Underpinning questions

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.

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.

In the UK, BRE's subsidence database found mass concrete underpinning the most common, often applied to only part of a building. We haven't found equivalent Irish figures.

No source we trust puts a number of years on it. Mass concrete underpinning is used where permanent support is needed. What matters later is that the cause was fixed, an engineer designed the work, and you keep the engineer's sign-off.

Yes, in many cases. A structural engineer told The Irish Times that a wall can be underpinned from the outside, with a mini-piling machine small enough to go through a front door.

It depends on the method. A piled raft means taking up the internal floors. Work from outside the walls can leave the inside alone. Ask the engineer and the contractor before you agree a start date.

TGD A notes that guidance written for new work can be unduly restrictive or impracticable for existing buildings, especially buildings of architectural or historical interest, and that approaches based on its principles may suit better. That is a job for an engineer with experience of older buildings.

Underpinning with small-diameter piles, normally 150 to 300 mm across, that carry the load of the house down to stable ground, usually more than 5 m down.

Yes. Companies offer geopolymer or resin injection in Ireland, and Irish engineers also describe grout being pumped into the ground under foundations.

Irish engineers say leaking drains cause most of it, especially old clay drains with unsealed joints. Trees drying the soil, weak or made ground, soft river and estuary deposits, and tunnelling or excavation nearby are other causes.

Cracks at about 45 degrees from the corners of windows and doors, doors and windows that stick or have been shaved to close, sloping floors, skirting boards that don't line up, and blocked drains.

Settlement is movement caused by the weight of the building itself, usually early in its life. Subsidence is the ground underneath moving down independent of the building's load. A surveyor or engineer tells them apart from the location and pattern of the cracks.

People do, with eyes open. A surveyor told The Irish Times that investigations and a drainage survey before contracts are essential, and the bank will want the reports. An Irish engineer warns that if you buy without advice, the problem becomes yours and is unlikely to be covered by your insurance.

No public record of subsidence pockets exists. Geological Survey Ireland's PanGeo maps cover Co. Dublin and Cork City, and GSI keeps karst and landslide data. None of it replaces an engineer looking at the house.

On BRE's scale, cracks up to about 5 mm are aesthetic, 5 to 25 mm are serviceability damage, and over 25 mm is a stability issue. A crack that keeps widening matters more than its size today.

BRE's category 0, hairline cracks under about 0.1 mm, is negligible and needs no action. Get advice if they keep growing, multiply, or run diagonally from the corners of openings.

Subsidence cracking is usually more severe and noticeable, and diagonal from the corners of windows and doors. A surveyor or engineer tells them apart from the location and pattern, and monitoring shows whether they're still moving.

Fill them last. Irish engineers repair cracks six months to a year after the cause has been fixed, once the building has settled.

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.

It's labour- and machine-intensive groundwork, done by a small number of specialist contractors with specialist equipment, according to an Irish building engineer. The drains, investigations and making good add to it.

If the damage was caused by an insured event such as subsidence, policies typically pay to repair the damaged part, including the foundations under it, less a subsidence excess. Exclusions apply. See the insurance guide.

We haven't found an Irish engineer's published fee for a subsidence assessment. The Irish Times put a ground investigation at around €3,000 in 2020, which is a larger piece of work than an initial inspection.

A company that sells it says it typically costs around half as much. We haven't found independent Irish figures to check that claim.

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.

The part of a subsidence claim you pay yourself. In one Irish policy it is one of four excesses shown on the schedule, separate from the general policy excess.

Not usually. Policies define settlement as movement from the building's own weight and exclude it, along with bedding down and defective foundations.

Yes. One Irish policy won't pay for subsidence damage if the building had it before, unless that was disclosed and accepted.

Some policies let the insurer arrange the repair or use its own network of building contractors. You can still ask for an independent price and discuss it with the insurer.

The insurer first. If you're not satisfied, the Financial Services and Pensions Ombudsman, which is independent and free.

No. Pyrite heave swells the hardcore under ground-floor slabs and pushes up. Underpinning supports foundations that have lost support below. The pyrite scheme deals with pyrite damage.

As published in 2020: Dún Laoghaire-Rathdown, Fingal, Kildare, Meath, Offaly, South Dublin, Dublin City, and Limerick City and County, added on 25 September 2020. Check the current list with the Pyrite Resolution Board.

Muscovite mica, a mineral, in concrete blocks. Too much of it makes the blocks absorb water, lose strength and crumble, especially through freeze-thaw. A 1% limit applies.

The enhanced Defective Concrete Blocks Grant Scheme covers Donegal, Mayo, Limerick and Clare, with grants of up to €420,000 depending on the works.

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.

It depends on the works. Notices are required for material alterations, among other things, and not required for works needing neither planning permission nor a Fire Safety Certificate. Ask your engineer, and lodge it 14 to 28 days before starting if one is needed.

The Land and Conveyancing Law Reform Act 2009 gives you a right to carry out works to a party structure, with duties to make good damage and pay the neighbour's reasonable costs of advice. If they refuse, you can apply to the District Court for a works order.

A chartered structural engineer. Engineers Ireland awards the CEng MIEI title. The HSA suggests checking membership of bodies such as Engineers Ireland or the Association of Consulting Engineers.

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.

No. Sending a request is free and you're not committing to anything.

No. Underpinning.ie is an introduction service, not an engineering firm. It does not inspect buildings or give structural advice. We pass your request to one experienced groundworks and underpinning contractor who covers your county.

No. We never diagnose a house or say whether it's safe. That's for a chartered structural engineer who has seen it.