Why so many mid-rise buildings?

You may have noticed a trend in mid-rise development from small cities to large cities all across the fruited plains. Even larger cities with extremely built up city centers featuring 30-50 story towers are seeing a lot of developments with mid-rise structures. Builders are often choosing these shorter towers even when local zoning allows for high-rises. So what gives?

As buildings get taller, they require more and more engineering to ensure the tower is stable and can support its own weight. This is why skyscrapers are so expensive to build. But high-rise buildings in the 10-15 story range are low hanging fruit for engineers and architects. We have been building these for 150 years. Why would a developer choose to build a mid-rise project on an expensive property when zoning allows for 10-15 stories? Well, it often comes down to cost and construction time. Current building code allows for residential wood framed structures of up to 5 stories so long as the height is 85 feet or less off the street. There is some minor wiggle room but that is the general idea. Mid-rise structures of 6-8 floors can typically fit into an 85 foot height envelope. Anything taller than that generally requires more traditional concrete and or steel framed structures. 

The Aria on West 6th, June 2020.
2 level type one podium under 
5 levels of wood frame

So the trend has been to build a podium of concrete and or steel to a height of 1-3 stories above ground and then add 5 stories of wood frame up top to stay under that 85 foot envelope and squeeze as much as possible onto the land. This modern mid-rise formula is much less expensive to build for a few reasons. The engineering and design required to support the structure is far less complex and the wood frame portion can be built with a more readily available labor force. Wood framing also goes up faster in general than concrete. To build a 10 story building versus an 8 story is much more expensive and time consuming and thus may not be a financially rewarding for the developer. This is largely why you are seeing high-rise residential buildings going a bit taller to the 12-16 story range to maximize the land use and balance the greater expense of type one concrete construction.

You can see this decision making in a recent development proposal here in Vancouver on Block 11 of the Waterfront. The FAA height limit for the block is more than 140 feet which would easily accommodate a 12-14 story residential tower. Holland Partner Group, a Vancouver based developer of urban residential proposed both a 12 story and 8 story tower with the latter being a wood frame over podium design. After running the numbers they decided to pursue the mid-rise option with 100 fewer units. There is some formula these developers use to determine how long it takes to recover the extra costs of type one construction with the extra units gained and in this case Holland felt the numbers don't add up for the high-rise. Of course another developer might think it pencils fine for the taller structure. Short game, long game, high risk, low risk it all goes into the mix and many developers these days are liking the mid-rise option. 

Other advantages to mid-rise designs include a less intrusive build that in smaller cities might be easier to sell to citizens wary of a large built up landscape. Daylight can filter down to the street easier with shorter towers even if the building rises straight up off the sidewalk. This lends itself to creating a more walkable neighborhood. 

I believe we will continue to see more mid-rise wood frame over podium projects in cities of all sizes all across the country as we attempt to increase our housing stock which is pretty low in some areas, including Vancouver, WA.