Guide · VELUX Window Installation
Roof window handles, catches and child safety
The ironmongery on a roof window does three separate jobs, and it is worth separating them before choosing anything. It holds the sash shut against wind, it controls how far the sash can travel when open, and on some units it locks the window against a child opening it at all. Those are three different mechanisms, and a window can have the first without the second or third.
In a room a child uses, the specification is settled at order rather than solved afterwards with a plastic accessory. This page covers where the handle sits on each type, what a restrictor actually restricts, how a pivoting sash behaves in a room, and what Building Regulations ask of glazing near floor level.
Where the handle sits, and the two arrangements in use
There are two conventions and they lead to quite different rooms. A control bar across the top of the sash is operated by reaching up and pulling, which suits a window set high in a slope and means the handle is above a small child’s reach by design.
A handle at the bottom of the sash is operated by reaching forward at cill level, which suits a window set low, over a desk or in a room with limited head height. It is also, inevitably, at the height a three year old can reach. The difference between the two arrangements, and which suits which slope, is set out on our page comparing centre pivot and top hung units. For child safety the practical point is simply this: bar at the top is safer by geometry, handle at the bottom needs hardware.
The catch that holds a window shut against wind
The primary catch on a roof window is a two stage mechanism. Turning the handle draws the sash in against a perimeter gasket and holds it there under compression, and it is that compression rather than the catch itself that keeps water out.
On most ranges the same handle has an intermediate position that holds the sash locked but leaves a ventilation path open through a flap or a slot in the frame, so the room gets air with the window secure. That vent arrangement, the filters behind it and how it is set is covered on our page about ventilation flaps and filters. What matters here is that the intermediate position is a locked position, not a slightly open one, which is why it is safe to leave set overnight.
Barrel bolts and dedicated child locks
A child safety lock for a roof window is a small metal barrel that fixes to the frame and engages a keeper on the sash, holding the window shut independently of the handle. It is released by a key or by a deliberate two handed action.
These are made by each manufacturer for its own range and cost very little. Fitted to a low set window in a child’s bedroom, the lock means that turning the handle achieves nothing on its own. The pattern to avoid is a generic hardware store bolt screwed into a polyurethane frame at an angle that puts a load on the gasket. The frame has fixing points designed for this and the manufacturer’s part uses them.
Restrictors, and the travel they allow
A restrictor is different from a lock. It lets the window open, then stops it at a set point, typically somewhere around 100mm of clear gap depending on the range and the unit length.
That gap ventilates a room properly while being too small for a child to get through, and on many units the restrictor is released by a lever so an adult can open the window fully in a few seconds. The number that matters is the clear opening at the restricted position measured at the widest point of the gap, not the angle the sash has swung through. Ask for it in millimetres.
A lock stops the window opening; a restrictor lets it open a measured amount and no further, and a child’s bedroom usually wants both available.
Key operated handles, and where they are worth it
Some ranges offer a handle with a key barrel in it, so the window cannot be opened without the key. It is a straightforward upgrade at order and it is normally cheaper than adding a separate lock later.
The place it earns its keep is a low set window in a room a young child uses unsupervised, or a window at the top of a stair where the floor beyond the opening drops away. The place it causes trouble is a window doing double duty as an escape opening, where a key in a drawer at three in the morning is the wrong answer. If the unit is an escape window, the key stays in the lock or in a fixed holder beside it.
Guarding, glazing height and what Part K asks
Part K of the Building Regulations deals with protection from falling, and it engages where glazing sits low enough that a person could fall against it. The threshold that comes up is 800mm above the finished floor.
Glass below that line in a position where somebody could fall wants to be laminated, so that it holds together on the interlayer under impact rather than releasing. Where the floor does not continue beyond the window, at a stairwell edge or a mezzanine, that is a guarding question rather than a glass question and it is designed as part of the opening. Notification under Building Regulations is handled as part of the job, so the assessment happens whether or not anybody raises it.
A pivoting sash, and the space it sweeps through
A centre pivot sash rotates about a point roughly midway up the frame, which means as the bottom half swings out, the top half swings into the room. On a 1400mm unit the inner edge travels a surprising distance towards you.
Two consequences follow. Furniture placed hard under the window, a wardrobe, a shelf or a headboard, can foul the sash before it reaches the open position. And a child standing at the window while somebody opens it is in the arc of a moving glazed panel. Neither is dangerous with the arc known, and marking it on the wall at survey means the joinery and the bed both land clear of it.
The cleaning catch, and how the sash is held reversed
Centre pivot units rotate a full 180 degrees so the outer face can be cleaned from inside. Held in that position, the sash is retained by a barrel bolt that drops into a keeper on the frame.
