The short answer
Most conservation rooflights do have a glazing bar, and the classic pattern is a single slim bar running down the centre of the glass from top to bottom. It is a design feature taken from the cast iron and steel rooflights of Victorian and Georgian buildings, and it is usually optional: many makers also supply the same slim frame with one clear pane and no bar at all. Which suits your roof depends on the size of the opening and on how the old rooflight, or the buildings around you, were detailed.
Why the bar is there in the first place
Old roof glazing was made of small panes because large sheets of glass were expensive, fragile and hard to get up a roof. A thin iron frame held a row of narrow panes, and the bars between them were the structure. A conservation rooflight keeps that look. The bar splits the glass into two halves, so the opening reads as a fine, divided window and not as one large sheet of modern glass.
On a modern conservation rooflight the bar no longer has to hold the glass up in the old sense, but it still does a job. In a wider opening it gives the sealed units a firm line to sit against, and it breaks up a big reflective surface on a roof that is seen from the street or the garden. That second reason is the one planning officers tend to care about.
Where the bar runs and what it looks like
On a pitched roof the bar normally runs in line with the slope, from ridge towards eaves, so it sits in line with the rafters and the courses of slate or tile on either side. Run it across the slope instead and it looks wrong against the rows of slates. A rooflight with the bar in the centre also looks balanced, in the way a sash window with a glazing bar does.
The bar itself is slim, a thin upright of steel or aluminium that shows on the outside as a fine line and on the inside as a narrow rib in the lining. Some are built into the frame. Others are a surface-applied strip fixed over a continuous pane to give the appearance without the divided glass. The difference matters if you have sealed double glazed units: a built-in bar means two smaller units, while a stuck-on strip leaves one larger unit and a bar you can see but cannot feel.
Ask the maker which of the two you are looking at. Both are accepted conservation-style products, but they are not the same thing, and a quote ought to say which one is allowed for.
When to leave the bar out
A small rooflight does not need one. On a narrow opening, say one sized to sit between two rafters in a cottage roof, a central bar leaves two panes that are each a few inches wide, and the frame starts to dominate the glass. A single clear pane looks calmer and lets in a little more daylight.
The bar can also be left out when:
- the rooflight is on a rear slope that is not seen from any public place;
- the building is modern or an extension, and a heritage look is not what the roof wants;
- the opening is an opening vent, where a bar in the moving sash can complicate the hinges and the seals.
It is the other way round on a long, wide opening. If the glass is much larger than the panes in the old windows around it, a bar helps to bring it back in scale with the rest of the building.
Glazing bars on a listed building or in a conservation area
Where the house is listed, any rooflight needs listed building consent, and the conservation officer will look at the bar closely. They may ask for one, ask for it to match an existing pattern on the building, or prefer none on a modest outbuilding. There is no single rule, so decide with the officer, not around them. Our guide to conservation rooflights for listed buildings covers how the consent process usually runs.
In a conservation area, a rooflight on a house is normally permitted development unless an Article 4 direction takes that right away, and the detail of the bar is a matter of taste more than law. Even so, a visible rooflight with a fine central bar tends to sit better in a conservation area than a plain sheet of glass, and it tends to draw fewer questions. If you are not sure whether your road is covered by an Article 4 direction, a quick call to the council's planning team before ordering settles it.
What the bar means for the room below
The bar shows from inside too. Looking up, you see a fine line down the middle of the opening, and the way the lining is formed around it affects how neat that looks. If the lining is splayed, the bar should line up with the centre of the opening, and the plaster either side should come to a clean edge against the frame on both sides.
The bar also casts a thin, slow-moving shadow across the lining through the day. Most people like it, but it is worth knowing before you choose, because a bar that looks charming on a sample can feel busier on a small ceiling.
Whether the unit has a bar is written down in our quote paperwork, together with where the bar sits in relation to the ceiling opening and how the lining meets the frame either side of it.
Choosing between a bar and no bar
A few questions settle it quickly. Is the rooflight visible from the road or a neighbour? Is the roof slate or old clay tile, where fine detailing is expected? Is the rooflight wider than the windows around it? If the answers are yes, a central bar is usually the better choice. If the opening is small, hidden or on a newer part of the house, a clear pane is a fair option.
Size and bar are linked, so it is worth reading about what size conservation rooflight suits a cottage alongside this. If you want to know what qualifies a unit as conservation-style in the first place, see what makes a rooflight a conservation rooflight. And for the whole subject, from fitting to finishing, start with our conservation rooflights page.
When you want a recommendation for your own roof, ask for a quote. We will look at the slope, the rafters and the ceiling below, then tell you whether a bar suits the opening and write the answer into the schedule.