Glossary of Terms

Understanding the jargon

There are many terms related to loft conversions that you may not be familiar with. On this page we have provided a glossary of the common terms with an easy to understand explanation. We want to help you understand and cut through the jargon so you will feel comfortable when speaking with a builder.


If the space and headroom within your loft is limited, it may make sense to opt for a dormer style conversion.A dormer is where the roof is extended to give more internal room to the conversion.

Loft Conversion

A Loft Conversion involves building an additional room within the loft space of your home. If you are looking to increase the living space in your home a loft conversion is a cost effective way to acheive it.


A mansard conversion is where the roof is converted to have two pitches on each side.


RSJ stands for Rolled Steel Joist, which is an 'I' beam made from rolled steel. When used in loft conversions they are typically used to support the floor of the loft conversion and the ridge of the roof. Sometime RSJs are incorrectly referred to as a reinforced steel joist.

Shell Conversion

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


Velux double glazed roof windows are considered to be the best available. With a large range of styles and sizes there are plently to choose from for your loft.

Is there a term missing form our glossary?

Have you spoken with a builder recently and felt confused due to the jargon? Thats where or glossary aims to help you understand what all the terms mean. However, there may be some missing from our list, if you know of one then drop us a line, we will be pleased to hear from you.