# Easiest, Cheapest, Best Butt Joint?



## meezike (Apr 8, 2015)

Hello, I am new. I want to build a simple but sturdy wood frame using 2X4s to support a window air conditioner that weighs about 70 lbs. It will be a square frame with a horizontal piece in the middle that will support most of the weight. Originally I was just going to just use 2 wood screws at each corner to make 90 degree angles, but them I started reading about all the other possible joints that exist. But, I only have very basic hand tools (e.g., saw, drill, jigsaw, circular saw, a few sawhorses, etc.) so I was wondering what would be the best way to do this with what I have? Would just using the screws be sufficient? Should I use glue? What about metal braces and brackets like these? This doesn't really have to be pretty, just safe. Thanks!


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## MT Stringer (Jul 21, 2009)

Is the frame going into an existing wall?


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## meezike (Apr 8, 2015)

Yes, it's going to go in an existing window opening. But the air conditioner is made for double hung windows and not the horizontal sliding type like we have, which is why we need to build some sort of a frame.


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## Steve Neul (Sep 2, 2011)

Actually a double hung window shouldn't be made to support an air conditioner. A supporting frame should be made anyway. I think a simpler solution would be to buy a supporting bracket made for that application. Then you don't have to paint or finish it to keep it from rotting. http://www.nationwide-products.com/ac-safe/products.html


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## meezike (Apr 8, 2015)

I looked at those but the only problem I had was that according to the installation instructions, it needs to be screwed onto the outside window sill. Our outside sill is pretty much flush with the wall so we can't screw it there. We have a sill on the inside but I wasn't sure if that would work. I sent an email to the manufacturer to ask if I can attach it there instead but they never replied.


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## MT Stringer (Jul 21, 2009)

Did you remove the window in it's entirety or are you planning to install the AC inside of the window frame? That wasn't clear to me in your original post.

Pictures of your planned window installation and make/model of the AC unit would help. 
What type of building is this going in to. Wall thickness?

The more info you can provide, the better the suggestions/advice will be.
Mike


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## Toolman50 (Mar 22, 2015)

Meezike
Build a simple 4 sided rectangle slightly larger than the outside dimensions of your A/C unit out of 2X4's. 
Use 3 1/4" screws to assemble. No glue needed. Screw this new frame into the window opening using 
3 1/4" screws. This will be very sufficient and outlast the window unit. Caulk around all cracks to seal the opening.


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## MT Stringer (Jul 21, 2009)

Following the Toolman's thoughts, here is my rendition of what you may be looking at. The drawing is generic and not to any scale.

The typical wall framing is colored to look like OSB. The window sill is in place, and your new frame is inserted in the opening.

Once you get the frame installed, you can trim it out as needed. Most likely you will need filler strips like I have shown so you can attach drywall or plywood or whatever you choose to cover the remaining part of the opening.

Hope this helps, and doesn't add to the confusion.
Mike


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## meezike (Apr 8, 2015)

Thanks guys. These sound similar to the directions I found here that I was looking at: http://www.instructables.com/id/Mounting-a-Standard-Air-Conditioner-in-a-Sliding-W/step6/Installation/
Is this what you recommend or are you suggesting to put the frame inside of the window frame as opposed to outside of it? Also, would it be best to pre-drill and use regular wood screws or would it be ok ro use self drilling screws without predrilling?


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## woodnthings (Jan 24, 2009)

*I've done this a few times myself*

The weight of the unit rests on the inner frame for the most part. It is supported at the rear by a metal bracket..usually. The brackets are adjustable for different lengths. You can make your own brackets from wood and some flat metal "L" brackets bent at the appropriate angles. OR you can make them from electrical thin wall tubing flattened at each end with a hole drilled for a bolt or screw.

A commercially made bracket:









The unit should be leveled out which may require a second set of hands to measure the length of the brackets. Here's how I do it: I remove the unit from it's metal case to get access and reduce the weight. Then I can work with the case, level it and have a access to the holes at the rear. Once the case is supported on it's brackets, slide the unit back in and fill in around it to seal it off. Most AC's will drain condensate either from a small hole or a hose running from that hole. The hose is best so you can control where it splashes.

You don't need some massive frame to support it. :no:


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