3 ms·

I'm excited for more wooden buildings, but the claim that "Compared to cast-in-situ concrete, wood makes it possible for construction time to be slashed by half

I'm excited for more wooden buildings, but the claim that "Compared to cast-in-situ concrete, wood makes it possible for construction time to be slashed by half" seems very optimistic. There's a building boom going on around my office. The steel and concrete office tower next door is by far "sprouting" the fast. On the other side is a residential tower where half of the building is a 20+ floor concrete tower, and the other half is a 5-floor wood frame structure. The concrete tower is going up faster, despite this being the same construction project. Perhaps what I'm missing is that a CLT build is more similar to steel construction than a wood frame building. Perhaps a real civil engineer can weigh in...

foofoo55 8y ago
I'm not a civil engineer, but I do know that a CLT (cross-laminated timber) building can get built faster because many parts are pre-fabricated panels. The University of British Columbia (UBC) built a 18-story wooden building (which is shorter at 54 metres), and it was built relatively fast: https://archinect.com/news/article/150029630/the-world-s-tallest-wood-building-opens-to-residents-at-university-of-british-columbia https://archinect.com/news/article/150029630/the-world-s-tal...
- buildbot 8y ago
  I got to watch that building be constructed during my masters, it was pretty amazing to watch how quickly it was constructed. Fun fact, UBC has like 3 18-19 story dorms with million dollar views of the entire surrounding area.
- ggcdn 8y ago
  This building has two concrete cores (elevator/stair shafts) for lateral resistance that were built ahead of time, and then the wood gravity system came later, So it kinda took more time than normal. Another fun fact - alot of that nice looking wood had to be covered up with drywall for fire code compliance.
owengee 8y ago
Concrete setting times depend on ambient temperature. Too cold and concrete takes longer to achieve the necessary strength to start the next level. Admixtures and other techniques can improve this. So the claim for taking less time than a _concrete_ building is plausible for this location (I assume it's pretty cold compared with other climates). However like you mentioned, a _steel framed_ building would be similar in build time, since the elements can be hoisted and joined in the same way as a CLT building. But that also depends what your slabs are. Most steel framed buildings use concrete slabs, which need to be poured and set, but with high early strength concrete and propping, this takes less time than a conventionally formed concrete building. Concrete buildings can go up really fast, I've seen 5-6 day cycles on jobs. It depends on the complexity of the structure and again the ambient temperature (among other things). So yes concrete can go up faster than CLT as you noted. As an interesting side note, the article mentions that the top floors of this CLT building use concrete for mass to limit swaying.
grp000 8y ago
I used to work in Construction Management on the structural concrete side, so I can weigh in (a little) on possible reasons why the CIP (cast in place) tower seems to be going up faster. Generally, CIP vertical structures have minimal changes from level to level, so as the building goes up, the construction crew (generally Carpenters, Rebar/PT laying crew, and concrete placers/finishers) will become much more efficient at their work. Also, there will be minimal 'fine' work on creating floor plans on a CIP deck, it will be a primarily flat surface, excepting stub walls (for steel stud walls), utility penetrations, possibly other stubbed elements for vertical shafts and etc., elevation cuts, and sloping. The structural concrete sequencing is such that the bare core structural body is formed first, and other trades will populate it to create the finished product later on. With wood framing, I am not too familiar with the process, but I believe many of the stud walls have structural properties, and in general much more of the finished 'shape' of the floor will be done in the wood framing process from level to level.
atombender 8y ago
I think the claim is plausible. If you've ever watched Grand Designs, a lot of the houses (especially the cheaper or less traditional ones) use prefab pieces and are incredibly fast compared to traditional timber frames with poured concrete. In the last few seasons, in particular, a bunch of the houses use pre-built wall (and even floor) "cassettes", also called closed-panel frames, that come with everything from the factory -- not just structural framing, but layers of insulation, breather membrane, vapor barrier, etc., complete with inside-facing gypsum drywall -- and simply lock together. There are also lots of examples of custom off-site-engineered steel or wood pieces that are CNC-machined (almost always shipped from Germany or Switzerland), and also very fast to install, partly because they can machine them to a high precision. At the construction site, it's just assembly.
jdsully 8y ago
Seattle is just now allowing wood construction in high rise buildings. Previously they were an early adopter in mid-rise buildings which is why you see a lot of apartment buildings with exactly 6 stories around (1 concrete ground, 5 wood as allowed by the building code). https://www.prnewswire.com/news-releases/washington-state-to-allow-mid-and-high-rise-mass-timber-buildings-300760329.html https://www.prnewswire.com/news-releases/washington-state-to...
- deleted 8y ago
  [deleted]
- walrus01 8y ago
  In South lake Union Seattle also has a lot of midrise because of height restrictions around the space Needle. The needle is not actually that tall, the city is afraid that rampant real estate developers could completely hide it in the skyline.
  - lenocinor 8y ago
    Actually I think it's because of the seaplane flight path https://www.seattle.gov/Documents/Departments/OPCD/OngoingInitiatives/SouthLakeUnion/SouthLakeUnionEISAppendixFAdditionalFlightPathAnalysis.pdf https://www.seattle.gov/Documents/Departments/OPCD/OngoingIn...

