Originally posted by Hobo Misanthropus:

There are reinforced wooden poles and beams later, at the Iron stage, but it won't help you too much. If you want to build tall, you need to use Iron Cage wall roof and floor pieces, and they cover those up with Wood, stone or Black marble pieces to make essentially Iron Reinforced wood or concrete. This essentially means building something twice, once a skeleton of iron, and then the actual structure around it. If you're not using devhacks, the resource cost of building like this is astronomical.

Pretty sure iron cages have the same structural integrity as wood iron poles, so using the poles is good enough