# Hvac Rectangular Stack Inside Wall



## tk3000

Hello Folks, 

Recently, I started fixing and assembling ductwork inside the wall for the hvac. Some of the ductwork was simply missing, so I had to assemble entire rectangular ductwork out of 3.25"x10"x3ft half sections rectangular stack duct, s cleats, drive cleats, rectangular head (where the end forced vented grill will be present), stack boot (connecting the upper end of the stack to the ductwork in the attic). I also acquire the proper tools: bending/folding tools, snippets, etc.

The following pics depicts the assembling stages:






(part of the rectangular stack connected to the stack head, stack head has a flange that could be used to screw it to the bottom plate of the wall)
















(with connections made out of cleats and s-cleats, it is not a rigid structure, and was wondering if that is the way it is supposed to be?)

So, I was wondering if that is the right approach to fabricate these ductwork stacks. Should be cleat connections be taped with foil tape? Should the whole stack be wrapped  in reflectix insulation?

thks!


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## tk3000

Cont... (could only post so many images in one thread post)





(dry fitting on spot inside walls)

Last but not least, this is not a very rigid structure (the fabricate stack) to be rigidly erected inside the wall, and besides the flap present on the stack head at the bottom (which will be screwed to the bottom plate of the wall) there is nothing else supporting it; so, I was wondering what type of extra support -- if any -- should/could be added?

Also, whereon the upper boot connect to the ductwork in the attic above it seems that it just fits in there... should tape be added to better seal it (can not use sheet metal screws, not enough clearance)


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## Jeffh

YOu can add self-tapping sheet metal screws to the s-cleats about 2" in from either end, keep in mind you are going through about 5 layers of tin. This will give the wall stack duct some added rigidity as short drive cleats dont stiffen it up much. Wouldnt hurt to add foil tape to the joints.
You can add strappings(or a long 16" drive cleat) across each stud on other side, and screw it to the ductwork as well. That will secure it a bit better in place. 
Round connections should be fastened with at least 3 screws, but at least  one would be nice. Taping it wont hurt afterwards. 

Trim your drives down to a 1" fold over, you got like 2-3", makes it look shoddy.


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## beachguy005

If that's a return air duct, they usually just use the studs and wallboard on both sides as the air plenum, and not actual duct work.  If you are going to use it, when you attach it to the bottom you should raise it up high enough for baseboard trim to go under the grill.


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## buffalo

I think they sell a heavy guage strap that you would nail to the studs and then screw through into the duct to stiffen it . Is this a single story with duct in the attic ? I just used ceiling grills if that's the only reason your opening up the walls . 

  And the previous poster is right , looks a bit low . Figure your grill is going to have a 1" flange on it , what's the height of the baseboard?


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## tk3000

beachguy005 said:


> If that's a return air duct, they usually just use the studs and wallboard on both sides as the air plenum, and not actual duct work.  If you are going to use it, when you attach it to the bottom you should raise it up high enough for baseboard trim to go under the grill.



No, this is not an air duct return (I realize that they don't need an actual duct for returns). It is a force air duct. 

By raising the stack at the bottom you mean maybe adding a piece of 2x4 to that segment of the bottom sill?

thks


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## tk3000

buffalo said:


> I think they sell a heavy guage strap that you would nail to the studs and then screw through into the duct to stiffen it . Is this a single story with duct in the attic ? I just used ceiling grills if that's the only reason your opening up the walls .
> 
> And the previous poster is right , looks a bit low . Figure your grill is going to have a 1" flange on it , what's the height of the baseboard?



I will look into the heavy gauge straps, maybe once it screwed in place it will bee rigid enough. 

No, that is not  only reason: the drywall was damaged  so I would have to replace part of it anyways, besides I am also doing some electrical work along the way (albeit at a very slow pace lately)

The previous stack (or what was remaining of it) had it head stack attached directly and square onto the bottom sill plate, that why I was planning to attach it directly there. Would a piece of 2x4 atop of the sill plate be enough to raise the stack?

thks


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## buffalo

As far as height , what's the floor going to be ? Carpet / hardwood ect , and how deep will it be ? Figure your grill on the wall will be an inch lower than the square opening . How tall is your trim ? If it's to low you may be into the baseboard trim is all. 

I tried searching the Web quick and couldn't locate the straps . Basically it's a 1" strip of metal , just a heavy guage like 18guage.  

I personally like oval wall stack , easier than slip and drive .


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## nealtw

buffalo said:


> As far as height , what's the floor going to be ? Carpet / hardwood ect , and how deep will it be ? Figure your grill on the wall will be an inch lower than the square opening . How tall is your trim ? If it's to low you may be into the baseboard trim is all.
> 
> I tried searching the Web quick and couldn't locate the straps . Basically it's a 1" strip of metal , just a heavy guage like 18guage.
> 
> I personally like oval wall stack , easier than slip and drive .



Ovals are nice but every time I have had to work on them, I have had to get the boot made, nobody has a pattern for it..


