I have a steel post that is 4" x 4" x .250" wall. it is exposed in the Florida keys and want to replace with aluminum. It sits on a concrete floor and supports a concrete floor above. I have no idea on the load. Make dimension is 8" x 8" as that is the width of the concrete beam above.

i have not found a "calculator" to run this for me. thoughts? Thanks!

  • 3
    Will need a structural engineer. Guessing since I don't have a cement floor above my head, at least two or three times the size including wall thickness, maybe even more. Those steel posts looking better now I guess.
    – crip659
    Sep 14, 2022 at 19:11
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    i think you may be correct! dealing with hurricane winds and 185 mph codes! thanks
    – Bob Wright
    Sep 14, 2022 at 19:18
  • 1
    "No idea of the load" usually means it is more than enough to flatten you. Mistakes are not recommended.
    – crip659
    Sep 14, 2022 at 19:55
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    In a sea coast environment , aluminum offers no significant corrosion advantage over steel. Sep 14, 2022 at 20:53
  • 2
    Is your worry rust and failure or aesthetics? Could work on weather proofing instead, even exposed as it is you could prevent it rusting away with anual maintenance
    – Chris
    Sep 15, 2022 at 1:21

2 Answers 2


This question cannot be answered as asked. So let me answer with what you need to do:

  1. Consult a local engineer (i.e. one with a P.E. after his/her name) and who is qualified in the area of structural analysis you are interested it. The engineer can calculate the load and then give you a design of a properly sized support structure. If you want it to be Aluminum, be sure to point that out.

  2. Hire a suitable contractor to do the actual work for you since specialized equipment and techniques are almost certainly going to be required.

This is absolutely not a DIY sort-of project and the stakes for you and anyone else using your property are quite high.


Alumimium is about 1/4 as strong as steel by volume, so a 4x4 post with one inch walls would be an adequate replacement for your post with quarter inch walls (at that thickness it's probably cheaper to get a solid square bar).

but your post may be been overspecified to withstand some rusting. and so a lesser aluminium post may be usable. consult an engineer.

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