Method · checked 29 October 2026
Resin and grout injection
Strengthening the ground under a footing through small holes, without digging it out. What it is, and its limits.
Facts on this page checked against each source on 29 October 2026. Each one links to its source. How we check
Injection underpinning strengthens the ground under a footing by pumping material into it through small holes, instead of digging out and replacing it. Irish engineers describe grout being pumped into the affected ground to restore its strength (Irish Examiner, 2022). Companies also inject expanding resins or geopolymers.
Grout injection
Writing in the Irish Examiner, building engineer Kieran McCarthy describes underpinning in a typical Cork subsidence repair as liquid concrete (grout) pumped into the affected area to reintroduce the compressive strength the ground has lost. In an earlier column he describes a "pin" of reinforced concrete grout drilled and pumped into the ground under the foundation (Irish Examiner, 2022, 2021).
Pressure grouting can be low or high pressure. Low pressure chemical injection grouting is used to underpin structures in sandy soils (Wikipedia).
Resin and geopolymer injection
One company that offers it in Ireland, Geobear, describes its process like this: scan for services and mark the drilling points, drill to the treatment depth, insert tubes, inject the geopolymer at the levels set in a plan, and watch the foundation's movement with laser levels as it goes in. It says residential jobs take one or two days and that its method typically costs around half as much as traditional underpinning (Geobear). Those are the company's own claims. We have not seen independent Irish figures to test them.
When injection may not be the answer
- A leaking drain is still leaking. In the repairs Irish engineers describe, the old clay drains are dug out and replaced as part of the job (Irish Examiner, 2022). Treating the ground without fixing the drain treats the symptom.
- Firm ground is a long way down. When the load has to go to stable ground at depth, piles are the usual method (Wikipedia).
- It isn't subsidence. Pyrite heave lifts floor slabs from below, and defective blocks fail in the walls themselves. See pyrite and defective blocks.
Questions to ask
- What material is being injected, and to what depth?
- What did the ground investigation find, and does injection suit it?
- How are levels monitored during the work?
- What happens to the drains?
- Who designed it: an independent chartered engineer, or the company doing the work?
- Will a chartered engineer certify the finished work, so you have it when you sell?
Questions people ask
Is resin injection underpinning available in Ireland?
Yes. Companies offer geopolymer or resin injection in Ireland, and Irish engineers also describe grout being pumped into the ground under foundations.
Is resin injection cheaper than traditional underpinning?
One company that sells it says so, typically around half the cost. We haven't found independent Irish figures to check that claim.
How long does injection take?
The same company says most residential jobs take one or two days. Your contractor can say for your house.
Does injection fix the cause of subsidence?
Not on its own. If a leaking drain softened the ground, the drain needs fixing too, which is part of the Irish repairs described by engineers.
Related
Keep reading
Sources (1)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Geobear: residential.geobear.com
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