In photos of skyscraper construction, I notice a big difference between our towers and those say in NYC. Ours seem to all be concrete, with a core. Those in New York seem to be a classic steel skeleton. Why the difference? Is there a geographic reason? What are the advantages/disadvantages?

Seattle gets both basic types, and many variations within those types, particularly variations on use of concrete. I'm no expert but there are many considerations -- construction cost, speed/availability of material procurement, speed of construction, column spacing, structural space between floors, seismic flexibility, stiffness of floors, ability or inability to cut or drill through the floor later on...

On many projects, the decision over structural type is left open well into the design.

What is an all concrete w/ a core skyscraper, does that mean like... concrete shear walls?? That's probably a stupid question but I'm curious!

Basically yes, to my understanding.

I think most new tall buildings throughout most of the world use steel. Am I wrong? It just seems new buildings tend to use steel, cause I don't see much concrete except here.

The structural system used is decided upon early in the design of a building. It is dependent on many factors like mentioned above.

Most of the pictures you are seeing in Seattle are residential. High rise residential projects in the northwest are concrete for several reasons. I list three but there are several more. One is because people are spending 500K to several million per unit and they are less likely to accept vibrations or noise transfer through the floors. Another reason is that the concrete available in the northwest is very high quality. (its strong and cheap, we have good aggregates). And third, concrete flat plate (no beams) buildings have a structural depth of typically 7-8 inches. This allows a shorter floor to floor ht and the developer can squeeze in another floor or two.

Several new office buildings are starting construction now. Most of them are going to be steel. Steel makes sense in office construction because the columns are typically regularly spaced(column layouts in residential are varied so the architect can hide them). This makes the design and construction of steel buildings cheaper because the pieces are all the same size. Also, office tenants are usually tolerant of some vibrations and noise transfer. And steel buildings are faster to build which means the developer can start charging rent.

A couple questions on apartment buildings with wood frame construction:

-What is the typical max floor count?
-How do these structures perform in earthquakes?
-How does these structures perform in fires? (i.e. without fire supression like in say... an earthquake).
-What is the typical structural life of the building?

A couple questions on apartment buildings with wood frame construction:

-What is the typical max floor count?
-How do these structures perform in earthquakes?
-How does these structures perform in fires? (i.e. without fire supression like in say... an earthquake).
-What is the typical structural life of the building?

The International Building Code allows 4 levels of wood. The city of Seattle strikes that and allows up to 5.

Wood frame structures typically perform very well in earthquakes as they are light weight and have lots of walls.

I cant really comment on the historical fire performance of wood structures....

Buildings are built with an assumed life of around 30 yrs. But with regular maintenance (ie reroofing, residing, painting) they can last well over 100yrs. Here in washington the key is keeping water out. Moisture will rot wood.

Bear in mind that the 5 floor count max does not include any concrete base floors. For example I'm on the 8th floor of an 8 story building. The bottom 3 floors are concrete while the top 3 are wood frame.

Mtoes, which Seattle office buildings under construction are steel framed? Do you know? It's been a long time since I've seen one rise here (WAMU Tower, I think). Wondering if 818 Stewart, 1918 8th, or the 8th/Westlake will be steel framed rather than concrete.

Bear in mind that the 5 floor count max does not include any concrete base floors. For example I'm on the 8th floor of an 8 story building. The bottom 3 floors are concrete while the top 3 are wood frame.

This is correct. The 5 floors refers to the wood portion only. Many here in seattle are 5 levels wood over 1 to 3 levels of concrete.

Mtoes, which Seattle office buildings under construction are steel framed? Do you know? It's been a long time since I've seen one rise here (WAMU Tower, I think). Wondering if 818 Stewart, 1918 8th, or the 8th/Westlake will be steel framed rather than concrete.

1918 8th is steel w/ concrete core (like wamu).
5th and Yesler is concrete until 4th floor then steel w/ concrete core.
9th & jefferson (Harborview MOB, 14 stories) is steel above level 5.


I am not sure about 8th & Westlake and 818 Stewart. I will look into those two...

1918 8th is steel w/ concrete core (like wamu).
5th and Yesler is concrete until 4th floor then steel w/ concrete core.
9th & jefferson (Harborview MOB, 14 stories) is steel above level 5.


I am not sure about 8th & Westlake and 818 Stewart. I will look into those two...
Thanks! You seem well informed.

1918 8th is steel w/ concrete core (like wamu).
5th and Yesler is concrete until 4th floor then steel w/ concrete core.
9th & jefferson (Harborview MOB, 14 stories) is steel above level 5.


I am not sure about 8th & Westlake and 818 Stewart. I will look into those two...

Asked about 818 stewart today and it will be concrete full ht.

Looked at the floor plans of 8th & Westlake online and they show steel columns so it looks like it will be steel w/ concrete core.

Thanks for the research. Answer me this (or anyone else): are there different grades of wood frame construction? I've seen where they slap up 5 floors of frame in a month whereas some take weeks/per floor (of similar footprint).

Case-in-point: the Borealis Apartments (Dexter and Denny) went up very fast, almost as if the panels were prefab or something, whereas the Veer Lofts (9th and Harrison) are moving a bit slower.

Just curious how frame construction is sometimes expedited.

Thanks for the research. Answer me this (or anyone else): are there different grades of wood frame construction? I've seen where they slap up 5 floors of frame in a month whereas some take weeks/per floor (of similar footprint).

Case-in-point: the Borealis Apartments (Dexter and Denny) went up very fast, almost as if the panels were prefab or something, whereas the Veer Lofts (9th and Harrison) are moving a bit slower.

Just curious how frame construction is sometimes expedited.

My guess would be that the apartments are using some kind of panelized system where entire wall sections are built on the ground or offsite and then put into place. This is often done in light gage steel construction. I have noticed these differences as well. The Domaine project on aurora creeped along very slow.

Hey, thanks for all the great info, everyone! Answers all of my questions. We have been hammered out here in Aberdeen by the storm, so I just got my power back on yesterday.:banana:

sorry to hear that. That storm hit you guys hard.