I have a few questions regarding tower that probably answered elsewhere already but sadly I couldn't come up with a search that not deliver way to many unrelated result.
1)What multiplier to the covenant prices (cov. 71) should be added for having the stones transported via ship to a isle near a major sea trade route?
2)How many standard size lab could fit in a average size tower per floor?
3)How many floor have the average size tower?
4)How are the size multiplier of covenant 71 would change answer 2 and 3?
5)How many years should be calculated that the construction takes without magical help?
A lab is 500 square feet. This is about 22' on a side. In Covenants, a small tower is four stories high (p. 12). City and Guild (p.68) says that a mason can build half a tower in a season. This isn't just one person, it's the mason serving as a foreman, with a number of laborers hauling materials. I'd say that one lab would fit per floor. The tower is 25' on each side, about 50' tall.
As for transporting stone, I'd estimate doubling the cost. Typically, building materials have to be transported some distance, you're just extending it somewhat.
Or you could just cast Conjure the Mystic Tower, and be done in two hours.
Thanks, I think I go with a 1 higher quality multiplier for the transportation because for more expensive build materials the transport cost shouldn't increase extra as with a direct x2 it would be.
For the construction its then 50L of the final cost without the extra for transportation per season with no construction are done during a winter season (unless the covenant is in a hot place where the break is probably summer)
As a slight addendum, note that the default map of a magi's sanctum (Covenants, pg. 105) is exactly this: one level of a tower.