4 ms·

Isn't there an optimum of about 8-12 stories for any sort of building, before the cross section of plumbing and elevator shafts make it less economical?

by kleton 3y ago

bombcar 3y ago
The optimum is based on land value, clearly, because in places where the land is effectively free or incredibly low cost, buildings don't seem to naturally get above 2 or 3 stories. So somewhere between 3 and 12 stories is a local optimum, and it's probably about where you need additional "machine floors".
- bluGill 3y ago
  Where land is free 5 floors is the optimum just because nobody will accept more than 3 without expensive elevators (it may not even be legal if you would accept it!). Most people are willing to pay a little bit more for a larger foundation just for less floors. For car oriented locations 1 floor is optimal because the type of building that can handle more than one level of cars is so expensive you want to just build a large parking lot. (In theory the humans could be in taller buildings, but the space used for humans becomes a rounding error, and so you may as well avoid the expensive elevator)
jupp0r 3y ago
This is obviously a function of the price of land, otherwise you wouldn't see very large high rises in Manhattan or similar.
bluGill 3y ago
There are lots of different factors the come into play as you go higher. Above 3 floors you need elevators for the disabled, while shorter buildings often cant get by without. (check with a lawyer for what your local law says - I've been told that the 3 floor isn't what the ADA doesn't actually say the highest is, just what most consider it to say). Even without disability laws, people generally want elevators to go higher. Conventional wood framing is the cheapest, but 5 is about the max floors you can get. Brick framing can apparently get you to about 10 floors. There are lots of other construction methods - check with a proper civil engineer for what the limits and costs of each are. Somewhere around 6-15 floors your city water will no longer have enough pressure and so your building will need booster pumps. Similarly, drain water needs special care to ensure the falling water doesn't burst the plumbing. You local fire may code allow for less strict standards if the fire department ladder trucks can just drive up to each window and rescue someone in a burning building. If that cannot happen people need to get down the stairs in case of fire (I've always wondering how the disabled will do this) so you need to ensure those stairs can be used in case of fire. Floor space per person is also a factor. Richer people tend to be willing to pay for more space than poor people, and poor people tend to have more kids. Thus if you make larger apartments you don't need as much elevator space. This one is tricky though as rich people tend to prefer newer buildings so you might discover that when the building gets old you can't rent some apartments because of the building max occupancy. Still, office buildings tend to have a lot more people per area, and they are more likely to leave at the same time, so I don't think space per person can be a big factor. (but school dorms need to consider all students going to class at the same time) As the person paying for a building you get to optimize those factors (generally for profit, but you can pick other considerations). Good luck.

Isn't there an optimum of about 8-12 stories for any sort of building, before the cross section of plumbing and elevator shafts make it less economical?

by kleton 3y ago

Isn't there an optimum of about 8-12 stories for any sort of building, before the cross section of plumbing and elevator shafts make it less economical?

bombcar 3y ago

The optimum is based on land value, clearly, because in places where the land is effectively free or incredibly low cost, buildings don't seem to naturally get above 2 or 3 stories. So somewhere between 3 and 12 stories is a local optimum, and it's probably about where you need additional "machine floors".

bluGill 3y ago
Where land is free 5 floors is the optimum just because nobody will accept more than 3 without expensive elevators (it may not even be legal if you would accept it!). Most people are willing to pay a little bit more for a larger foundation just for less floors. For car oriented locations 1 floor is optimal because the type of building that can handle more than one level of cars is so expensive you want to just build a large parking lot. (In theory the humans could be in taller buildings, but the space used for humans becomes a rounding error, and so you may as well avoid the expensive elevator)

jupp0r 3y ago

This is obviously a function of the price of land, otherwise you wouldn't see very large high rises in Manhattan or similar.

bluGill 3y ago

There are lots of different factors the come into play as you go higher. Above 3 floors you need elevators for the disabled, while shorter buildings often cant get by without. (check with a lawyer for what your local law says - I've been told that the 3 floor isn't what the ADA doesn't actually say the highest is, just what most consider it to say). Even without disability laws, people generally want elevators to go higher. Conventional wood framing is the cheapest, but 5 is about the max floors you can get. Brick framing can apparently get you to about 10 floors. There are lots of other construction methods - check with a proper civil engineer for what the limits and costs of each are. Somewhere around 6-15 floors your city water will no longer have enough pressure and so your building will need booster pumps. Similarly, drain water needs special care to ensure the falling water doesn't burst the plumbing. You local fire may code allow for less strict standards if the fire department ladder trucks can just drive up to each window and rescue someone in a burning building. If that cannot happen people need to get down the stairs in case of fire (I've always wondering how the disabled will do this) so you need to ensure those stairs can be used in case of fire. Floor space per person is also a factor. Richer people tend to be willing to pay for more space than poor people, and poor people tend to have more kids. Thus if you make larger apartments you don't need as much elevator space. This one is tricky though as rich people tend to prefer newer buildings so you might discover that when the building gets old you can't rent some apartments because of the building max occupancy. Still, office buildings tend to have a lot more people per area, and they are more likely to leave at the same time, so I don't think space per person can be a big factor. (but school dorms need to consider all students going to class at the same time) As the person paying for a building you get to optimize those factors (generally for profit, but you can pick other considerations). Good luck.