foofoo55 8y ago

I'm not a civil engineer, but I do know that a CLT (cross-laminated timber) building can get built faster because many parts are pre-fabricated panels. The University of British Columbia (UBC) built a 18-story wooden building (which is shorter at 54 metres), and it was built relatively fast: https://archinect.com/news/article/150029630/the-world-s-tallest-wood-building-opens-to-residents-at-university-of-british-columbia https://archinect.com/news/article/150029630/the-world-s-tal...

buildbot 8y ago
I got to watch that building be constructed during my masters, it was pretty amazing to watch how quickly it was constructed. Fun fact, UBC has like 3 18-19 story dorms with million dollar views of the entire surrounding area.
ggcdn 8y ago
This building has two concrete cores (elevator/stair shafts) for lateral resistance that were built ahead of time, and then the wood gravity system came later, So it kinda took more time than normal. Another fun fact - alot of that nice looking wood had to be covered up with drywall for fire code compliance.

owengee 8y ago

Concrete setting times depend on ambient temperature. Too cold and concrete takes longer to achieve the necessary strength to start the next level. Admixtures and other techniques can improve this. So the claim for taking less time than a _concrete_ building is plausible for this location (I assume it's pretty cold compared with other climates). However like you mentioned, a _steel framed_ building would be similar in build time, since the elements can be hoisted and joined in the same way as a CLT building. But that also depends what your slabs are. Most steel framed buildings use concrete slabs, which need to be poured and set, but with high early strength concrete and propping, this takes less time than a conventionally formed concrete building. Concrete buildings can go up really fast, I've seen 5-6 day cycles on jobs. It depends on the complexity of the structure and again the ambient temperature (among other things). So yes concrete can go up faster than CLT as you noted. As an interesting side note, the article mentions that the top floors of this CLT building use concrete for mass to limit swaying.

grp000 8y ago

I used to work in Construction Management on the structural concrete side, so I can weigh in (a little) on possible reasons why the CIP (cast in place) tower seems to be going up faster. Generally, CIP vertical structures have minimal changes from level to level, so as the building goes up, the construction crew (generally Carpenters, Rebar/PT laying crew, and concrete placers/finishers) will become much more efficient at their work. Also, there will be minimal 'fine' work on creating floor plans on a CIP deck, it will be a primarily flat surface, excepting stub walls (for steel stud walls), utility penetrations, possibly other stubbed elements for vertical shafts and etc., elevation cuts, and sloping. The structural concrete sequencing is such that the bare core structural body is formed first, and other trades will populate it to create the finished product later on. With wood framing, I am not too familiar with the process, but I believe many of the stud walls have structural properties, and in general much more of the finished 'shape' of the floor will be done in the wood framing process from level to level.

atombender 8y ago

I think the claim is plausible. If you've ever watched Grand Designs, a lot of the houses (especially the cheaper or less traditional ones) use prefab pieces and are incredibly fast compared to traditional timber frames with poured concrete. In the last few seasons, in particular, a bunch of the houses use pre-built wall (and even floor) "cassettes", also called closed-panel frames, that come with everything from the factory -- not just structural framing, but layers of insulation, breather membrane, vapor barrier, etc., complete with inside-facing gypsum drywall -- and simply lock together. There are also lots of examples of custom off-site-engineered steel or wood pieces that are CNC-machined (almost always shipped from Germany or Switzerland), and also very fast to install, partly because they can machine them to a high precision. At the construction site, it's just assembly.

jdsully 8y ago

Seattle is just now allowing wood construction in high rise buildings. Previously they were an early adopter in mid-rise buildings which is why you see a lot of apartment buildings with exactly 6 stories around (1 concrete ground, 5 wood as allowed by the building code). https://www.prnewswire.com/news-releases/washington-state-to-allow-mid-and-high-rise-mass-timber-buildings-300760329.html https://www.prnewswire.com/news-releases/washington-state-to...

deleted 8y ago
[deleted]
walrus01 8y ago
In South lake Union Seattle also has a lot of midrise because of height restrictions around the space Needle. The needle is not actually that tall, the city is afraid that rampant real estate developers could completely hide it in the skyline.
- lenocinor 8y ago
  Actually I think it's because of the seaplane flight path https://www.seattle.gov/Documents/Departments/OPCD/OngoingInitiatives/SouthLakeUnion/SouthLakeUnionEISAppendixFAdditionalFlightPathAnalysis.pdf https://www.seattle.gov/Documents/Departments/OPCD/OngoingIn...