Basement conversion

Converting an existing basement or cellar into a finished room costs €1,000 to €2,500 a m², or €30,000 to €100,000 for most whole basements. Most take 6 to 12 weeks.

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€1,000 to €2,500a m², all in, for most conversions
€30,000 to €100,000for most whole basements
6 to 12 weeksstart to finish
10 to 15%to keep aside for what's found once walls are opened

Basements and cellars

A white terrace of period town houses with black railings and basement areas along a stone pavement — **Period houses.** Period town houses with basement areas behind the railings

Narrow steps leading down between black railings to a red basement door — **Basement flats.** Steps down to a basement door, below street level

Brick steps with a handrail leading down into a lit vaulted brick cellar — **Cellars.** Brick steps down into a vaulted cellar

What a conversion involves

A survey. Where water gets in, how wet the walls and floor are, the head height, the stairs, and whether there's room for light and a way out.
Strip out. Old plaster, timber and floor finishes come out. Rotten timber goes.
Waterproofing. Slurry tanking on sound walls, or a cavity drain membrane that leads water to a sump. See tanking vs cavity drain membrane.
Radon. A barrier and a sump, or a plan to test and add a fan. Basements sit closest to the ground.
Insulation and boarding. A heated room has to meet Part L, so the walls and floor are insulated.
Light, air and a way out. Light wells or bigger windows, ventilation, and an escape route for a room you'll sleep or sit in.
Finish. Electrics, heating, the floor and the decoration.

Four things to check first

Head height. Most designers aim for at least 2.4 m from the finished floor to the ceiling in a room you'll live in. Waterproofing, insulation and a new floor take some of what's there. Less than that means lowering the floor: see digging out.
Water. A basement that floods after heavy rain needs a drained system and a sump, not paint-on sealer.
A way out. A bedroom or living room below ground needs a safe escape route. See the Building Regulations.
Planning. Inside an existing basement, usually none. New openings at the front or a protected structure: ask the council. See planning permission.

What it costs for your size

Two taps: the job and roughly how big the basement is. The answer comes from our price guide.

The job

Convert an existing basementInto a finished roomWaterproof (tank) itDamp or water coming inDig a new basementOr lower the floor

Floor area, roughly

Typical range

€30,000 to €75,000

30 m² at €1,000 to €2,500 a m², the usual range to turn an existing basement into a finished room. Tanking with a membrane and a sump is often priced on top, at €3,000 to €12,000.

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How this is worked out

For a conversion or a dig-out, the floor area times our range a m² (€1,000 to €2,500 to convert, €3,000 to €6,000 to dig). For tanking, the typical price for a basement that size. It's a guide, never a quote: the company prices your basement after a look. Building work on a house is charged VAT at 13.5%. Ask whether the written price includes it.

Related guides

Basement conversion and waterproofing guides & price breakdowns

Straight answers to what people ask most: itemised costs, specifications, planning or grants, and what to check before you book.

Cost & Pricing GuideBasement conversion cost in IrelandBasement conversion cost in Ireland: €1,000 to €2,500 a m², €30,000 to €100,000 for most. Tanking €50 to €180 a m². Our price guide and one free quote.Read the guide →Specification GuideBasement sump pumpsBasement sump pumps in Ireland: €1,000 to €2,000 for a sump system. How a sump works, two pumps, battery back-up, alarms and servicing. One free quote.Read the guide →Comparison GuideTanking vs cavity drain membraneTanking vs cavity drain membrane for a basement in Ireland: how each works, which suits a wet basement, costs, sumps and guarantees. One free quote.Read the guide →Grants & RegulationsBuilding Regulations for a basementBuilding Regulations for a basement in Ireland: escape in a fire (Part B), radon and damp (Part C), ventilation (F), insulation (L), structure (A).Read the guide →Specification GuideRadon and basementsRadon in basements in Ireland: the 200 Bq/m³ reference level, High Radon Areas, radon sumps (€500 to €2,000) and testing. One free quote.Read the guide →Timeline & PreparationHow long a basement conversion takesHow long a basement conversion takes in Ireland: 6 to 12 weeks for most, waterproofing 1 to 2 weeks, finishing 2 to 3 weeks. Digging out takes longer.Read the guide →

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Questions we get asked

Can any cellar be converted?

Most can, if there's enough head height or the floor can be lowered, and the water can be managed. A survey answers both.

Can a basement be a bedroom?

Yes, with a safe way out in a fire, enough light and air, and a dry, warm room. The Building Regulations set the rules for escape and ventilation.

Does a basement conversion add value?

A dry, bright, legal room adds usable space. A damp one with no escape route doesn't. Do it properly or not at all.

What's the difference between a cellar and a basement?

Mostly words. A cellar is usually a small, low storage space; a basement is a full storey below ground. The same waterproofing applies to both.

Basement conversion and waterproofing across all 26 counties

Requests from all 26 counties go to one vetted local specialist who covers your county — from Dublin, Cork, Galway and Limerick to Kildare, Meath, Wicklow, Waterford and Donegal. Pick your county below for local prices, specifications and advice. Compare all areas covered →

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