 2026, a rear extension of up to 45 m² is exempted development under Class 1 of the Planning Regulations, as long as it meets the garden, height and boundary rules.
Usually exemptUp to 45 m² in total, with 25 m² of garden left.
Check firstFirst floor capped at 12 m² (semi-D) or 20 m² (detached).
Needs permissionClass 1 covers the rear only; a porch up to 2 m² is the exception.
It is a total, not a fresh allowance: every extension built since 1 October 1964 counts, including a converted garage.
Example: a 15 m² kitchen added in the 1990s plus a new 25 m² rear extension uses 40 of the 45 m². You must also keep 25 m² of garden.
They apply in full even when planning permission does not.
Going up costs less per m², because the foundations and roof are shared, but it usually means a planning application.
Cost per m² in Dublin
Build costs at standard finish, including VAT, from our extension cost calculator. Fees and contingency are extra. For other ways to add space, see attic conversions and garage conversions.
From the first visit to the handover, a single-storey extension takes about 12 to 16 weeks on site.
We look at the house, the garden, the drains and any earlier extensions, and talk through how you want to use the space.
Drawings, an engineer's input and a written quote. If the plan needs permission, add about 12 to 16 weeks here for the planning process.
Groundworks, foundations and slab, blockwork, steel beams, the roof, then windows and doors so the extension is weathertight.
Knocking through, first-fix electrics and plumbing, insulation, plastering, flooring, the kitchen and decorating.
Snagging, a final clean, a walkthrough with you and the compliance documents for your records.
Most of the extensions we build are single-storey rear kitchen extensions on Dublin semi-detached and terraced houses. We're fully insured, every job carries our 1-year workmanship warranty, and a typical single-storey extension takes 12 to 16 weeks on site.
Whatsapp chatSee how we extend Dublin homes with kitchen-diners, side returns and second storeys built to match the house they join.
Build Me recently completed a full renovation of our home. The whole process was handled professionally from start to finish. Communication was top-notch, with everything coordinated through a whatsapp group. Really happy with the final result.
Vasilij and team did an outstanding job with our recent house renovations. Their work was exceptional including flooring, tiling, painting plumbing/bathroom installation and other works. The team was always so pleasant, hardworking, diligent and professional.
I couldn't be happier with the fantastic job done by Vasilij, Michael, and Daniel! From start to finish, their professionalism, attention to detail, and craftsmanship were absolutely top-notch.
They expertly plastered and painted the walls with a flawless finish that completely refreshed the space.
Max and VJ did an amazing job in our kitchen. I had a timeline to finish the job within a week and they managed it very well.
Still have questions about your house extension? Call 01 270 9764 and we'll be happy to help.
A single-storey rear extension in Dublin costs about €2,700 to €3,400 per m² at standard finish, including VAT, so a typical 20 m² kitchen extension comes to about €54,000 to €69,000. Small extensions carry fixed costs for foundations, steel and the roof, so even the smallest starts from about €40,000. A two-storey extension costs less per m², about €2,200 to €3,100. Professional fees (about 10 to 12% of the build), a 15% contingency and a new kitchen (€15,000 to €40,000) are on top. Try the extension cost calculator for your own size and finish, or read our house extension cost guide.
Usually not for a single-storey rear extension. Since 27 July 2026, a rear extension of up to 45 m² is exempted development, as long as you keep at least 25 m² of private garden, the walls are no higher than the rear wall of the house and a flat roof sits no higher than the eaves or parapet. Front and side extensions need permission, apart from a porch of up to 2 m². Protected structures, Architectural Conservation Areas and some estates lose the exemption. See our guide to planning permission for extensions.
Yes. The 45 m² limit counts every extension built since 1 October 1964, including ones a previous owner added and ones that had full planning permission. A converted attached garage counts too. If a 20 m² kitchen was added in the 1990s, you have 25 m² left. If you are not sure, a Section 5 declaration from your council costs €80 and confirms whether your plan is exempt.
Sometimes. The first floor must be no more than 12 m² on a terraced or semi-detached house, or 20 m² on a detached house, at least 2 m from the boundary, with upstairs windows at least 8 m from the boundary they face. The total still has to stay within 45 m². Most bedrooms over a kitchen are bigger than 12 m², so most two-storey extensions on Dublin semis need planning permission.
A single-storey extension takes about 12 to 16 weeks on site, and a two-storey extension about 16 to 20 weeks. Design and drawings come first. If you need planning permission, allow about 12 to 16 weeks for the planning process, from drawings and notices to the final grant, before building starts.
Per square metre, usually yes. The foundations and the roof are shared across two floors, so in Dublin a two-storey rear extension costs about €2,200 to €3,100 per m², against €2,700 to €3,400 for a single-storey rear extension. The total is higher and it usually needs planning permission, but it adds a bedroom or bathroom upstairs as well as a bigger kitchen downstairs.
Check every quote for professional fees (architect, engineer and BER assessor), planning drawings if permission is needed (about €1,500 to €4,000), development levies in Dublin (about €20 to €30 per m² where they apply), extra steel beams (€800 to €2,500 each), a new kitchen or bathroom, and a 15% contingency for what only shows up once walls and floors are opened.
Yes, and bungalows are often the easiest houses to extend. A single-storey rear extension is exempt up to 45 m² in total, but its walls can be no higher than the bungalow's own rear wall, which keeps the roof low. Many bungalow owners combine a rear extension with an attic conversion: a side or rear dormer of up to 30 m³ is now exempt too, which can add bedrooms upstairs without planning permission.
Usually. A bigger kitchen-diner, an extra bedroom or a downstairs shower room is what most Dublin buyers pay more for, and a well-built extension makes a house easier to sell. How much it adds depends on your road and on what similar houses sell for, so ask a local estate agent before you set your budget, and keep the engineer's sign-off and compliance documents for when you sell.
Not for planning, if the extension is exempt. But any work on or over a shared party wall needs your neighbour's consent under the Land and Conveyancing Law Reform Act 2009, and the upper floor of an exempt extension must be at least 2 m from the party boundary. Talk to your neighbours early: it avoids disputes once the diggers arrive, and we can explain the plans to them with you.
Yes, in full. Since 27 July 2026 you no longer need a commencement notice for an exempt extension of up to 45 m², but the structure, fire safety, ventilation and Part L energy rules still apply. Keep an engineer's certificate of compliance, because a buyer's solicitor will ask for it when you sell. An extension that needs planning permission still needs a commencement notice.
