 Is the internal lining of an external wall a part of the wall? So if a wall was a part of the external wall, is the plasterboard on the inside of that wall a part of the wall? Why would anyone ask this question? Well, this question comes up when someone is applying C19A1 to type A or type A buildings. C19A requires a number of elements in type A or type A buildings to be non-combustible and the first of these is one. Extender walls and common walls, including all components incorporated in them, including the facade covering, framing and insulation. There are some defined terms in there which are worth remembering. The first one to look at is non-combustible. As you can see here, we talk about a material or a form of construction. When you have a material, it must be a material that can withstand an AS 1530.1 test. When it's a form of construction, it has to be made up of materials that can withstand that made up of materials which are non-combustible. The next definitions are things that C19A1 requires to be non-combustible, external walls and common walls. The external wall is the out wall of the building, which isn't a common wall. And a common wall is a building which is common to adjoining, is a wall which is common to adjoining buildings. And common walls and external walls need to be non-combustible as well. So is the internal lining of an external wall or even the internal lining of a common wall a part of that wall? Well, we say yes. If you want that in writing, here it is, the fire performance of external walls, including advisory note. Part 1.2 of that document talks about what an external wall is and specifically points out that the internal lining of an external wall is considered a part of that wall. This advisory note is available from our website, abcb.gov.au. This answer may seem obvious, but it's likely this question comes up on account of C110, which is about fire hazard properties. C110 makes requirements of certain internal building elements, including wall linings. And that includes the internal lining of an external wall. So it has been suggested that C19 doesn't apply because C110 applies instead. But that's not the case. C19 applies and C110 applies as well. They are concurrent requirements. You have to meet your fire hazard properties under C110, which means a group number and other things spelt out in cause for respect C1.10. And in addition to that, you also need to meet your combustibility requirements of C1.9 if your building is of type A or type B construction. Someone might be thinking most internal linings of plasterboard and plasterboard wouldn't withstand that AS15 30.1 test. Perhaps not, but C19A contains a concession and lists a number of materials that can be used whenever a non-combustible material is required. And plasterboard is the first material on that list. So the internal lining is a part of the wall.