The quiet spec: the written note that comes with every quote

The quiet spec is a short written note that arrives with every quote. It records what we heard at the survey, the glazing build we propose because of it, and how the seals and upstand are finished.

A rooflight is chosen, most of the time, by size, price and look. Noise rarely comes into it until the first wet night or the first early flight. By then the glass is in and the roof is closed. The quiet spec moves that conversation to the start. It puts the noise on paper before anything is ordered, so you can see why a particular pane has been proposed and decide whether you want it.

It is a specification, not a performance claim. It names the parts: which glass, how thick, how the units are sealed, how the upstand is built and lined. It does not quote decibel figures, because what matters to you is what goes into your roof, and a written list of parts is something you can check against the delivery and against the finished job.

The note sits beside the written quote. You can read the price and the reasoning together, and you can ask us to change either.

The survey is partly a listening visit. We stand in the room under the opening, and then outside on the roof or at the edge of it, and we note what reaches us.

Crawley gives us plenty to listen for, which is why the practice began here. Gatwick sits inside the borough, and departures and arrivals pass over the town and the villages around it. A loft bedroom under a rooflight is the room that hears the sky most clearly, because the roof is the thinnest part of the house and the glass faces straight up. We note which way the aircraft pass, how low, and whether the room is one you use early or late.

Away from the airport the noise changes. The A23 and the M23 run through and beside the town, the M25 lies to the north, and the Brighton main line cuts through Three Bridges and on towards the south coast. Houses near a road or a railway take a steady low sound that a thin unit can carry inside like a drum skin. In the towns around us, such as Horsham, Reigate and Haywards Heath, the source is as likely to be a busy road, a school or a station.

Then there is rain, which affects every flat roof and every lantern wherever it is. Rain on glass makes a sharp, broad sound, and a kitchen lantern over a dining table can be surprisingly loud in a downpour. We note the pitch, the size of the panes and the surface under the glass.

Finally we listen to the room itself. Hard floors, bare walls and a high ceiling all make a rooflight seem louder, and a room with soft furnishings seems quieter. The spec records these so the choice fits the room as it is used.

The build is the stack of glass and gaps inside the frame. It is the main lever we have on how much noise comes through, and the spec names every layer.

A typical rooflight unit has an outer pane, a sealed gap and an inner pane. On a quieter build the inner pane is laminated: two sheets of glass bonded with a clear interlayer. The interlayer does a simple job. It stops the pane ringing like a struck plate, which is how thin glass passes sound through. Laminated glass is also a safety glass, so it has a second reason to be there.

The outer pane is often thicker than the inner one, or different in thickness. That is deliberate. Two panes of the same thickness tend to vibrate at the same frequency and pass sound more easily, so unequal panes cope better. The width of the gap between them matters too, and it is chosen together with the thermal build, because a wider gap helps sound but the unit still has to meet current Building Regulations for heat loss.

Coatings and gas fills belong to the thermal side, and they are written into the spec as well, so you can see the whole unit in one place. The energy efficient rooflights page explains how that side works. Some rooms need solar-control glass as well, such as a south-facing loft that gets hot, and the spec says so.

For a walk-on unit or a large lantern, the build also has to carry load and span, so the thickness is set by the structure first and by sound second. The spec explains how those two needs were balanced. See walk-on rooflight installation and roof lantern installation for the structural side.

Glass can be excellent and a rooflight can still be loud, because sound finds the gaps. The frame, the seals and the upstand decide how well the glass is kept from being bypassed.

Seals first. A tired or thin seal lets air through, and air carries sound with it. The spec names the seal type at the opening sash and the gasket around a fixed pane, and it says what is used where the frame meets the upstand. A sealed unit with a good continuous gasket is a different thing to a frame that was squeezed shut over an old strip.

Then the frame. A thin, hollow frame can hum when the wind is up, and a stiff frame with a thermal break sits still. On a flat roof, the frame sits on an upstand or kerb, and this is the piece people forget. A hollow, thin upstand carries rain noise and traffic noise into the room like a sounding board. A solid, insulated upstand with the membrane dressed up and over it is quieter, and it is warmer as well.

Inside the room, the lining around the opening matters. The spec notes how the reveal or splay is finished, with insulation packed behind the plasterboard and a sealed joint at the frame, so there is no draughty crack for sound to use. The flat roof rooflight installation page shows how that upstand is built, and the roof window installation page shows the equivalent for pitched roofs.

Every spec follows the same order, so you can compare one with the next. A typical note uses these headings.

The reasoning line is the part that matters most. It connects what we heard to what we propose. A loft bedroom on a Gatwick departure path might carry a laminated inner pane and an unequal outer pane. A kitchen lantern might carry a thicker outer pane and a solid upstand because rain is the concern. A small hallway window on a quiet close might carry a plain, good-quality unit and a short note saying nothing more is needed.

A promise made on the doorstep is hard to hold anyone to. A written specification is easy to hold to, and that is the reason we write it.

It protects you. You can check the delivery against the note, check the installed unit against the note, and show the note to a builder, a surveyor or a future buyer. It protects the job too. When the glass, the seals and the upstand are named in advance, nobody on the day is tempted to swap in something cheaper.

It also keeps us honest. If we heard aircraft and proposed ordinary glass, the note would look odd, and you would ask why. Writing the reasoning down forces the reasoning to exist.

And it makes quotes comparable. If another installer gives you a price without naming the glass, you can ask them to write the build down beside ours. The costs page explains how to read two quotes side by side, and how glazing build feeds into the price.

The quiet spec is one page of a wider written record. It works alongside the quote, the Building Control notification and the guarantee.

The quote gives the scope and the price. The spec gives the reasoning about noise and the glazing build. Where the work is notifiable, we handle the Building Control notification, and the work is installed to current Building Regulations, so the thermal and safety side of the glass is already part of the plan. The 10-year workmanship guarantee then covers the installation of what the spec describes.

If you change your mind about a room, the spec changes with you. Move the bedroom, add a second opening, choose a different product: we revise the note and the quote together, so nothing is left behind from the earlier plan.

Ask for a quote, and the spec comes with it. There is no separate charge for the note and no obligation to go ahead.

Tell us about the room, the roof and what bothers you about the current unit, or what you fear in a new one. We arrange a survey across Crawley and the 30 miles around it, listen, measure and write. The quote form on this page gets that started, the contact page lists WhatsApp and email, and about Clear Skylights explains why the quiet comes first in the way we work.

Does every rooflight need an acoustic build?

No. Where the survey finds a quiet room, the spec says a standard good-quality unit is enough. The acoustic build is proposed where the room hears something worth reducing.

Can I see the spec before I accept the quote?

Yes, it comes with the quote, so you read both before deciding. You can ask for changes to either.

Will it include a decibel figure?

No. It describes the parts of the build by name and thickness, and the method used for seals and upstand. That is what you can verify on site.

Does it apply to replacement jobs?

Yes. A replacement is the best time to improve the glass, so the note records what the old unit let through and what the new build is chosen to do about it. The page on misted and failed rooflight replacement covers that route.