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.
TL;DR
Truss roof: factory-made timber trusses, fastest to erect, cheapest, standard for most Irish self-builds.
Cut roof: site-cut timber rafters and ceiling joists, more flexible for complex shapes, more expensive.
Engineer specifies either way. The roof structure must support the slate or tile, the snow load, and the wind load on the county.
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.
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.
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.