Bottom-hung tilt-in window, made to measure

A bottom-hung window tilts open inward from the top, with the hinge on the sill. That is the exact opposite of a side-hung casement, which is hinged at the side. The practical result: you can fit a bottom-hung window high in a wall — above a basin, in a WC, above a kitchen worktop — and still operate it without a sash swinging into the room at head height. The opening is set to one fixed gap, not a range of positions as with tilting.

The standard size is 1,100 × 800 mm: wider than it is tall, to suit the narrow strips where a bottom-hung window usually goes. Choose one if you're mainly after ventilation in a spot where you rarely or never look out, and not if you also want to clean the glass from inside there — for that you need to be able to reach the window, as with a side-hung casement.

The 1,100 × 800 mm size fits a strip above tiling or above a fitted cupboard, which is exactly where a bathroom or WC often has its only outside wall. Because the pane is wider than it is tall, the sash stays light enough to operate with one hand, even with a long pole if the window sits really high. Put a bottom-hung window low, at eye level, and you lose the only advantage the form has — a standard tilt and turn window is then just as easy to operate and does more.

Within the window group, a bottom-hung window shares its hinge arrangement with nothing else: every other layout is hinged at the side or uses a fixed mullion. If you're after the same high, hard-to-reach spot but with more than just a gap, there is no alternative in this group — that is why the fixed window with tilt-in top light and the tilt and turn window with tilt-in top light put a bottom-hung sash above another pane rather than making a larger bottom-hung window: the form itself is tied to a small size.

When you order a bottom-hung window, the height it goes in at matters at least as much as the size of the pane itself: check how far the sash comes into the room when it is tilted open, because that is the space you need to keep clear below it — above a basin or a worktop nothing should stand in the way there. As with every other pane, you order to the overall size of the frame, not to an opening size.

Maintenance on a bottom-hung window centres on the hinge at the bottom and the operating rod: the rod is an extra part a standard side-hung casement doesn't have, and it's worth checking that it runs smoothly alongside the usual check of the hardware. Colour and finish follow the same chart as any other window — any RAL colour on aluminium, a foil or through-colour on uPVC. Because a bottom-hung window usually sits high and so less in direct view on the elevation, many people deliberately choose the same colour as the nearest larger window here, so the elevation reads as one and the small window doesn't stand out as a separate element.

In a bathroom renovation, a bottom-hung window often replaces an existing high window without the tiling or the fitted units having to move — the size stays modest and the position doesn't change. In a new build this layout is often planned in from the start for WCs and utility rooms, precisely because the architect can then allow for the height at which it works best, rather than fitting it afterwards into an elevation that has already been fixed.

For break-in resistance, a bottom-hung window usually plays a smaller part than a ground-floor window: placed high, it is harder to reach from outside. That doesn't mean the hardware needs no attention — here too, ask about the standard locking hardware if the spot can be reached after all, for example from an extension roof.

The weight of the glass counts when you choose it, although a bottom-hung window is less sensitive to heavy glass than a large side-hung casement because of its small size. If you do choose the heaviest glass, the configurator checks whether the hardware can take it at the size you enter.

Still not sure? Use the comparison with the other layouts in this group above to see which arrangement suits your situation best.