Disclaimer: I'm not aware of any proper source. If there is one, then that would make a much better answer.
However if you're stuck deciding on your own, thinking about the function of the buildings can help decide on the height. For We Be Goblins I used the overall population mentioned and counted the squares of housing space to calculate how many goblins are in each house. In your case you could do it other way around. If these buildings provide living space, come up with a ration of how many tiles there ought to be per person on average for living space. If there's other functions they have to cover (library, weaponry, etc.) estimate how many tiles that would make up. Then count the tiles you have available as is, and add more stories until you have more than enough space to have all the functions covered.
Beware, this might be time intensive, but the results might be useful to other DMs running the adventure, if you can find a way to publish them, such as a forum.
An alternative that I've done once is drawing a small sketch of the building as you imagine it and then apply dimensions that you know are given (such as width and depth from the map) and calculate the proportion of width to height from a measurement of the sketch.