The short answer
A roof window can be noisy in rain, but it does not have to be. A pitched pane sheds water quickly, so the sound is a patter rather than a drum. What you hear depends on the glass build, the seals, and how much soft material sits between the pane and the bed. A laminated inner pane with a thicker outer one keeps a loft room calm.
What rain does to a tilted pane
Rain falling on a sloped window behaves differently from rain landing on a flat one. The slope is the reason a roof window is usually the gentler of the two.
On a pitched roof window the water does not sit. It strikes the glass, runs down the surface and leaves over the lower edge. A flat pane holds a shallow film that a heavy shower keeps hitting, which is why flat glass can sound like a drum. On a slope each drop lands at an angle and shares its energy with the film running past it, so the impact is softer. The steeper the pitch, the quicker the water clears, and the less of it the glass has to carry.
That said, a loft bedroom is the room that hears the weather most. It sits directly under the roof covering, with a few millimetres of glass and a short stretch of insulation between you and the sky. There is no attic above, no ceiling void and no second floor to soften it. A window that would be unremarkable in a hallway can be the loudest thing in a loft at two in the morning.
The slope of the roof matters here too, and our page on roof pitch and roof windows explains how angle affects run-off as well as light.
Where the sound actually comes from
People blame the glass, and the glass is the biggest part. But three other things can add a tap, a buzz or a hollow note.
- The pane itself. A thin pane flexes when a drop hits it, and the flex is what you hear. Two panes of the same thickness flex together, so they add to each other.
- The sash and seals. A sash that does not sit firmly against its gasket can tick in wind and rain. Tired seals, or a sash closed lightly on a warped frame, let a sharp edge of sound through that the glass itself would have muffled.
- The flashing and the covering around the frame. Metal flashing conducts the impact of rain into the frame. A loose or thin apron rattles. A well-fixed one, bedded on proper battens, stays still.
Our page on flashings for tiles and slates sets out how the frame is tied into the roof covering, which is also how it stays quiet.
The roof covering matters as well. Rain on clay tile or natural slate is a soft, dispersed sound, because the material is dense and the water runs off in a broad sheet. Rain on a thin profiled metal sheet is sharper. Over a tiled or slated roof the surround is calm, so the glass is what stands out.
The builds we specify for a quiet loft
The glazing build is the decision. A few well-chosen changes do more than any accessory, and each one is written into the quote.
The standard double-glazed roof window has an outer pane, a sealed cavity and an inner pane. The first change is to make the inner pane laminated. Two sheets of glass are bonded with a plastic interlayer that damps vibration, so the patter reaches the room with less edge. The second is to give the outer pane a different thickness from the inner one, so that the two do not ring together. The third is the seal, which has to be continuous and to close with the sash tight to the frame.
| Build | What the rain does | Suits |
|---|---|---|
| Plain double unit, equal panes | Patter with a crisp edge | Landing or store |
| Laminated inner pane | Softer, rounder patter | Loft bedroom |
| Laminated inner, thicker outer | Low, even hush | Nursery or office |
| Triple unit | Varies with pane mix | Where warmth leads |
Triple glazing is chosen for warmth first. It adds weight, and unless the panes are mixed in thickness it does not cure rain on its own. Our guide to acoustic glazing options for loft roof windows sets the combinations out side by side, and our answer on laminated glass in a loft bedroom covers the safety benefit overhead.
What you can do inside the room
Softness inside reduces how lively the sound is. The window is one half of the story and the room is the other.
A loft bedroom with a bare floor, plain plaster slopes and a bed against the window wall gives rain a lot of hard surface to bounce from. A rug, curtains on the landing side, and a well-lined reveal all take some of the sparkle out of the patter. A fabric blind fitted to the window frame sits close to the glass and absorbs a little of the tone, though it does not stop the pane from moving. Our page on blinds for roof windows compares the types.
The lining around the frame has a part to play, too. A solid, well-fitted lining gives the sound less room to echo in the reveal, and it is worth reading our page on roof window linings and making good the reveal if the room is being redecorated.
We listen for these things at the survey. The build we propose for the room, with the panes, the interlayer and the seals named, goes into the quiet spec that comes with every quote.
Rain noise in a roof window: your other questions
Are roof windows louder than flat rooflights in a downpour?
Generally the reverse, since a slope clears the water faster. A flat unit with thin glass can drum, and a pitched unit with a matching build is gentler. The comparison depends on the glass, so read our page on flat roof rooflight installation for the flat side.
Does opening the window change the sound?
Yes. Open, the room hears the rain directly, and water can reach the sill. Our answer on leaving a roof window open in the rain explains how far you can go.
Will a noisy old window be quieter if it is replaced?
If the noise comes from thin panes or tired seals, yes. A new unit with a laminated inner pane and a fresh gasket changes the sound more than anything done from inside. The wider service is set out under misted and failed rooflight replacement.
Is hail louder than rain?
On any roof glazing, yes. A laminated inner pane also stays together if the outer pane is struck hard, which is an extra reason to choose it.
If you would like a loft that stays hushed in a downpour, get a quote and we will write the glass build into your spec. The full service is on our roof window installation page.