Roof Replacement glossary of terms & specifications

15 technical terms, material grades and Irish standards explained in plain English so you know exactly what is on a written quote.

Sorted A to Z for quick reference when comparing specifications.

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Key roof replacement terms explained

Blue Bangor Welsh Slate

Hand-split natural metamorphic slate quarried in North Wales (500x250mm or 600x300mm), widely required on Victorian and Georgian period re-roofs and Architectural Conservation Areas across Ireland with a working life of 80 to 100+ years.

Breathable Breather Membrane (Sarking Felt)

Vapour-permeable, watertight underlay laid over the rafters under IS EN 13859-1 that allows internal roofspace moisture to escape while stopping wind-driven rain and snow.

C24 Kiln-Dried Treated Timber Battens

Structural softwood tiling and slating battens pressure-treated to Use Class 2 ( typically 50x25mm or 38x25mm) graded to IS EN 14081 and fixed to rafters with hot-dip galvanised or stainless nails.

Code 4 and Code 5 Rolled Lead Flashing

Milled lead sheet to BS EN 12588 used at chimneys, valleys, abutments and dormers; Code 4 (1.80mm, green) suits standard flashings and aprons while Code 5 (2.24mm, blue) is specified for valley gutters and back gutters.

Cold Roof vs Warm Pitched Roof

In a cold pitched roof, mineral wool or cellulose insulation sits at ceiling joist level (targeting U-value 0.16 W/m2K) with cross-ventilation above; in a warm roof or room-in-roof, PIR boards sit at rafter level targeting 0.18 W/m2K.

Counter-Batten

Timber batten fixed vertically down the line of each rafter above a taut breathable membrane to preserve an unobstructed 25mm drainage and ventilation air path beneath the horizontal tiling battens.

Dry Verge and Dry Ridge System

Mechanically fixed ridge, hip and gable verge units complying with BS 8612 that replace traditional sand-and-cement mortar bedding, resisting Atlantic wind uplift without cracking.

Eaves Ventilation Tray (Raflo / Roll-Out Rafter Tray)

Corrugated PVC tray fitted between rafters at the eaves to stop loft quilt insulation blocking the 10mm or 25mm continuous soffit air intake gap.

Fibre-Cement Slate (Tegral / SVK Thrutone)

Manufactured autoclaved fibre-cement roof slate (typically 600x300mm) finished with an acrylic coating, carrying a 20-year structural and 10-year colour guarantee at roughly €110 to €135/m2 installed.

Hipped Roof vs Gable-to-Gable Roof

A gable roof has two pitched slopes meeting at a single horizontal ridge between masonry gable walls, whereas a hipped roof has four pitched slopes meeting at inclined hip rafters requiring extra hip cutting and dry-hip track.

HSA Working at Height & GA3 Scaffolding Inspection

Health and Safety Authority safety requirement under the 2006 Construction Regulations mandating edge protection, a written Construction Stage Safety Plan, and a formal GA3 scaffold register inspection before use and every 7 days.

Interlocking Concrete Roof Tile

Profiled or flat interlocking concrete tile (such as Roadstone or Breedon double roman or flat-profile tile) laid on 38x25mm or 50x25mm battens with a typical 50 to 60 year lifespan.

S.R. 82:2017 (Irish Slating and Tiling Code of Practice)

NSAI Standard Recommendation governing roof pitch limits, headlap, nail and clip fixings, wind-load zones, and underlay installation for slated and tiled pitched roofs in Ireland.

TGD Part L 25% Thermal Upgrade Rule

Building Regulations Technical Guidance Document L requirement triggered when more than 25% of a roof's surface area is stripped and replaced, requiring loft or rafter insulation to be brought up to 0.16 W/m2K (ceiling) or 0.18 W/m2K (rafter) where feasible.

Two-Thirds VAT Rule (13.5% vs 23%)

Revenue Commissioners rule applying the reduced 13.5% VAT rate to the entire domestic re-roofing invoice provided the cost of materials excluding VAT does not exceed two-thirds (66.7%) of the total contract price.

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Questions people ask

How much does a new roof cost in Ireland?

On a two-storey semi, €8,500 to €15,000 in concrete tile, €9,000 to €17,000 in fibre cement slate and €16,000 to €24,000+ in natural slate. A detached house is €11,500 to €32,000+. The cost guide breaks it down by house, material and county.

Why do roof quotes vary so much?

Because they often price different jobs. One includes new battens, a breathable membrane, lead flashings, scaffolding, the skip and VAT; another leaves half of it out. The company we pass you to puts every item in writing, so you can see what you're paying for.

How long does a new roof take?

Three to ten working days on most houses, weather allowing, plus a day either side for the scaffolding. The roof is made weather-tight every evening. See how long it takes.

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