Piled Raft Foundation in Ireland — For Peat, Made Ground, and Soft Clay Sites
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Piled raft on Class 5+ ground: €280–€450/m². Piles transfer the load to a firm bearing stratum below the poor soil.
A piled raft foundation in Ireland is required when the soil near the surface cannot support the building. Piles are driven or bored to a firm bearing stratum, then a reinforced concrete slab caps them. €280–€450/m² of footprint. A 150 m² house: €42,000–€67,500. The site investigation (€1,500–€3,000) confirms the depth of poor soil and the bearing stratum. Engineer-led design is mandatory — piles must be designed and signed off by a chartered engineer with pile-driving experience. Common on infill sites in former bogs, made ground on reclaimed land, and any site with more than 2 m of soft clay or peat over rock. Building Regulations 2023 TGD-A (Structure) governs the structural rules.
TL;DR
Piled raft foundation in Ireland: €280–€450/m² of footprint. Required for Class 5+ ground (peat, made ground, soft clay, fill).
A 150 m² house on piled raft: €42,000–€67,500. Piles are driven or bored to a firm bearing stratum, then a reinforced concrete slab caps them.
Engineer-led design. Piles must be designed and signed off by a chartered engineer with pile-driving experience.
When this matters most
Your site has Class 5+ ground (peat, made ground, fill) or significant fill that won't support a raft.
When this doesn't apply
Your site has Class 1–4 ground. A strip or raft is cheaper.
Frequently asked questions
How much does a piled raft cost in Ireland?
€280–€450/m² of footprint. For a 150 m² house: €42,000–€67,500. Includes piles and the capping slab. Engineer design is mandatory.
When is a piled raft needed?
Class 5+ ground: peat, made ground, soft clay, fill. Common on infill sites in former bogs, reclaimed land, and any site with more than 2 m of poor soil over rock.
How deep are piles in Ireland?
Site-specific. Typically 4–15 m for residential. Driven piles are faster; bored piles are quieter. Engineer specifies depth based on the site investigation.
Sources
Building Regulations 2023, TGD-A (Structure). https://www.gov.ie/
Frequently asked questions
How much does a piled raft cost in Ireland?
€280–€450/m² of footprint. For a 150 m² house: €42,000–€67,500. Includes piles and the capping slab. Engineer design is mandatory.
When is a piled raft needed?
Class 5+ ground: peat, made ground, soft clay, fill. Common on infill sites in former bogs, reclaimed land, and any site with more than 2 m of poor soil over rock.
How deep are piles in Ireland?
Site-specific. Typically 4–15 m for residential. Driven piles are faster; bored piles are quieter. Engineer specifies depth based on the site investigation.
When this matters most
Your site has Class 5+ ground (peat, made ground, fill) or significant fill that won't support a raft.
When this doesn't apply
Your site has Class 1–4 ground. A strip or raft is cheaper.
Where to go next
Branch into
Adjacent decisions at the same stage.