Best/strongest material to build a weatherproof shelf?

by Jorabi   Last Updated May 24, 2019 19:21 PM - source

I will be building a shelf on the outside of the house to hold a 120lb (18,000 BTU) air conditioner. The worrisome constraint is that the two shelf supports have to be 38" apart**. The 24" wide AC will sit in the middle of the 38" span.

I cannot find any information in layman's terms on how to know if the shelf will support the weight using various composite materials for the shelf. Does anyone have a suggestion for what to use, thickness, etc? I would like to use something that does not need painting.

** the reason for the wide span is the AC will be in the top pane of a double-hung window. The bottom pane still needs to be usable via its tilt-in ability, without obstruction from the shelf supports. The shelf will be right at the top of the bottom pane.

Answers 1

A couple ideas come to mind...

  • Two-by lumber wrapped in metal or vinyl
  • Aluminum box tubing or U-channel (2x2 or larger) resting on the support brackets with synthetic decking spanning the other direction
  • Synthetic decking resting on the support brackets with floating Aluminum angle extrusion bolted to the underside between the brackets
May 24, 2019 19:11 PM

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