Quote:
Originally Posted by Busy Bee
Engineers figured out how to do that a long time ago and they've gotten pretty good at it. We're storing cars down there not sensitive paper documents anyways so an ounce of water infiltration isnt that big of a deal. I think the real motivation is the cost of excavation versus the savings of going the podium route.
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Not just cost but time. If you have to dig down before you can go up, that adds months (or years) to the timeline. Time is money
and risk - if the rental market is good now, you don't want to be delivering new apartments 30 months from now when there could be a recession.
This is partly why Chicago engineers developed the top-down construction method, so you can build vertically at the same time you're digging down. Of course, that approach adds up-front cost with expensive secant walls etc, and works best on large sites.
For North Union it looks like there was a package deal - they moved at lightning speed on 920 which has a parking podium, and they will deliver those units relatively soon. While that's going on, they can build 868 with underground parking using the cheaper but slower bottom-up method. That way they stagger the delivery of new apartments which hedges the risk nicely - there probably won't be recessionary conditions for
both building deliveries, so at least one of the two towers will start off with strong financial returns.