That bolt is a safety component and it wants checking before every clean. It holds the weight of a rotated glazed sash with somebody’s hands on the outer pane, and a bolt that has worked loose in its fixing is the failure that matters on an otherwise trouble free window. It is one screwdriver and thirty seconds. In a household with children, the reversed position is also the one where the opening below the sash is at its largest, so the room is cleared before the sash is turned.
What a child can climb to reach the window
A cill height of 900mm is above a toddler and comfortably within reach of a five year old standing on a bed. The window is not the variable; the furniture is.
The arrangement that repeats in loft bedrooms is a bed pushed against the knee wall directly under the roof window, which is often the only place a bed fits. That puts a mattress surface at 500mm to 600mm right below the opening and turns a 900mm cill into an effective 350mm one. Where the layout cannot change, that is the window that gets the lock and the restrictor, and it is worth saying so at survey rather than discovering it at handover.
Handle materials, and what survives a bathroom
Handles and catches are normally aluminium or a zinc alloy with a lacquered or anodised finish, with stainless components in the hinge assemblies. In a dry bedroom the finish is irrelevant and any of them will outlast the glazing.
In a loft shower room the environment is harsher: warm chloride laden vapour twice a day, condensing on cold metal. There, the finish matters, and it is worth asking what the hinge and catch components are made from rather than assuming. This is the same reasoning that puts a polyurethane frame rather than a lacquered timber one in a bathroom, and the two decisions are made together.
Escape openings and child locks, and the tension between them
A window that is a designated escape route has to be openable quickly by an adult in the dark, and a window in a child’s bedroom has to be difficult for a child to open. Those two requirements pull in opposite directions and the resolution is a matter of choosing hardware that an adult can release in one motion.
A lever released restrictor satisfies both. A key operated lock with the key kept elsewhere in the house does not. Where the unit is serving as an escape opening the sizes and heights involved are covered on our page about escape openings, and the hardware is specified after that question is answered rather than before.
Motorised operation, and the control that sits out of reach
A motorised roof window changes the child safety question rather than removing it. The sash is no longer opened by a handle at all, so the control is a wall switch, a handset or an app, and any of those can be placed or restricted where a child cannot use it.
Wall switches go at adult height, handsets go in a drawer, and app control can be limited by device. Manual override remains available for a power cut, usually by a pole or by disengaging the chain, and it is worth knowing where that facility is before it is needed. The wiring and control options are covered on our electric rooflight page.
Closing force, obstacle detection and rain sensors
A chain actuator closing a roof window applies a real force through a small gap, and the sensible question about a motorised unit in a child’s room is what happens if something is in the way.
Current actuators monitor motor current and stop or reverse when resistance rises above the expected profile, which is the same principle a car window uses. Ask for confirmation that the unit has that behaviour rather than assuming it. A rain sensor introduces the same issue from a different direction: the window can close without anybody touching a control, on a schedule nobody chose, which is exactly why the obstacle behaviour matters.
Adjusting a catch that has gone slack
Over years of use a sash can start to feel loose at the closed position, or the handle can need more travel than it did. Almost always the fix is adjustment rather than anything more.
Most ranges have adjustable keepers on the frame, held by a screw in a slotted plate, which move the catch a millimetre or two closer so the gasket compresses properly again. Hinges are similarly adjustable for the sash sitting square in the frame. It is fifteen minutes of work and the manufacturer publishes the procedure. A window that is not compressing its gasket is a window that will let weather in eventually, so it is worth attending to when it is noticed.
Older units in Essex houses, and the ironmongery on them
Roof windows fitted across Essex in the eighties and nineties are still in plenty of slopes, and the hardware on them predates most current child safety options. Handles are often a simple single stage catch with no vent position and no provision for a lock.
Where a family has moved into a house with those units in a child’s bedroom, the useful assessment is whether the existing frame can take a manufacturer’s lock at all, and whether the glazing at low level is laminated, which on units of that age it usually is not. Both are answered by looking at the frame data plate, and both often point towards replacing the unit, which brings current hardware, current glazing and a warmer room in the same day’s work.
What to specify at order for a child’s room
Five lines on the order settle it. The handle arrangement, top bar or bottom handle. A laminated inner pane where the cill is below 800mm. A manufacturer’s child lock or key handle for the range. A restrictor with the clear opening stated in millimetres. And whether the unit is also serving as an escape opening, because that determines which of the others can be used.
All five are decided at survey, and none of them can be added to a unit that has already been made without compromise. This is the part of a VELUX installation that gets skipped most often on a price led quote, and it is the part a parent notices first.
Keep reading
More on velux window installation
Roof window escape openings and the rules
Read the guide →Roof window blinds and when to specify them
Read the guide →Roof window flashing kits by roof covering
Read the guide →Roof window sizes and how they are coded
Read the guide →Roof window ventilation flaps and filters
Read the guide →
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