Plural in ‘Flat’, ‘Unit’, ‘Apt’, ‘Ste’

Question

This and this are examples of addresses in the UK.

• Unit 1–3, ×× Corporation Street, Birmingham, B4 ×××, United Kingdom
  It covers Units 1, 2 and 3. (Or ‘it covers Unit 1, 2 and 3’?)
• Unit 2–3, ×× Bard Road, London, W10 ×××, United Kingdom
  It covers Units 2 and 3. (Or ‘it covers Unit 2 and 3’?)

This and this are examples of an addresses in the US.

• ×× Country Club Dr, Ste 2–4, Palm Desert, CA 922××, United States
  It covers Suites 2, 3 and 4. (Or ‘it covers Suite 2, 3 and 4’?)
• ×× Niles Ave, Ste 2 & 3, Bakersfield, CA 933××, United States
  It covers Suites 2 and 3. (Or ‘it covers Suite 2 and 3’?)

Usually, we say pages 3–6 (pp. 3–6) and Chapters 3–6 for a book. In terms of plural room numbers in a sentence, is ‘I live in Flats 2–3’ or ‘I live in Flat 2–3’ correct? Is it because the expression of the address is special, so we keep the singular form?

Answer 1

For the addresses, we don't know what it actually means and we don't care. A postal address is just a magical incantation that allows a letter to get to its destination. It is possible that Unit 1—3 is the third unit of block 1.

However, these might also be merged addresses. These are business addresses. The first one looks like the address on an industrial estate. The landowner divides the land into "units" and businesses can hire these units. A large business might hire two or three units that are next to each other, but only provide a single entrance, and so their address might be "unit 1—3". It seems likely that because they only provide a single entrance, the units have been combined into a single "unit" with identification code "1—3". This business covers the space for units 1,2 and 3.

It is very rare for this to be done for residential addresses. Flats will stay as separate flats, with different families in each. In the super-rare case of somebody actually buying several neighbouring flats and joining them together, then you could write "flat 1-2". It is more likely that they will just keep one number and drop the other. But it is so rare that there isn't any established usage.