Raised attic flooring over 300mm insulation (BER-safe boarding).
Squashing 300mm of mineral wool down into a 100mm ceiling joist bay cuts its thermal resistance (R-value) by more than 50% and traps moisture.
Whether you have just had an SEAI attic insulation upgrade or are topping up an older roof space, here is how raised boarding keeps your BER certificate and ceiling joists safe.
Free, no obligation. One local attic flooring specialist prices your job, not five.
- 300mm WoolSEAI standard quilt depth preserved
- 0.16 W/m²KTarget ceiling U-value maintained
- 25–50mm GapBreather gap beneath T&G deck
- €55–€85/m²Supplied & fitted across Ireland
2026 Irish Price & Specification Table
Why you must never compress 300mm mineral wool
Mineral wool, glasswool and sheep's wool insulate by trapping still air pockets between fibres. Crushing those pockets under chipboard destroys both heat retention and vapour permeability.
| Job / Package | Typical 2026 Price | What Is Included |
|---|---|---|
| Raised loft boarding + Stira stairs package (15–25 m²) | €950 to €2,400 | Our most popular 1-day package: 270mm XL Loft Legs over 300mm mineral wool, 18mm P5 T&G chipboard deck, and insulated folding timber attic stairs. |
| Raised attic flooring on Loft Legs / XL Legs (supply & fit) | €55 to €85 a m² | Elevates the floor 175mm–300mm above ceiling joists so 300mm quilt insulation stays uncompressed and SEAI BER ratings are protected. |
| Structural timber counter-batten raised deck (175×44mm) | €70 to €105 a m² | Cross-battened C16 treated timber joists fixed perpendicular to ceiling ties for heavier storage loads and older cut-roof attics. |
| Standard T&G boarding directly onto deep joists | €42 to €62 a m² | Only suitable where ceiling joists are already 250–300mm deep or where rafter insulation is used instead of joist wool. |
| Stira-style insulated folding timber attic stairs (supplied & fitted) | €350 to €650 | EN 14975 3-section folding pine/beech ladder (150kg–160kg rating), insulated airtight trapdoor (U-value 0.55–0.85 W/m²K) and architrave. |
| Attic hatch enlargement, relocation or new opening | €180 to €340 | Trimming ceiling joists, fitting double timber trimmers, plasterboard making-good and draught-proof perimeter seals. |
| Heavy-duty concertina aluminium loft ladder (narrow landing) | €520 to €850 | Die-cast aluminium scissor ladder for tight box-room landings or high floor-to-ceiling heights up to 3.3m. |
| LED loft batten tube light + pull-cord/landing switch | €95 to €180 | 4ft or 5ft 18W–36W daylight LED vapour-proof batten wired to your upstairs lighting circuit. |
| Safety grab rail / timber hatch balustrade & eaves shelving | €140 to €320 | Perimeter handrail around the open hatch plus raised side-truss shelving bays. |
Technical Breakdown
Engineering specification for raised loft boarding
Thermal conductivity & R-value loss
Uncompressed 300mm mineral wool (lambda 0.044 W/mK) delivers an R-value of 6.80 m²K/W (U-value ~0.15 W/m²K). Compressing that same roll under boards down to 100mm joist depth drops the R-value to ~2.70 m²K/W — equivalent to throwing away two-thirds of your top-up layer.
Interstitial condensation prevention
Warm water vapour rises through plasterboard ceilings in winter. When loft boards are pressed tight into insulation, moisture condenses on the cold underside of the chipboard, causing black mould and wet rot. A 25mm–50mm air gap under raised Loft Legs lets vapour disperse into the ventilated roof space.
175mm vs 300mm XL Loft Legs
Standard 175mm Loft Legs combined with a 100mm ceiling joist give 275mm clearance — ideal for 250mm–270mm insulation. Where full 300mm–350mm SEAI insulation is fitted, 300mm XL Loft Legs or Loft Leg + timber bearer grids provide a full 400mm height above the plasterboard.
Point-load & UDL capacity
Manufacturer-tested polypropylene Loft Legs installed at 400mm–600mm centres on structural ceiling joists support a uniformly distributed storage load (UDL) of 25 kg/m² to 50 kg/m² plus a technician or homeowner walking across the 18mm P5 tongue-and-groove deck.
Calculate your attic flooring & stairs cost
Two taps: pick your approximate loft area and whether you need raised boarding over insulation, a Stira stairs package, or both.
Your attic area × our 2026 Irish price guide
€1,480 to €2,320
20 m² at €55–€85/m² plus €380–€620 for the insulated folding attic stairs & draught-proof hatch.
- Raised Loft Legs keep 300mm mineral wool uncompressed so your BER rating and SEAI grant compliance are protected.
- All panels are 18mm P5 moisture-resistant tongue-and-groove loft chipboard fitted in 1 day.
How this estimate is worked out
Our calculator multiplies your floor area by 2026 Irish supply-and-fit rates: €55–€85/m² for raised loft boarding on 175mm–300mm Loft Legs over mineral wool, €70–€105/m² for structural counter-battened decks, plus €380–€650 where an EN 14975 insulated folding attic stairs is included.
Get a free quote for your attic floor & stairs
Four quick taps and your number. Your request goes to one local attic flooring & loft boarding specialist covering your county, who rings you back with a fixed written price.
Raised Attic Flooring Over Insulation questions answered
Will raised attic flooring affect my SEAI home energy grant?
No — provided the boarding is raised on Loft Legs or counter-battens so the full 300mm mineral wool layer remains uncompressed and a continuous ventilated air gap is maintained beneath the boards, your SEAI grant and post-works BER assessment are 100% protected.
Can you fit raised boarding if 300mm insulation is already rolled out?
Yes. The installer parts the top cross-layer of mineral wool along the joist lines, screws the Loft Legs directly into the timber ceiling joists, relays the wool snugly around each leg without gaps, and fixes the 18mm T&G deck on top.
What boards are used on top of Loft Legs?
Irish specialists use 18mm P5 moisture-resistant tongue-and-groove chipboard loft panels (typically 1220×325mm or 2400×600mm depending on hatch size), glued and countersunk-screwed in a staggered bond.
Can PIR insulation boards be used instead of Loft Legs?
Walk-on polyisocyanurate (PIR) foil-backed boards with bonded chipboard can be used, but they cost roughly twice as much per m² and must be taped carefully so moisture does not get trapped between vapour barriers.
Related attic flooring guides
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Attic flooring & Stira stairs across all 26 counties
Requests from all 26 counties go to one local attic flooring and loft ladder installer covering your county — from Dublin, Cork, Galway and Limerick to Kildare, Meath, Wicklow, Louth, Waterford and Donegal. Pick your county below for local prices, housing stock data and specifications. Compare all 26 counties covered →
Get a free quote for your attic floor & stairs
Four quick taps and your number. One local attic flooring & loft boarding specialist covering your county rings you with a fixed written price. Nothing is booked until you accept it.