The Straits Times reported on a case in which a commercial unit at D'Leedon condominium in which the ceiling area (818 square feet) is much larger than the floor area (619 square feet) (https://www.straitstimes.com/singapore/courts-crime/property-buyer-loses-590k-suit-against-real-estate-agent-era-in-rare-case-of-size-disparity, 9 May 2025).
The difference arises because at least one of the walls of the unit is not vertical.
However, under the law, the lot area is the bigger of the ceiling area and the floor area.
If a buyer thinks that the lot area is floor area, he will be in for nasty surprise.
Firstly, the buyer will have overpaid for the lot if he simply looks at the price per square foot of the lot area. For comparison purposes, should the price per square foot be based on the lot size or floor area or neither?
Secondly, the buyer may end up with a much smaller lot, in terms of floor space, than he thinks.
The problem is not limited to lots in which the ceiling area is larger than the floor area.
If the floor area is much larger than the ceiling area, it is also difficult to utilise the floor area adjacent to the non-vertical walls; it's essentially wasted space.
Even two vertical walls meeting at an acute angle can give rise to a small area that is of no practical use to the occupant. Such tiny spaces count toward the area of a lot and helps the developer to maximise his income-generating gross floor area of the land.
Conclusion: architects should not design buildings in which the walls are not vertical or the walls meet at acute angles. They serve no useful purpose to buyers or occupants.