Top-hung vs side-hung casements & Part B fire-escape rules
Most Irish casement windows combine a large side-hung sash (for full ventilation and Part B emergency fire escape) with a smaller top-hung fanlight or fixed pane so you can air the room in wet weather without rain blowing indoors.
How to plan your opening configurations room by room, and the exact Irish Building Regulations Part B rules for upstairs and downstairs bedrooms.
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Side-hung, top-hung and French casements compared
| Casement opening style | How it opens | Best rooms & use case |
|---|---|---|
| Side-hung casement | Hinged on left or right; swings out up to 90° on egress friction stays | Bedrooms (mandatory for Part B fire escape) & tall living room windows |
| Top-hung (awning) casement | Hinged at the top; bottom pushes out 15° to 45° | Bathrooms, kitchens & high fanlights — lets steam out while keeping rain off the cill |
| French casement (floating mullion) | Two side-hung sashes meet in the middle with no fixed centre post | Wide, shallow bedroom windows that could not meet the 450mm width rule with a fixed centre post |
| Fixed pane + top/side opener combo | One dead-light picture pane paired with one or two opening casements | Living rooms and dining rooms — maximises clear glass and cuts hardware cost |
Irish Building Regulations Part B bedroom fire-escape requirements
Under Ireland's Technical Guidance Document B (Fire Safety — Dwelling Houses), every habitable bedroom that does not open directly onto a final exit must have at least one emergency escape casement window meeting all four measurements:
- Minimum clear area: At least 0.33 m² of unobstructed openable area.
- Minimum clear width and height: At least 450mm wide by 450mm high when the sash is open (note: 450mm × 450mm equals only 0.20 m², so if the opening is 450mm wide it must be at least 735mm high to reach 0.33 m²).
- Cill height from bedroom floor: The bottom of the clear opening must sit between 800mm and 1,100mm above the finished bedroom floor level.
- 90-degree egress friction hinges: Standard friction stays stop at 55–60 degrees and project the sash into the middle of the gap. Bedroom fire-escape windows must use 90-degree egress hinges (and Easy-Clean sliding sliders so you can also clean the outside glass from indoors).
Part K child-safety restrictors vs fire escape
Where an upstairs window cill is close to floor level or accessible to young children, restrictor stays limit initial opening to 100mm. On a bedroom fire-escape window, the restrictor must be an auto-resetting thumb-release catch that an adult can release in one second without a key in an emergency—never a key-locked restrictor that traps occupants if the key is misplaced.
What casement windows cost in Ireland
Our supply-and-fit price guide per window and for a full 3-bed semi, before and after the SEAI grant.
| Job | Typical cost | What moves the price |
|---|---|---|
| White uPVC casement window (double glazed, A-rated) | €350 to €850 per window | Uw ≤ 1.4 W/m²K · side-hung or top-hung |
| Coloured or triple-glazed uPVC casement (0.8 W/m²K) | €550 to €1,100 per window | Anthracite grey / dual-foil or 40mm–44mm triple unit |
| Flush sash casement window (flush exterior) | €750 to €1,300 per window | Sash sits flush in frame · mechanical timber-look joints |
| Thermally broken aluminium casement | €700 to €1,550 per window | Slim 50mm–65mm sightlines · powder-coated RAL finish |
| Timber-aluminium alu-clad casement window | €1,100 to €1,950 per window | Engineered pine or oak inside, maintenance-free alu outside |
| Full 3-bed semi (8–10 casement windows), white uPVC | €4,500 to €8,800 | After €3,000 SEAI grant (if eligible): €1,500 to €5,800 |
| Full 3-bed semi (8–10 windows), flush casement | €6,800 to €11,500 | After €3,000 SEAI grant: €3,800 to €8,500 |
| Full 3-bed semi (8–10 windows), aluminium | €9,000 to €15,500 | After €3,000 SEAI grant: €6,000 to €12,500 |
Real examples and installation detail
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Questions homeowners ask
Can a top-hung window be used as a bedroom fire escape in Ireland?
Almost never. A top-hung awning sash hangs down across the top of the opening and blocks a firefighter carrying breathing apparatus. Bedroom escape windows should always be side-hung on 90-degree egress stays or French casements.
What are Easy-Clean egress hinges?
Easy-Clean egress hinges open to a full 90 degrees for emergency escape, and also have two small sliding buttons in the track that let you slide the open sash 120mm towards the centre of the window so you can reach your arm out and wipe the external glass safely from inside an upstairs bedroom.
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