Should you replace all your skylights at once?

A single visit saves on access, keeps the glass consistent and lets one specification cover the whole house.

1. Access is shared. Getting safely onto a roof is a fixed part of the job. A ladder, a roof ladder or a scaffold tower has to go up once for the first unit and could serve four more without coming down. Where a tower or full scaffold is needed, putting it up a second time a year later repeats that effort. Our answer on scaffolding to replace a skylight explains when it is needed.
2. The units are the same age. Rooflights fitted in the same year, by the same builder, tend to reach the end of their working life in the same few years. If one has gone cloudy, the others are often not far behind. Our page on how long a rooflight lasts sets out what drives that.
3. The house should look and sound consistent. New glass beside old shows. Glass tint, frame finish and the bar pattern on a lantern all age, so one bright new unit among tired ones is easy to spot from the garden. Indoors, a mixed set means some rooms have a quieter build than others.

That last point is where the quiet spec helps. When every opening is surveyed in one go, the glazing build for each room can be chosen against the same listening notes, and the written spec covers the whole set in one document.

A single replacement is sensible when one rooflight has a clear problem and the rest are sound.

Think of a kitchen lantern with a cracked pane, a bathroom unit that mists while two others stay clear, or a roof window that has been damaged by a fall of branches. These are cases of one unit changing, not a whole age group going at once. Replacing the single unit answers the problem, and the others can wait until their own signs appear. Our list of signs a rooflight has failed helps you tell the difference between a one-off and a pattern.

A second reason to go singly is the budget. Spreading the work over two or three years is a legitimate plan so long as you accept the trade: a repeat visit, and glass that will not quite match for a while. We would rather say that plainly at the survey than promise an exact match we cannot give.

New and old panes rarely look the same, and the difference is easier to live with when you know what causes it.

Glazing specifications have moved on. A unit from twenty years ago is likely to have a plain clear pane with a basic spacer and no coating. A current unit normally carries a low-emissivity coating, a warm-edge spacer and gas fill, because Part L now asks for better thermal performance. Low-emissivity glass can look very slightly different in tone when viewed at an angle. Nothing is wrong with either. They are just from different eras.

A full replacement avoids the question, since every pane comes from the same specification. Where you stage the work, we can choose the next unit to sit as close as possible to the ones already in. Our pages on energy efficient rooflights and whether an old skylight is worth replacing cover what the newer build adds.

Doing several at once does not mean opening the whole roof at once. The work goes one opening at a time, so each is weathertight before the next is started.

The sequence is the same for each: the old unit is taken out, the upstand or kerb is checked and made sound, the new unit is fitted and the flashings are dressed, and the inside reveal is finished. Only then do we move on. If the weather turns, the openings already done are closed and the ones still waiting are untouched. Our answer on fitting a skylight in the rain explains how we handle the forecast, and the time for a single unit is covered under how long it takes to replace a skylight.

Because the job is an exchange of units in existing openings, it is often a matter of replacing glazing, and whether each one is notifiable is checked for that house. Where the work is notifiable we handle the Building Control notification, and the detail is in whether replacing a rooflight is notifiable.

Four quick checks tell you which way to lean.

• Are all the units from the same year and showing the same wear?
• Is the roof awkward enough that a second access is a real cost?
• Do you want every room to share one glazing build?
• Is one unit clearly in trouble while the rest are fine?

If the first three are a yes, doing the lot is usually the tidier route. If only the fourth is a yes, replace that one and review the rest later. Either way, the choice goes into a written quote, and the costs page explains what moves the price up or down.

Will doing them all at once be cheaper per unit?

Often it lowers the overhead, because access, set-up and travel are shared. The glazing itself costs what it costs. We set out the lines in the quote so you can see where the saving falls.

Can I mix types, for example a lantern and two roof windows?

Yes. Each type has its own detail, so a mixed job is surveyed unit by unit. Our roof window installation page covers the pitched-roof units.

Do I need to be at home throughout?

Someone needs to let us in and to see the rooms at the end. The rooms below each opening are cleared and dust sheeted first, and we make good as we finish each one.

What if I want some units bigger?

Enlarging an opening is a separate piece of structural work, described in putting a bigger rooflight in the same opening. It can be done in the same visit as the other replacements, and it starts with a survey. You can get a quote for the whole set, or return to the skylight and rooflight installation page.