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Rear, side and wrap-around single-storey extensions in Dublin from €40,000, about 12 to 16 weeks on site, with a rear extension up to 45 m² usually exempt from planning.
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Build Me builds single-storey extensions across Dublin, from a kitchen-diner across the back of a semi to a side extension or a wrap-around on a bungalow. Flat roof or pitched, with rooflights or a lantern, we handle the planning check, the engineer, the build and the handover.
Build costs in Dublin at standard finish, including VAT at 13.5%. Fees, a 15% contingency and a new kitchen are extra.
Across the back of the house, opening the old kitchen and dining room into one bright room on the garden. It is the one most often built without planning permission, up to 45 m² in total. A 20 m² single-storey rear extension in Dublin costs about €54,000 to €69,000.
€2,700 to €3,400 per m²
Built on the side passage or driveway to add a utility, a downstairs toilet, a playroom or a home office. Side extension ideas often start with a narrow strip, so the layout matters more than the size. A side extension needs planning permission, so allow for that in the timeline.
€2,800 to €3,500 per m²
An L-shape along the back and side in one build, for the widest open-plan kitchen, dining and living space. The corner usually needs a longer steel and more glazing, which is why it costs more per m². Because part of it is at the side, it needs planning permission.
€3,100 to €4,000 per m²
Mostly glass: a glazed roof, glazed walls or a glass box off the kitchen. It brings in the most daylight and costs the most per m², from about €68,000 for 20 m². We still build the base, walls and any solid sections in block, so it sits on proper foundations.
€3,400 to €4,500+ per m²
A bungalow is the easiest house to extend at ground level, because there is no first floor to support. The walls can rise no higher than the bungalow's own rear wall, so a flat roof with a lantern is the usual way to get height and light. It can turn a dated bungalow into a modern single-storey home.
€2,700 to €3,400 per m²
Pick the type and the floor area. Small extensions carry fixed costs, so one of up to 15 m² still comes to about €40,000 to €58,000. The full calculator allows for that.
Extension type
Floor area
Estimated cost, incl. VAT
€67,500 to €85,000
Single-storey rear extension of about 25 m² in Dublin, standard finish, build cost before fees and contingency.
01
We dig the footings, move any drain that runs under the new room and pour a slab at the same level as your kitchen floor, so there is no step between old and new. Shallow footings on older Dublin houses are checked by our engineer before the price is fixed.
02
Build Me builds single-storey extensions in traditional concrete block, insulated in the cavity and finished in render or brick to match the house. Block is solid, quiet and suits the Irish weather, and it is the only way we build.
03
Opening the rear wall into the new room needs steel beams sized by the engineer, at about €800 to €2,500 each. We prop the house, fit the steel and only then take the wall down, so the rooms upstairs never move.
04
Most single-storey extensions in Dublin have a flat roof, kept below the first-floor windowsills behind a neat parapet or fascia. A pitched or lean-to roof suits a cottage or a bungalow and gives a vaulted ceiling inside. Either way, the roof is insulated to Part L.
05
A deep kitchen extension needs light from above as well as from the garden. Flat rooflights are neat and cheaper; a roof lantern adds height and a real wow over an island. Wide sliding doors or bi-folds open the room onto the patio.
06
Underfloor heating or radiators, new lighting and sockets by a registered electrician, plaster, flooring and paint. A new kitchen adds €15,000 to €40,000, and we fit it as part of the same job.
The most popular flat roof extension idea in Dublin: a low, clean roof outside and a raised glass lantern over the kitchen island or dining table inside. It lifts the ceiling height and floods the middle of a deep room with daylight.
One long rooflight along the back wall of the house, or two or three square ones, keep the ceiling flat and the roofline slim. They cost less than a lantern and suit a narrower extension or a side extension along a boundary.
Slate or tile to match the house, with the ceiling following the slope of the roof inside. It suits cottages, bungalows and period homes, and Velux-style rooflights sit in the slope. Under the exemption it must stay below the highest part of the house roof.
Since 27 July 2026, Class 1 of the exempted development regulations covers a rear extension of up to 45 m² in total, up from 40 m², as long as it meets the height, garden and boundary rules.
Usually exemptUp to 45 m², walls no higher than the rear wall of the house.