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## nealtw

Fill the space between the studs and the boot at the bottom , screw the boot to it and you will have something to screw the grill to.

Just a flat piece of sheet metal long enough to reach both studs screw in place,

I like to lift them so the floor molding goes below.


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## Jeffh

Yes, a 2x4 near the bottem plate would work to raise the duct up. Id say about 4-6" to top of new 2x4 from finished floor height.


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## tk3000

buffalo said:


> As far as height , what's the floor going to be ? Carpet / hardwood ect , and how deep will it be ? Figure your grill on the wall will be an inch lower than the square opening . How tall is your trim ? If it's to low you may be into the baseboard trim is all.
> 
> I tried searching the Web quick and couldn't locate the straps . Basically it's a 1" strip of metal , just a heavy guage like 18guage.
> 
> I personally like oval wall stack , easier than slip and drive .



I am planning on installing ceramic tiles in the new future, and since it is a slab there would be no backerboard.  Baseboard: I don't know exactly but it should be basic type on the short size/side of the spectrum. 

I am also planning on wrapping the rectangular stack with reflectix type insulation. I saw some old one wrapped in a white (probably asbestos) type of thing.


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## tk3000

nealtw said:


> Fill the space between the studs and the boot at the bottom , screw the boot to it and you will have something to screw the grill to.
> 
> Just a flat piece of sheet metal long enough to reach both studs screw in place,
> 
> I like to lift them so the floor molding goes below.



By boot you mean the stack head where the register/grill will be attached to? How about the boot that connects to the ductwork above in the attic? I may not have enough room to screw it up there..

:thbup:


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## nealtw

Yes (I was talking about the bottom and higher up see what they did in this photo.
Or you can use plumbers strap.
https://www.homedepot.ca/en/home/p....el-24-gauge-34-inch-x-25-feet.1000115951.html


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## buffalo

nealtw said:


> Ovals are nice but every time I have had to work on them, I have had to get the boot made, nobody has a pattern for it..



Hey friend ! Really , pretty common here . Not that I would buy from the depot , but ...http://m.homedepot.com/p/SPEEDI-BOO...with-Adjustable-Hangers-SBH-6106-WS/202541987


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## buffalo

tk3000 said:


> I am planning on installing ceramic tiles in the new future, and since it is a slab there would be no backerboard.  Baseboard: I don't know exactly but it should be basic type on the short size/side of the spectrum.
> 
> I am also planning on wrapping the rectangular stack with reflectix type insulation. I saw some old one wrapped in a white (probably asbestos) type of thing.



HMM , tile up the wall? This is where I look to the pros of other trades . But to keep it simple , if the grill is not going to hit anything , your good .:rofl:


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## nealtw

buffalo said:


> Hey friend ! Really , pretty common here . Not that I would buy from the depot , but ...http://m.homedepot.com/p/SPEEDI-BOO...with-Adjustable-Hangers-SBH-6106-WS/202541987



It is a joke here, HVAC guys run the oval pipe down the wall and the stack head they install is a 6 x 6 x 10 box for the vent. Just had to find one a few months ago, had to send the sheet metal guy a drawing of what I wanted.
It is easier to run the rectangle down the wall with a flat cap on the bottom and just cut a hole for the grill.


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## buffalo

In that case your right , 10x easier . But then you need to duct it through the wall to the grill or else it blows into the wall . Not sure if that would cause a problem blowing any air into the wall cavity?


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## nealtw

buffalo said:


> In that case your right , 10x easier . But then you need to duct it through the wall to the grill or else it blows into the wall . Not sure if that would cause a problem blowing any air into the wall cavity?



Nope fits tight to drywall, wrap the joint between dry wall and metal with tape.
Cover with grill. I do cap the bottom of the 10x.


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## tk3000

buffalo said:


> HMM , tile up the wall? This is where I look to the pros of other trades . But to keep it simple , if the grill is not going tpo hit anything , your good .:rofl:



The difficult part in this case it removed the old flooring and its remanants (adhesives, black mastic, etc) in order to have a proper substrate for the thinset to adhere to. But the tiles are not going up to the wall

As far as baseboard, on a second thought it seems that instead of accounting for its height of baseboard   to simply eliminate the baseboard from under the grill. But I wlll make sure to pay attention to the clearance needed for the grill in any case, better be safe than sorry...


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## tk3000

Was a little bit too cold here lately, so I suspended activities; but weather is improving so backing to work... I got the hvac rectangular stack taped on its joints with foil tape and used one sheet metal screw to afix  a cleat that was protruding. After that I wrapped two sections of reflectixe insulation on the stack (one is loose and needs to be tapped), as shown below: 







I dry fitted the register at the bottom to have an idea of how it would fit and look, and in this case there no extra 2x4 piece atop of the bottom plate but still the bottom of the register front cover is way above the subfloor/slab and I wish I could get it flush with the floor. So the idea would be to not use baseboard right below the register and have it flush with the floor (new floor would raise subfloor by less than 1/2"). Would there other registers with different front face sizes or other easy way to fix this?

thks


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## beachguy005

Easy way to fix it?  Yes, raise it up 6".  As mentioned earlier, you're going to have issues when you install the baseboard trim.  That low and you'll have to butt cut ends of the baseboard against the grill.  Raise it up and the baseboard runs uncut below it.  It will also look better raised up.


