. >> reporter: jason korb is the architect of the ascent building.eam was careful to source their wood from sustainably managed forests. had you ever designed a timber building before? >> never once. we went big. >> reporter: what was that process like? >> i think we knew about 5% of what we needed to know when we started in march of 2018. and i liken it to going to graduate school for two years. >> reporter: part of what korb had to figure out was how to get the city of milwaukee to approve his plans. the tallest mass timber buildings right now are in europe, including the very tallest, an 18-story tower in norway. but the tallest buildings in the u.s. are between 7-10 stories, in part because american building codes he been slow to catch up. architect jason korb spent more than two years proving his 25-story building would be safe, including answering the question often on people's minds: how will the structure hold up in a fire? the ascent team worked with the u.s. forest service to do extensive fire testing, the first of tir kind ever conducted.