Does a conservation rooflight need a glazing bar?

What the glazing bar is

A glazing bar on a conservation rooflight is a slim vertical strip, running down the centre of the glass from top to bottom. It divides the opening into two panes. On the modern unit it can be a purely visual feature, as the glass is held by a frame that does not need the bar to carry it.

The design copies the historic cast-iron rooflight, the kind found in Victorian terraces, outbuildings, warehouses and cottages. Those units were made in small panes and had a bar because of how glass was made and carried at the time. The modern version keeps that look while using current glass and seals.

Many of these units are described as conservation rooflights for this reason, and the bar is one of the first things people notice from the street, which is why councils pay attention to it: the bar, the slim frame and the low profile together resemble the original pattern.

When a bar is asked for

A bar is asked for by the planning authority, not by the manufacturer. In a conservation area, on a listed building or inside a National Park, officers may say the new rooflight should look like a traditional one, and a central bar is a common way of doing that.

A planning condition attached to an earlier permission for the property can say the same. An Article 4 direction, where one exists, removes some permitted development rights, so the council then decides the style. We never assume one applies to your street; the way to find out is to ask the council or look at the property's planning history on its website.

Our guides to rooflights in conservation areas and rooflights in the New Forest and South Downs National Parks explain how to find which authority covers your address, and what it is likely to look at.

Fitted with a bar or without

If the council does not require a bar, the choice is yours. A bar suits a roof in period character, particularly slate roofs on Victorian or older houses. A barless rooflight gives a clearer view and a more contemporary look, and works well on a roof where the glass will be seen only from above.

The bar has a small effect on how much light comes through, because it takes up a little of the width. In a slim frame the difference is modest. The bar also splits the view when you look up and out, which some people like and others do not.

Where a listed building is involved, a bar is more likely to be part of what is agreed, so it is better to decide with the conservation officer before ordering.

How the choice affects the unit and the order

A rooflight with a bar and one without are different products from the maker, so the choice is made when we place the order rather than on the day. A unit made with a bar cannot have it removed afterwards, and one without cannot be given one.

Opening units are available from several makers. The way a bar sits with the opening mechanism varies, so ask for a drawing if your unit is to open. The frame detail, the finish and the glazing specification are all named in our written quote.

The price is set by the whole specification, not by the bar alone. The conservation rooflight cost page explains what moves it.

Glass, frames and the energy rules

The bar is part of the frame, so the glazing in each pane is sealed double glazed units, with triple available from some makers. Our page on double glazing in conservation rooflights covers this.

Whatever the pattern, a rooflight put into an existing home must meet the Part L energy limits, and the maker's data for the chosen size shows how it performs.

See the Building Regulations guide for the detail.

How we help you decide

At the survey, we look at the roof, the house and the street and report on the position. Where a bar is likely to be wanted, we say so and quote the unit with it. Where nothing is required, we show you both versions.

The quote states which rooflight is being supplied, whether it has a bar, the glass, the maker's delivery time and what the builder must have ready. Opening dimensions reach the builder or architect on paper before roof construction starts.

More on the range is on the conservation rooflights hub, and on whether this type suits your roof in conservation rooflight or standard roof window.

Related questions

Does the bar split the view from the room?

It runs down the middle of the glass, so when you look straight up there is a thin vertical line across the sky. Most people stop noticing it quickly, and it matters less in a loft or stairwell where the rooflight is mostly a source of daylight.

Can I add a bar to a rooflight I already have?

A bar is built into the frame at the factory, so an existing unit cannot be given one. If a council asks for the pattern, the usual answer is to replace the whole rooflight with one that has it, which we can quote after a survey.