These solid, simple frames require no exterior brace. This is perfect for apartment dwellers and those who only need an air conditioner a few months of the year. It takes about an hour and some basic lumber and tools to construct these frames. Once built, your air conditioner can be installed and uninstalled in minutes. (Please note that window air conditioning units aren't intended to be permanently installed. These frames also make it simpler to remove them at the end of the warm season.)
The units pictured include unfinished plywood. However, this can be finished, painted or replaced with plexiglass or other materials, as the sheet lumber simply covers an opening and is not structural.
2X4s *(2 or less but the amount varies)
12 deck screws (or other long wood screws)
- These window sills in the picture are fairly deep, allowing for the use of 2X4s. You may be able to substitute other lumber for shallower sills.
Step 1: Take Measurements
Measure the height of your air conditioner. This height should be the box height and not include the lips on the bottom or the top.
Measure the height of the window opening. Take this measurement right up against the window because it will give the shortest height of this opening. (Again, mistakes reminded me that sills can angle away from the window, giving a height that is too long.)
Step 2: Cut the Frame Lumber
3 - width (including vents!) of air conditioner
2 - height of the window frame
Step 3: Starting the Frame
Create a rectangle by screwing another short piece of 2X4 between the long pieces at the other end, as shown. Make sure the corners are square.
At this point, it's a wise idea to put this rectangle into the window opening to make sure it fits. It should slide in and sit against the window framing. (If it's a little loose, you can use shims to help wedge it in place during installation.)
Step 4: Finishing the Frame
To figure out the placement of this piece of 2X4, lean the A/C so that the front vertical piece of the top lip lines up with the front edge of the wood frame. This is how the A/C will be oriented in the frame when complete, tipping the unit back.
While you're holding the A/C in place, take a look at the whole configuration to make sure it leans back sufficiently. Air conditioners must drain and are built to tip away from the window. If this lean appears to be too little (it really shouldn't be if the top and bottom lip are properly aligned with the frame), then you might want to rip this last piece of lumber, making it less than 3.5 wide, before screwing it in place.
If everything looks o.k., lay this piece of lumber in place and mark its position on the frame. Also, mark the top edge of the front lip where it will hit this piece of framing. (This mark is so you can measure for the piece of plywood covering the hole in the top of the frame.)
Remove the air conditioner from the frame and screw this piece of lumber in place. It would be good, at this point, to dry-fit the A/C into the frame just to make sure you are on-track.
Step 5: Covering the Top of the Frame
Screw the plywood covering in place.
Optional Consideration: I realized after I made the frame that it would be really nice to be able to open the window for a breeze to come through on cooler summer days instead of running the A/C. Consider stapling screening material over the side of the frame that faces outside. Then you can hinge the piece of plywood over the opening and install a latch for it so you can open it up when you want. Maybe add some weather-stripping to ensure a good seal with the door is closed.
Step 6: Installation
Slide the A/C into place and secure by running a screw or two through the lip. The weight of the unit should keep it in place but this is extra insurance. If the frame seems a little too loose to you, you can always use shims to wedge it tightly in place.
Fill any gaps around the opening. You can use a removable caulk, trim narrow pieces of foam insulation, or other ways to fill the gaps.