I made my first soffit this weekend and I thought I would go ahead and post a guide on how I did it, since I have never done anything like this before. Feel free to tear me apart or, if you are in a particularly good mood, post your compliments.

First things first. You need to decide how big your sofit needs to be. Here is a picture of my pre-soffit HVAC run.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158865&stc=1&d=1258827261

The HAV unit is an 8x8 square. I will refer to the edges of the soffit the same way we talk about steps. The edges are Rise (how far down form the ceiling) and Run (how far out form the wall it sticks). I knew I wanted my run a bit longer than my rise, so I decided that my rise would be 9.5" and my run would be 13". The 9.5" is a calculated number. 8" of those inches are for the HVAC unit, 1.5" is for a 2x2 furring strip. Now if you are smart, you should immediately be saying, isn't that cutting it close. The answer is yes, BUT keep in mind, out HAT track from which we are hanging things gives you an additional 7/8" of headroom. I used this 7/8" as my "buffer" to account for the fact that the HVAC does sag a tiny bit in some places.

Plase keep in mind I used 1/2" OSB, so if you use something different, you will need to adjust from here on out. Also, keep in mind that some of the steps may seem out of order. I did things in the order I did, because some of the steps require 2 people, so I did as much of the prep work as possible by myself ahead of time.

Step 1
Using some 8x4 sheets of OSB, cut stips that are 9.5 inches. Measure the wall this soffit is running along (generally 15-25') and cut that much OSB.

Step 2
Cut/buy some 2x2 furring strips. (Obviously, these are actually 1.5" x 1.5", but I figured this is a newbie guide so I'd throw that in there.) Try and make sure they are as straight as possible. I ripped my own from 2x4's because Lowes 2x2 are anything but straight. Cut enough to run the whole room 3x. (Generally 15-25 feet x3.)

Step 3
Combine steps 1 and 2. Time to start screwing thigns together. Start by taking your 9" x 8' OSB and mark a line 8 feet long, 0.5" from the edge. Apply some Liquid nails to one side of your 8 foot furring strip and then attach the stip as show in the pic below. You can see we used the line at 0.5" to mark where the furring stip goes. This is a very important step. That 0.5" must be there for later. Combine all your OSB and furring stips from steps 1 and 2 in this manner.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158858&stc=1&d=1258826291

Step 4
Take your hat track that is going to be supporting the soffit and take it down if its already up. Lay down some scrap wood every few feet, perpendicular to the track. Lay the track as shown below. Run a bead of Liquid nails along the top of the track and then screw your furring strips to the HAT using 2" fine thread drywall screws.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158859&stc=1&d=1258826418

You will probably notice that your furring stip is bigger than the HAT track. I therefore, made sure to line up the furring strip so that one of the edges was flush. See pic below.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158860&stc=1&d=1258826443

Step 5
Attach the HAT to your clips. Notice how the flush side will allow you to easily attach the product from step 3.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158862&stc=1&d=1258826483

Step 6
We are now going to attach the product of Step 3 to our HAT + Furring as shown in the picture below. Notice how every thing lines up nice and neat. You will probably beed a 2nd person for this step.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158863&stc=1&d=1258826750

Here's how it looks in real life:
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158867&stc=1&d=1258827781


Step 7
This step is hard. It takes time time and you need to get it right. You now need to attach your last furring strip to the wall and its MUST be parallel as shown in the figure below.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158864&stc=1&d=1258826869

I basically measured 10 times and used a level in 8 different axises all to make sure things were even.

Here is what it looks like in real life:

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=158866&stc=1&d=1258827477

Step 8
Now just stuff the space with pink fluffy and put in your run piece (Which you have not cut until now because this is your last change to fudge things a bit!!!

I think I'm done. Feel free to critique.

Gelfling,

Thanks for sharing! It does really help people like me who are still in the design stage(4+ years design stage). Hahaha. :) Are the hat channels expensive? Are they really that strong? What type of screw is needed? What about the clips, how much were they and how much did you need?

I'm working on my family room right now and I also built a multilayered soffit/coffered ceiling. I just used a 2x2 wood. I know it's thin but I'm glad it came out really nice(in my own eyes, hehehe :p). We'll be priming it tonight and painting maybe tomorrow.

Thanks for sharing! I'll be able to use it in the future. ;)

Thanks for the post. I'm new to this, so it is definitely helpful.