I'm trying to install a window unit air conditioner, but most of the installation instructions don't seem to work with this window configuration.

A little bit about the setup: The apartment is the 5th floor of a pre-war walkup building that has gone through various renovations, but none that have made it too modern. The window is about 30" wide, and is a metal frame.

There are two issues that make it hard to install a window AC unit:

  1. The window sill is made out of metal, so I can't nail or screw anything into it
  2. The base of the window has a thin (about 1/4") piece of metal jutting out of the buttom that's 2" high in the interior and 1.5" high in the exterior. This means I can't rest any part of the air conditioner on the sill - it ends up just resting on that piece of metal.

enter image description here

Most of the AC units I've looked at have brackets that get nailed into the window sill, and also require that they can sit flat against a ledge to fall into the brackets. Some examples of the instructions for the units for sale in my area are here:



Looking at my neighbors' apartments, it looks like their units have been there for decades, and some are propped up on things like phone books or 2x4s. I'm hoping to find a safer solution than that, so I don't accidentally drop a 50 pound AC unit 5 stories. I tinkered with it yesterday (using the LG unit), and the best I could come up with was wedging the AC in at an angle and closing the window, but that didn't seem safe or stable, and left a hole to the outside because the curtains weren't flush with the window.

Is it possible to install a window air conditioner in this setup, and how would I go about doing it?

  • Add a link to the image in an edit or a comment, and one of the higher rep users can add it into the post.
    – Tester101
    May 31, 2012 at 17:11
  • This Answer might be helpful.
    – Tester101
    May 31, 2012 at 17:12
  • Thanks @Tester101 - I actually looked at that, but I'm trying to use a window-mounted unit, not a portable unit.
    – David
    May 31, 2012 at 17:24
  • Same idea applies. You can build the frame any shape or size you need.
    – Tester101
    May 31, 2012 at 17:29
  • Here's a link to the (made in paint, so not great) image: dwor.in/window_problem.png I see now how the idea applies. It's a really good idea - I'd just need to find a lumber yard that can help out in Manhattan. Was hoping for something simpler, but that might have to be it.
    – David
    May 31, 2012 at 17:35

4 Answers 4


Since it sounds like it might be difficult for you to get to a lumberyard to build your own solution, you might be better off using a pre-made product. AC-Safe, makes Universal Air Conditioner Supports that might be useful in your situation.

enter image description here

The system requires you to screw the platform into the window sill (which may or may not be possible in your situation), then simply rests against the outside of the building to support the A\C unit.

I've also seen brackets that mount to the bottom of A\C unit itself, and offer support against the outside of the building (but I was unable to find an example online. I think Thermwell makes them).


I have the same NYC metal windows, and I'm using a universal bracket like the other commenter posted. I drilled two small holes in the bottom of my window frame (where the sash rests when the window is closed) and screwed the bracket into the wood below. The foot of the bracket rests on the stone window ledge.

It's weird that manufacturers don't provide instructions for these windows, since they seem to be pretty common in cities.


They are more expensive, but perhaps a "portable" unit might work better in this circumstance? It might still be a bit of a pain attach the hose to the window, but there'd be no saftey concerns with this. For example: https://www.amazon.com/Honeywell-Compact-Portable-Conditioner-Dehumidifier/dp/B079RH3G8Y


Could you use something like this?


It's been working well for us!

  • 3
    Link only answers are not very useful if the link dies. Please consider including a brief description of the product, and how it might help in the OP's situation.
    – Tester101
    Jun 5, 2014 at 11:55

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