Regulations and construction - questions

[bvpcvm]

Three questions for someone knowledgeable -

1. I've noticed several recently started projects are putting in a temporary barrier along the street to create a pedestrian walkway and sometimes even building a roof over it. I remember PAW did this, but now the Restoration Hardware, Gypsy replacement and Robert Ball projects in NW all have this. I'm wondering if a regulation change is requiring this?

2. Time to build a building. Several people have mentioned how slowly Sky3 has gone up. Looking back in old threads, it looks like it began in August 2014 - two and a half years ago. Q21 has also seemed to go very slowly. Meanwhile, other buildings, like The Dianne are shooting up. Maybe it's perception, but it seems like there's a big disparity in - I assume - construction techniques. If there are, say, 3 different main techniques and one is clearly fastest, why wouldn't the developer always choose the fastest one? It seems like the financiers behind Sky3 would want it to go up as fast as possible in order to maximize their ROI. What other factors would account for such a disparity?

3. Used to be that 6 stories was the maximum for wood framed buildings. Lately there have been numerous 7-story proposals. I presume these will be wood frame, since, otherwise, I can't see how 7 stories would pencil out, given that they'd have to use concrete as I understood things. Has some regulation changed on this?