I don't know of any grammar rule for this. Maybe someone else does. Besides, if there were a grammar rule, you'd have to trust that everyone followed it. Trusting a buliding contractor or furniture salesperson to follow an obscure rule of grammar would be crazy.
Anyone concerned with the actual measurements of the sofa would write something like one of these:
You may sometimes hear Americans say the word "height" as if it ends with a TH. They do this because they learned to pronouce the word incorrectly when they were young. They made a mistaken mental connection between height and width and depth.
Width and depth do end with a TH sound, but height ends with a T and rhymes with bite.