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## nealtw

Or trim it out like you had a plan.


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## KULTULZ

nealtw said:


> Ovals are nice but every time I have had to work on them, I have had to get the boot made, nobody has a pattern for it..



You mean register boot?


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## nealtw

KULTULZ said:


> You mean register boot?



Yup that is one I have seen, if it made for a wall why does it have a 3" reach thru the drywall.. Not to many ceiling or floors that need an oval duct.


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## KULTULZ

Please bear with me Neal as you are the professional and I am the first year apprentice.

I was framing a partition wall a few years ago and decided to move the outlet register from ceiling to wall. I researched/ciphered and what I found is that oval takes less room in the cavity and is easier to work with. So I am just trying to pick your brain here... 

How about this design, is it better for his use?


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## nealtw

KULTULZ said:


> Please bear with me Neal as you are the professional and I am the first year apprentice.
> 
> I was framing a partition wall a few years ago and decided to move the outlet register from ceiling to wall. I researched/ciphered and what I found is that oval takes less room in the cavity and is easier to work with. So I am just trying to pick your brain here...
> 
> How about this design, is it better for his use?



I am no pro on this stuff but look at your photo, the oval is 3 1/2 deep and there is a half inch in the front where it can come thru the drywall, what are you supposed to do with the half inch in the back. 

I was told to strap out the wall a half inch and I said use a 4" round pipe.


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## KULTULZ

nealtw said:


> I am no pro on this stuff but look at your photo, the oval is 3 1/2 deep and there is a half inch in the front where it can come thru the drywall, what are you supposed to do with the half inch in the back.
> 
> I was told to strap out the wall a half inch and I said use a 4" round pipe.



If the boot is 3 1/2", that will account for the stud depth and the 1/2" for the drywall, right?

That register trim-out in the baseboard shown above is trick, I am going to borrow that...


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## nealtw

KULTULZ said:


> If the boot is 3 1/2", that will account for the stud depth and the 1/2" for the drywall, right?
> 
> That register trim-out in the baseboard shown above is trick, I am going to borrow that...



No, the duct is 3 1/2. the front sticks thru the drywall the back of the boots sticks out 1/2" where the drywall is supposed to go in the back.

What the problem is that the pros never put heat down a wall in the basement, they stay in the ceiling and this would fit in the outside wall because we build that 1" away from the concrete but then it gets no insulation behind it. The outside wall are all done when the house is built. So when a home owner want a room or two done they have Mr. Hvac run those down the wall and then a couple years later I am back to finish some more rooms, these have to be dealt with. Betyter yet is when they use one that has 6" deep boot for a 5 1/2 inch wall in a 2x4 wall, that I really don't understand.


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## buffalo

nealtw said:


> I am no pro on this stuff but look at your photo, the oval is 3 1/2 deep and there is a half inch in the front where it can come thru the drywall, what are you supposed to do with the half inch in the back.
> 
> I was told to strap out the wall a half inch and I said use a 4" round pipe.



That boot fits perfectly in a 2x4 wall . A 4" round pipe dosnt carry as much CFM ( cubic feet per minute ) . That's why they make oval pipe , it's equivalent  to 6" round .


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## nealtw

buffalo said:


> That boot fits perfectly in a 2x4 wall . A 4" round pipe dosnt carry as much CFM ( cubic feet per minute ) . That's why they make oval pipe , it's equivalent  to 6" round .



The oval pipe they use here is 3 1/2  thick, the boot is 4 1/2.
Yup 4" fit nicely in a 2x4 wall until you want to dry wall the back side.:rofl:


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## Jeffh

I think that boot needs dimensions written on it, before we can make assumptions on if it'd fit. I am able to get all sorts of sizes of oval, as I'm currently working with 42/20, 44/22 and 16/8.


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## nealtw

Jeffh said:


> I think that boot needs dimensions written on it, before we can make assumptions on if it'd fit. I am able to get all sorts of sizes of oval, as I'm currently working with 42/20, 44/22 and 16/8.



I am sure they are available but they just don't seem to be where I live.:trophy:


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## tk3000

beachguy005 said:


> Easy way to fix it?  Yes, raise it up 6".  As mentioned earlier, you're going to have issues when you install the baseboard trim.  That low and you'll have to butt cut ends of the baseboard against the grill.  Raise it up and the baseboard runs uncut below it.  It will also look better raised up.



Not sure if I can raise it that high without cutting the stack shorter: the duct work in the attic is in sort of fixed spot (I have to double check on that). 

I am also trying to depict how it is going to look asthetically. And it it looks better raises, I probably will go with it. 

thks


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## tk3000

nealtw said:


> Or trim it out like you had a plan.



Yep, that is an option too. Probably the easy way around!


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