There are various ways of saying something critical and unpleasant but true, and we employ different ones depending on such things as who we are talking to, and their sensitivity to criticism and irony.
Here are three ways of saying this, sounding successively softer: 1. Whoever built this building neglected to install drainage. - bald statement of fact. 2. It appears that whoever built this building neglected to install drainage. - but, of course, appearances may be deceptive (unlikely in such circumstances). 3. It would appear that whoever built this building neglected to install drainage. - the conditional attempts to soften 2., but brings with it the suggestion that the lip is curled (that the speaker is being ironic), so some people would be more offended by 3. than 2.
1. is for people who are blunt and direct. This is an unpleasant fact and we must face up to it.
2. and 3. is for people who either want to soften a blow, or add a slight ironic twist to the presentation of the unpleasant fact. These would both be ways often employed by people talking to third parties, people not concerned with the building, its financing, and its possible uses, people for whom such a gaffe by the architect may be seen as amusing.