20 The difficulty with these submissions is that they raise questions of fact which are not suitable for determination before a final hearing. The concept of a latent defect in a building is used in the authorities in this area in the sense of something which is not known or manifest. They are the two sides of the one coin. In this area, the concept of what is manifest extends to what is not known but would be discovered through the exercise of reasonable diligence. A defect which is not known or manifest in this sense is latent. Equally, in my view, a defect is latent if it is not known or manifest in this sense. In my view, there is no additional requirement that in order for a defect to be latent it must not be visible, or must be concealed or hidden, although, of course, a defect which is visible and not hidden may be manifest in the sense of being discoverable with reasonable diligence. Moreover, a defect may be, and often will be, different from the physical thing which may be observed. For example, there may be a latent defect in the design of a building where a temporary external wall is too thin to carry a load, even though the thickness of the wall and the size of the roof it carries is plainly visible. (Sherson & Associates v Bailey at 66,505). The defects alleged by the plaintiff in this case are, primarily at least, defects of design. The principles as to when economic loss is first suffered through latent defects in a building are the same whether the defect is one of construction or design. (As to defects of design, see e.g. Pullen v Gutteridge Haskins & Davey Pty Ltd; Sherson & Associates v Bailey; and Bryan v Maloney. As to defects of construction, see Sutherland Shire Council v Heyman).