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Some Useful Terms Used In Loft Conversionsloft-conversion-rear-dormerLoft Conversions – A Glossary

Updated: Jun 15, 2021

Breaking down some of the jargon used in converting a loft!


A conversion with an extension to the roof is called a “Dormer”.

Rear Dormer

A Rear Dormer is the most common type of loft conversion and will create maximum floor space and height. It is often possible to construct a rear dormer without need for planning permission.


Hip-to-Gable will involve changing the sloping side of your property. This may often be a better alternative to a side dormer and in many cases will create more space.

Side Dormer

A Semi-detached house with ‘hip-ended’ sloping side roofs will invariably need a side dormer. This will give sufficient head room, we will design the best choice of dormer to suit your home and your needs.

Mansard Roofs

A Mansford roof is a dormer conversion with a sloping front of 70° which can take either roof lights in the slope of the new roof or new vertical windows. This type of conversion is usually constructed where certain planning permission is required or your property falls into a conservation area.

Velux Conversions

With a Velux Conversions the roof line is unaltered and a room is created in your existing loft space. This type of loft conversion is very cost effective and is often used if planning permission is an issue. Velux™ windows are available in a huge range of designs and styles, for flat, sloping and pitched roofs, in wood and polyurethane frames, with various shutter designs, rollers and glazing, and with electric controls.


RSJ stands for Rolled Steel Joist. It is a metal beam whose cross section resembles the letter I. They are used in loft conversions to support and strengthen loft floors.


Rafters are the main sloping roof timbers which form the roof structure of a building.


A batten is a small strip of sawn timber that is fixed across the rafters on a roof to provide support for tiles or slates.


Binders are thin strips of timber nailed across the top of the ceiling rafters in lofts to strengthen the structure.

Shell Conversion or First Fix Conversion

A shell conversion is a part build where a qualified builder will undertake all of the technical and difficult work such as installing steel work, stairs and structural elements of the job. The finishing work such as installing doors, skirting boards and decorating can be completed by a competent amateur and can reduce the overall cost of the loft conversion.

We hope that this explains some of the jargon but if you want a full explanation of what is involved in converting your North London loft, pick up the phone and call Sunlight Lofts!

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