If you buy an Air Conditioner with unorthodox window system then you might stumble upon this question , “ How Do You Install A Window Air Conditioner In A Sideways Window?”Do you face a problem when it is about to install a window air conditioner in a sideways window? If yes, then do not worry at all. Here I am with ultimate guidance and basics of how you can install a window air conditioner in a sideways window.

How Do You Install A Window Air Conditioner In A Sideways Window

The Ways You Can Install A Window Air Conditioner In A Sideways Window

This writing aims at providing a step-by-step guideline about how to install a window air conditioner in a sideways window.

There are the things that you will need for installing a window air conditioner in a sideways window.

  • First and foremost, you will need an air window conditioner.
  • Then you will need plexiglass.
  • Weatherstripping.
  • A measuring tape.
  • You will need a power drill.
  • A scissor.
  • Screwdriver.
  • Table saw.
  • Screws.

Now let me tell you a bit about sideways windows.

Sideways Window

A sideways window is a kind of window which slides open or closed. This kind of window is generally found in areas where the space is limited, for instance, apartments. You can open a sideways window from the top, bottom, right side as well as left side, and even from the window centre.

A sideways window is a great choice if you want to have more sunlight in your home.

Now, as you have the basic idea about window air conditioners and sideways windows also, we will now look into how you can install a window air conditioner in a sideways window. 

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Select An Installation Place

The installation location that is best for your window unit is near a wall-mounted power source that is compatible with your AC unit. Thus you will have enough power supply for the window air conditioner that you have purchased.

We also ask you to check and ensure if the window sill is okay or not. Because you have to ensure that the window sill is anyhow not damaged as well as broken.

Then you need a very strong surface to mount the customised window frame and air conditioning unit. 

Take The Measurement Of The Air Conditioner 

First things first, remove the side panels of the air conditioning unit. Generally, these are attached to the unit used by screws. So use a screwdriver and loosen as well as remove them.

Secondly, take a measurement of the unit. Measure the unit with width, including any protruding parts, for example, vents. Measure the height, excluding the lips on the bottom as well as the top rail. Write down the dimensions.

Take A Measurement For The Frame

Take measurements with the width and thickness of the window sill and have a short note of the measurements. Next, measure the window frame’s height from head to toe, that means from the bottom corner to the top corner.

Then subtract the height of the AC from the window sill’s height to get an idea of proper dimensions for the frame. 

Construct The Custom Frame

First of all, you will need lumber and it has to be as wide and thick as the windowsill. Take two long pieces of wood. Then cut them to the windowsill’s height by using a table saw. Next, take two shorter pieces of lumber and mark the air conditioner’s width.

Cut the pieces of lumber in an appropriate way using a table saw. Mark the window air conditioner’s height from the bottom side of the longer pieces of lumber. Then join the lumber pieces. Shorter lumbers need to be joined to the uppermost side of the longer pieces of lumbers.

Next, join the other short lumbers at those points where you marked the air conditioner’s height. Be assured about the fact that the corners are square and the joints are strong. Once you are done with all of the above-mentioned things, fit the frame to the window and make sure that it is fitted properly.

If you do not have enough time, if you do not have the patience or skill to construct the frame for your window air conditioner unit, no worries then. There is an easy way too. You can find both the window kit and installation kit online, which you can use instead of installing a window air conditioner in your sideways window. 

Install The Frame And The AC Unit

If you use the lumber in the correct width and thickness, then the frame will be fitted properly onto the windowsill of the sideways windows. In spite of that, you may need to fortify the attachment of the frame on the sill with screws.

It should fit in such a way that when you close the sideways window, the outer sill of the window fits onto the outer side of the frame. Then install the window air conditioner.

Take help of a partner, lift up the window air conditioner into its place accordingly and set its bottom on the windowsill so that the channels which are at the bottom can be aligned to the windowsill.

Slide the AC forward until the bottom side of the lower frame is in touch with the top rail’s bottom. The inner edge of the top rail needs to be on the outer side of the frame’s bottom. In this way, the frame can prevent the window air conditioner from leaning more.

Screw Plexiglass Onto The Frame

Who does not want sunlight entering their house? We all want and love natural lights. No light can defeat sunlight. And if you are one of them who wants as much natural light entering the house as possible, then this is the right article for you.

Once you are done with the AC installation, then screw plexiglass onto the wooden frame. You can also use plywood if you want in place of plexiglass. Both work the same. Mark the frame’s dimensions on the plexiglass or plywood and cut it accordingly. 

Install Weatherstripping

Now comes the installation of weatherstripping. Install weatherstripping all-around your air conditioner unit. Be assured that you use weatherstripping in the space between the top rail and the frame’s bottom and between the windowpane and the bottom of the air conditioner.

You may need to squeeze the weatherstripping into its place, but it depends on how tight the space is. 

Some Useful Tips To Properly Install Your Window Air Conditioner In A Sideways Window

1. Decide if you want to move/ tilt the window air conditioner.

In that case, it completely depends on the model of the air conditioner. So you can check it before you purchase it.

2. Weight dividing.

Once you are done with placing the bottom of the AC on the windowsill, make sure that the weight of the unit is equally distributed. 

3. Install the proper size.

When it is about a window air conditioner, it needs to be efficient as well as effective and correct in terms of size. 

4. Take help while installing the window air conditioner. 

Because it weighs around 50 to 100 pounds. So, it is heavy to lift up on your own. That is why it would be wise to take help from a partner. 


Window air conditioners are very effective and reasonable in prices to keep your space cool. But here is a reminder, if you live in a rented place or apartment, then you may have to ask for the landlord’s permission before you install the window air conditioner.

Installing a window air conditioner in a slideway window is not that complex and complicated. Above, I have given a step-by-step guideline on how you can install a window air conditioner in a sideway window. I hope this will work for you.

My final suggestion for you would be to check the AC unit’s manual for the instructions to install it, before you purchase it. Because those can be more specific to the specific model you want to purchase or have already purchased. Good luck, and thank you for reading this article.

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