Mini-piling, Dublin semi
€16,000
April 2020, trade rates
Piles 6 m deep under one house in Rathgar, costed by a structural engineer at about 20% below retail. The Irish Times.
Underpinning and subsidence · Ireland
Underpinning in Ireland, engineer first
Cracks, sloping floors or doors that won't close can mean the ground under a house has moved. Underpinning puts new support under the foundations, and it starts with a structural engineer, never a guess. Tell us what's happening and one experienced groundworks and underpinning contractor who covers your county rings you.
- Engineer's assessment first
- One contractor rings you, not a list
- Every fact sourced and dated
Underpinning a building in stages, one pit at a time. Photo: Patrick Oberdörfer, CC BY-SA 4.014 counties, engineer first
Underpinning
Real underpinning, real foundations
Mass concreteDug and filled in bays
The methodsFour ways, chosen by the engineer
The processFrom the first crack to sign-off
Underpinning costEvery published Irish figureReal foundation work from Wikimedia Commons: underpinning a building in stages, by Patrick Oberdörfer (CC BY-SA 4.0); temporary underpinning, a steel beam carrying a brick wall, by Jkg52-wiki (CC BY-SA 4.0); an underpinning pit being dug, by MTA Capital Construction Mega Projects (CC BY 2.0); concrete going into an underpinning pit, both at the 39th Street Bridge, by MTA Capital Construction Mega Projects (CC BY 2.0). None of them is a job passed on through this site.
Underpinning.ie
New support under the foundations, once an engineer says so
Underpinning strengthens the foundation of an existing building by taking it deeper or wider, so it rests on firmer ground or spreads its load further (Wikipedia). In Irish houses it mostly follows subsidence: the ground under part of the house stops supporting it evenly, that part drops a little, and walls crack (Irish Examiner).
Most cracks are not subsidence. BRE Digest 251, the scale engineers use, treats cracks up to 5 mm as aesthetic. And when it is subsidence, Irish engineers say old leaking drains are usually behind it, so the drains get fixed first.
Underpinning.ie passes requests to one experienced groundworks and underpinning contractor who covers your county. They ring you, ask what's happening and about any engineer's report, and price the work from the engineer's design. Read house subsidence and when underpinning isn't needed.
This site never tells anyone their house is safe or that it needs underpinning. A chartered structural engineer who has seen the house decides.
Methods
Four ways to underpin a house
- Mass concreteBays dug under the footing and filled with concrete. The traditional method at shallow depths.
- Beam and baseA reinforced concrete beam carries the wall to concrete bases sized to the ground.
- Mini-piledSmall piles, 150 to 300 mm across, down to stable ground, often more than 5 m below.
- Resin and grout injectionStrengthening the ground under the footing through small holes, once the cause is fixed.
Cracks
How engineers grade cracks
BRE Digest 251 sorts cracks into six categories by width and damage. It's the scale Irish engineers and surveyors use. Width isn't everything: a crack that's still growing matters more.
| Category | Typical crack width | What it means | Group |
|---|---|---|---|
| 0 | Hairline, under about 0.1 mm | Negligible. No action needed. | Aesthetic |
| 1 | Fine, up to about 1 mm | Treated with normal decoration. Usually internal finishes only. | Aesthetic |
| 2 | Up to about 5 mm | Easily filled. Some external repointing may be needed. Doors and windows may stick slightly. | Aesthetic |
| 3 | 5 to 15 mm, or several of about 3 mm | Some opening up and patching by a mason. Doors and windows stick, service pipes may fracture. | Serviceability |
| 4 | 15 to 25 mm, depending on number | Sections of wall broken out and replaced. Frames distorted, floors sloping noticeably, walls leaning or bulging. | Serviceability |
| 5 | Over 25 mm, depending on number | Major repair, partial or complete rebuilding. Walls lean badly and need shoring. Danger of instability. | Stability |
Source: BRE, Assessing cracks in houses, setting out the categories in BRE Digest 251. BRE stresses this is a simplification: whether cracks are widening over time also matters.