Check firstEvery extension since 1964, and a converted garage, counts towards the 45 m².
Needs permissionClass 1 covers the rear only, so any part to the side needs planning.
The allowance is a total for the house, not for each extension, and the garden has to stay at 25 m² or more.
Example: a 10 m² utility added years ago plus a new 30 m² kitchen extension uses 40 of the 45 m².
Break one and the extension needs planning permission. The building regulations apply either way.
A rear extension is the quick, usually exempt route. A wrap-around gives more room and a better layout, at a higher rate and with a planning application.
Cost per m² in Dublin
Build costs at standard finish, including VAT, from our extension cost calculator. For a full cost breakdown see the house extension cost guide, and for ideas see kitchen extensions.
One team from the first visit to the handover, with about 12 to 16 weeks on site.
We walk the house and garden with you, look at drains, boundaries and any earlier extension, and talk through how you want the room to work.
Drawings, the engineer's design for the foundations and steel, and a written quote. For a side or wrap-around extension, the planning application goes in here, which adds about 12 to 16 weeks.
Site set-up, digging, drains and footings, then the floor slab at the level of the house.
Block walls, the steel beams, the roof and its rooflights or lantern, then windows and doors so the room is weathertight before we open into the house.
The rear wall comes down, then wiring, plumbing, heating, insulation, plastering, flooring, the kitchen and paint.
A full snag list, a clean, a walkthrough with you and the engineer's sign-off and certificates for your records.
Single-storey kitchen-diners on Dublin semis and terraces make up most of the extensions we build. We build it in block, keep your kitchen running for as long as we can, and back it with our 1-year workmanship warranty.
Whatsapp chatSee how we extend Dublin homes on one floor, with flat roofs, lanterns and wide glazing, 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 single-storey 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, and a single-storey side extension about €2,800 to €3,500 per m². A typical 20 m² rear extension comes to €54,000 to €69,000. Small extensions carry fixed costs for foundations, steel and the roof, so even one of up to 15 m² costs about €40,000 to €58,000. Fees (10 to 12%), a 15% contingency and a new kitchen are on top. Use the extension cost calculator or see extension cost by size.
Not for a single-storey rear extension of up to 45 m² in total, under the 2026 exempted development regulations (S.I. 338 to 344 of 2026), up from 40 m². You must keep at least 25 m² of private garden, the walls can be no higher than the rear wall of the house, and a flat roof can be no higher than the eaves or parapet. A side or wrap-around extension is not covered and needs planning permission. Read our guide to planning permission for extensions.
Yes, if it is built properly. A modern flat roof is laid to a gentle fall with a single-ply or fibreglass membrane over insulation, not the felt roofs that gave flat roofs a bad name in the 1970s. A flat roof keeps the extension below the first-floor windows and inside the exemption, and it takes a lantern or rooflights easily. Our flat roof extension guide compares EPDM, GRP and felt.
About 12 to 16 weeks on site, from the first dig to the handover. Before that, allow a few weeks for the survey, drawings, engineer's design and quote. If the extension needs planning permission, as a side or wrap-around one does, add about 12 to 16 weeks for the planning process before work can start.
Usually, yes. We build the new room up to a weathertight shell while the rear wall of the house is still in place, so your kitchen keeps working for most of the build. The disruption comes when we knock through and connect the new kitchen, which is a few weeks. Most families set up a temporary kitchen in another room for that stretch.
Yes, and it is one of the best ways to modernise a bungalow. Under the exemption, the extension's walls can be no higher than the bungalow's rear wall, so a flat roof with a lantern or rooflights is the usual answer, giving height and light inside without raising the roof. The same 45 m² limit applies. See our bungalow extension ideas for layouts.
No. Build Me builds single-storey extensions in traditional concrete block, on proper strip or raft foundations, finished to match your house. Timber frame and modular systems can be quicker to erect, but we build only in block. For a fair comparison of the two, read timber frame vs block extensions.
It depends on what you need. Per m², a two-storey extension is cheaper (about €2,200 to €3,100 against €2,700 to €3,400 in Dublin), but the total is higher and it usually needs planning permission. If the goal is a bigger kitchen and living space, a single-storey rear extension is quicker, usually exempt and less disruptive. Our house extensions page covers both, and kitchen extensions covers the kitchen side of the plan.
