Roof Structure in Ireland — Truss vs Cut Roof, Cost, and When Each Applies
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Truss roof: factory-made, fastest, cheapest. Cut roof: site-cut, more flexible, more expensive. Engineer specifies either way.
Truss roof: factory-made timber trusses, delivered to site and craned into place in 1–2 days. Fastest to erect, cheapest, standard for most Irish self-builds. Standard truss spacings: 400–600 mm. Trusses can be designed for most roof shapes (gable, hip, mansard, room-in-roof). Cut roof: site-cut timber rafters and ceiling joists, more flexible for complex shapes (curved, multi-level, dormers), more expensive. Engineer specifies either way. The roof structure must support the slate or tile (40–60 kg/m² for natural slate), the snow load (typically 0.75–1.0 kN/m² in Ireland), and the wind load on the county (varies by exposure). Building Regulations 2023 TGD-A (Structure) governs.
When this matters most
You're at design stage and need to specify the roof structure.
When this doesn't apply
The roof is on.
Sources
Building Regulations 2023, TGD-A (Structure). https://www.gov.ie/
Frequently asked questions
What is the cheapest roof structure in Ireland?
Truss roof. Factory-made, delivered to site, craned into place in 1–2 days. Standard for most Irish self-builds.
When is a cut roof used?
Complex shapes (curved, multi-level, dormers), heritage sites, or where the design doesn't suit a standard truss. More expensive than a truss roof.
How much does a truss roof cost in Ireland?
€50–€80/m² of roof area for the trusses, plus €30–€50/m² for the tiling/slating. For a 150 m² house: €12,000–€20,000 for the trusses and roof covering.
When this matters most
You're at design stage and need to specify the roof structure.
When this doesn't apply
The roof is on.
Where to go next
Next decision
The next step in your build sequence.
Branch into
Adjacent decisions at the same stage.
Watch out for
Common mistakes, hidden costs, gotchas.
- Concrete Tile Roof in Ireland — Cost, Lifespan, and When It's the Right Choice →
- Flat Warm Roof in Ireland — Construction, Cost, and Avoiding Condensation →
- Pitched vs Flat Roof in Ireland — Cost, Lifespan, and Which Suits Your Build →
- Rainwater Harvesting in Ireland — Cost, Rules, and Whether It's Worth It for a Self-Build →
- Ridge Ventilation in Ireland — Why It Matters, What It Costs, and the Building Regs →
- Roof Windows in Ireland — Velux, Keylite, and Fakro, Cost and Where to Use Them →
- Slate Roof in Ireland — Natural vs Man-Made, Cost, and the 100-Year Lifespan →
Compare with
Alternative approaches worth knowing.