Rooflight Loft Conversions in Cambridge

A rooflight conversion — often called a Velux conversion after the best-known make of window — is the cheapest, quickest and least disruptive way to turn a loft into a room. It is also the one option that depends entirely on what you already have, because it adds no volume to the roof. If the head height is there, it is usually the right answer. If it is not, no amount of money spent on this type will create it.

Our loft conversion costs guide carries published Cambridgeshire ranges by type and puts the difference in cost between this and a dormer in context.

Head height decides everything

Because the roof shape does not change, the room you get is the space that is already up there, minus what the build takes out of it. Two things eat into the height you measure standing in the loft today.

The first is the new floor. Existing ceiling joists were sized to hold up a ceiling, not people and furniture, so a new floor structure goes in — and it usually sits above the existing joists, raising the floor by some amount.

The second is insulation. The rafters have to be insulated to current standards, and where there is not enough depth between them, insulation goes under them too, which drops the ceiling. The honest figure is the height after both, not before. Anyone quoting off a tape measure held up in an empty loft is quoting off the wrong number.

What the work actually is

The structure is the main job even though nothing changes outside. A new floor is designed by an engineer and inspected by Building Control. Where rafters are cut to take a rooflight, they are trimmed and the load carried around the opening rather than simply cut through.

Then it is insulation, plasterboard, the stair, electrics, heating and finishes — and, in most cases, fire safety work on the floors below, because the loft becomes part of a protected escape route. That last item is a Building Regulations requirement rather than an upsell, and it is the thing homeowners are least expecting. Our Building Regulations guide explains how it runs alongside the build.

The rooflights themselves

Where they go matters more than how many there are. Set them low enough in the slope and you get a view out while seated; set them high and you get daylight but a room that feels like a corridor with a skylight. At least one usually has to be an escape window, which sets a minimum size and a maximum sill height, so that one is not a free choice.

Rooflights that sit flush in the plane of the roof look considerably better from the street than ones that stand proud, and on a visible elevation that difference is worth having.

The stair problem is the same

People assume that because a rooflight conversion is the simple option, the staircase is simple too. It is not. The stair needs head height over its whole length, it has to land where it does not ruin the floor below, and on a shallow roof the head height at the top of the stair is often the very thing that is in short supply. On more than one survey the stair, not the room, is what rules this option out.

When it is the right answer, and when it is not

It is the right answer when the loft already has generous height across a decent width, when the budget is the constraint, when you want the work done with the least disruption, or when planning makes a dormer difficult — a rooflight conversion changes nothing visible in the roof line, so it is the least contentious option on a prominent elevation or in a conservation area.

It is the wrong answer when the height is marginal. Spending the money to end up with a room you can only stand up in down the middle is the most common regret in loft conversions, and it is entirely avoidable by measuring properly at the start. If the height is not there, the honest options are a dormer, or leaving the loft alone.

Common questions

Do I need planning permission?

Usually not. Rooflights that sit within the plane of the roof normally fall within permitted development, subject to conditions, and this is the least likely of the three types to need an application. Conservation areas and front elevations are the exceptions. See our permitted development guide.

Do Building Regulations still apply?

Yes, in full. Planning and Building Regulations are separate, and the fact that a job needs no planning application says nothing about the regulations. Structure, insulation, fire safety and the stair all have to comply and be inspected.

Can I do it without a proper staircase?

Not if you want it to be a habitable room. A loft reached by a ladder remains storage — it cannot be called or sold as a bedroom, and it will show up on a survey when you come to sell.

How much cheaper is it than a dormer?

Materially cheaper per square metre, because you are not building a structure outside. The loft costs guide sets out published rates for each type side by side.

How disruptive is it?

The least of the three. The roof is not opened up in the way it is for a dormer, so the house stays weathertight throughout, and most of the noise is the floor and the stair opening.

The other two types

If the height is not there, a dormer conversion creates it. If your roof is hipped, a hip-to-gable conversion gives the most room of the three. The loft conversions page covers how we run all three.

Send us the height at the ridge and the width of the loft and we will tell you honestly whether this is worth pursuing. We aim to respond to every enquiry within one working day with the most useful next step.