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As a non architect, I always wondered if it is cheaper to build two high rises versus one high rise. (example inside)

dassouki

Let's say you want to build 160 apartment units. for the sake of argument, let's assume only two types (2 bed and 3 bed units).

 

Would it be cheaper to build 2 x 20 story buildings with 4 units each units on each floor, or one 20 story building with 8 units on each floor? 

 
Sep 12, 11 2:36 pm
drums please, Fab?

1 is cheaper than 2

Sep 12, 11 3:47 pm  · 
 · 
cipyboy

i say 1 over 2... 

Sep 12, 11 3:54 pm  · 
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Depends on the cost of real estate and fire requirements.

One really big three-story building (brick-on-concrete with steel) would run about $110 a square foot. One 20-story building (brick-on-concrete with steel) would run about $130 a square foot.

Assuming each unit averages about 1500 square feet (38' by 38'), a "long-hallway" style 3-story building would need about 2.6 acres. (I had to increase the units to 162 just to simplify maths.

A single large 20-story building, 9 units per floor, would need about 0.51 acres.

Now, if your land is going for say $800,000 an acre...

Low-rise building would be $26,730,000.
High-rise building would be $31,200,000.

Low-rise building land price would be $2,080,000.
High-rise building land price would be $408,000.

In this case, there's a tipping point, when land reaches about $2,275,000 an acre, when the high-rise will be more economical.

Mid-rise buildings, however, are almost always cost-competitive to low-rise buildings if you ignore parking requirements. Four-to-eight story buildings are only about $5-10 more a square foot.

For an 8-story building, you'll need about 0.97 acres.

They run about $111 a square foot (brick-on-concrete with steel). That's $26,973,000 plus $776,000. This is about $110,000 cheaper than the low-rise building.

When looking at high-rises, 2 buildings will always be more expensive than one, due to land costs, than 1 unless you're building pencil towers.

Sep 12, 11 4:28 pm  · 
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Now, to add a little bit of complexity to this... parking requirements will kill your budget.

Let's use these simple ratios for parking (units-to-parking spaces):

High-rise: 1:0.1
Mid-rise: 1:0.3
Low-rise: 1:0.75

High-rise: 16 garage parking spaces would be about $15,000 per parking space or $150,000
Mid-rise:  49 garage parking spaces would be about $15,000 per parking space or $735,000
Low-rise: 113 surface parking spaces would be about $5,000 per parking space, plus  land at 300 square feet per space, or $565,000 plus $616,000 for land with a total of $1,181,000.

With parking, the land threshold price would be about $1,625,000 per acre instead of $2,275,000 with mid-rise still being the most cost-effective building pattern.

That puts our grand totals for each building at the following:

High-rise: $31,758,000
Mid-rise: $28,484,000
Low-rise: $29,426,000
 

Sep 12, 11 4:46 pm  · 
 · 

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