In order to constitute waiver of breach a waiver of it as ground of action for damages, the party not in default must know of the facts which constitute such breach, or must have the means of knowing them. A pavment for machinerv made before it is completed, does not waive a claim for damages for defects in machinery or for delay in completing it.1 Thus taking possession of a building does not waive defects which cannot be detected by inspection at the time but will develop by use, such as defects in plastering, by reason of which the plaster subsequently falls,2 or defects in varnish.3 So the use of finishing material does not waive a claim for damages for defects not then discoverable which develop as it seasons.4