Costs
What's actually published in Ireland
No Irish contractor or public body that we could find publishes an underpinning price list. These are the dated Irish figures that exist.
Ground investigation
€3,000
About, April 2020
Trial holes to find how deep firm ground is. The same engineer's estimate. The Irish Times.
CCTV drain survey
€385
Incl. VAT, April 2020
One drain company's pre-purchase survey with maps of the drains. The Irish Times.
Insurer retention
5% / 10%
Under / over €40,000
What an insurer can hold back until the repair is done and invoiced. Aviva policy booklet.
Checked 29 October 2026. These are dated figures for particular jobs, not a price list. The cost guide.
How it works
From the first crack to sign-off
The order Irish engineers describe. Nothing is booked until you say yes.
- Record the cracksDated photos, inside and out, with a ruler in the shot. Don't fill them yet.
- Engineer's assessmentA chartered structural engineer grades the cracks and finds the cause, usually the drains.
- Fix the cause, then the designOld clay drains replaced with sealed uPVC. The engineer designs the underpinning, and the contractor prices and builds it.
- Settle, then repairCracks filled six months to a year later. Keep the engineer's sign-off.
We don't inspect houses or do building work. We pass your request to one experienced groundworks and underpinning contractor who covers your county. The full process, step by step.
Before anything else
Five things to do first
From Irish engineers writing in the Irish Examiner and quoted in The Irish Times, and the claims conditions in an Irish home insurance policy.
- Photograph and date every crack
- Don't fill them yet
- Get a chartered structural engineer
- Have the drains checked
- Tell your insurer early if you're claiming
Guides
Underpinning and subsidence guides
- House subsidenceWhat it is, why Irish houses get it, the signs.
- Subsidence cracksThe BRE scale, patterns, monitoring.
- The processTen steps from first crack to sign-off.
- Underpinning costEvery published Irish figure, dated.
- Subsidence insuranceDefinitions, exclusions, retentions, complaints.
- Pyrite and defective blocksWhy underpinning doesn't fix them.
Counties
Underpinning by county
Each county page has the age of its housing from Census 2022, its ground, and the schemes that apply. The figure is the share of households in homes built before 1971. Compare all 14.
FAQ
Underpinning questions
What is underpinning?
Strengthening the foundation of an existing building by making it deeper or wider, so it rests on firmer ground or spreads its load over a bigger area. The main methods are mass concrete, beam and base, mini-piles and injection.
Does my house need underpinning?
Only a chartered structural engineer can say, after looking at the cracks, the ground and the drains. Most cracks don't mean underpinning: BRE's scale treats cracks up to 5 mm as aesthetic.
How much does underpinning cost in Ireland?
No Irish contractor or public body that we could find publishes a price list. The one published Irish figure is €16,000 for mini-piling under a semi-detached house in Dublin 6 in 2020, at trade rates. Your price comes from your engineer's design.
Does home insurance cover subsidence?
The Irish policies we've read list subsidence, ground heave and landslip as insured events, with a separate subsidence excess and a list of exclusions. Check your own booklet.
How long does underpinning take?
It depends on the method and the house. The cracks aren't repaired until six months to a year after the works, so the whole process from first crack to finished repair can run over a year.
Who will ring me?
We pass your request to one experienced groundworks and underpinning contractor who covers your county. Your number isn't sent to a list. They ring you, ask what's happening and about any engineer's report, and price the work from the engineer's design. Nothing is booked until you say yes.
Get a quote
Tell us what's happening in 4 quick taps
It goes to one experienced groundworks and underpinning contractor who covers your county, and they ring you to talk it through. They'll ask about any engineer's report.
Where these facts come from (7 public sources, checked 29 October 2026)
Sources (1)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Aviva policy booklet: arachas.ie