Room in Roof - Measuring and Recording Insulation
Understanding the simplified and detailed method
Dominic Bowkett
Last Update 2 hours ago

This article helps define a room in the roof, and how the insulation levels should be measured and recorded.
Relevant Conventions
Convention 2.06 and also Appendix 2. Illustrations of roof rooms
What is a Room in the Roof?
A room in the roof could be a loft conversion, or could also be a property with a floor originally built within the roof space. Here's some help on how to determine this.
Convention 2.06 states "For a roof room to be classed as such and not a separate storey, there must be no common wall, or the height of the common wall must be equal to or less than 1.8 m, for 50% or more of the common
wall (excluding gable ends or party walls), otherwise it is a separate storey. The common wall is a vertical continuation of the external wall of the storey below."
To summarise this convention...
- Gable ends and party walls are not common walls for the purposes of determining a room in the roof.
- The common wall (of which there may be more than one) must be 1.8m or less (for more than 50% of it's length) to be classed as a room in the roof.
- The common wall can be determined by looking at the property from the outside to determine if the wall continues into the story above.
- A measurement can be taken inside to determine to height of any continuation of the common wall.
Remember to include when accessed via a permanent fixed staircase such that one is able to walk downwards facing forwards. If this is present, even if the room is not heated, it is still included as a habitable room.

Types of Rooms in the Roof
There are 2 types of room in the roof assessors need to be familiar with.
Type 1: A room that is fully within the roof.
In the diagram below, the common wall is seen in blue. Stud walls are in green. This shows a room that is fully within the roof.
The 1.8 m rule does NOT apply to RR Type 1 - as it is fully within the roof.

In the diagram below, no stud walls are present and we can see that the common wall in blue is 1.8m or less in height. Therefore this is a room that is not fully within the roof, but is recorded as a Type 2 room in roof by assessors.

The Simplified or Detailed Method?
Once we have determined the type of room in roof, we then have to record relevant information regarding the room, using either the simplified or detailed method.
The Simplified Method
Where a room in roof is “As Built” and there is no insulation accessible, the simplified method is used.
What is recorded depends upon the room in roof being Type 1 or Type 2.
Type 1: A room that is fully within the roof.
- Record the length of the gables walls at their widest part.
- Record the type of gable wall.
- The measurements of the length (the widest part) and
height (to the highest point) of the gable(s) and common wall(s) will be required. - The type of gable walls.
There is no explicit allowance for dormer windows except to include in the floor area of the roof rooms.
Gable Wall Types:
For each roof room, you must record the gable wall type. This can be one of the following:
- Exposed: Open to external air.
- Party Wall: Next to a heated space — for example, a neighbouring property where the space is an original roof room, a verified loft conversion, or where dormers can be seen from the outside.
- Sheltered Wall: Next to an unheated space — for example, a neighbouring property’s loft space.
- Connected: Next to another part of the same dwelling.
If a roof room does not have any exposed gable walls (such as in a hipped roof), assume the stud wall above the gable walls of the lower floor is the exposed gable wall, and measure it in line with the guidance above (Convention 2.06).
The Detailed Method
If any element of the roof room (ceiling/slope/stud/gable/common wall) have known insulation levels (see convention 3.07) the detailed assessment method must be used, and all elements must be
measured.

The first step to accurately inputting detailed information is to:
Measure all accessible areas of the roof room and record the height and length of the following where applicable, including the insulation levels:
- Gable Wall 1
- Gable Wall 2
- Stud Wall 1
- Stud Wall 2
- Slope 1
- Slope 2
- Flat Ceiling 1
- Flat Ceiling 2
Gables walls
When referring to the height and length see the example below for gable wall measurements.

Slopes
When referring to the height and length see the example below for sloping ceiling measurements.

Flat Ceiling
Please see below for the length and the height.

Stud Walls
Please see below for stud wall measurements.

Evidence should be collected to confirm the presence of insulation levels in all areas where is is recorded. Therefore, photos of stud wall, flat ceiling or slope insulation with measurements should be taken.
Where the detailed assessment method is used and the floor area of the parts of the dormer windows protruding beyond the roof-line is less than 20% of the floor area of the roof room, measure the elements of the roof room as if the dormers were not there. Otherwise total the vertical elements of all dormers in that building part and enter as stud wall and the flat ceiling elements as flat ceiling (Convention 2.06).
Conclusion
So hopefully now you'll be able to understand when to record as a Type 1 or Type 2 Room in the Roof, and whether to use the simplified or detailed method, and what measurements are required.