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Dryer duct joint connection methods

fatboy said:
I think there is mixing and mis-matching of systems. Are we talking about a clothes dryer exhaust, or a duct system. Different chapters, different requirements..............
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Unfortunately 1502.4.2 for residential dryers instead of enhancing the article with requirements, it references 1601.4.1 for other ducts.

another poor code article that ads confusion.

2012 IFGC

[M] 614.4 Exhaust installation.

Exhaust ducts for clothes dryers shall terminate on the outside of the building and shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination. Ducts shall not be connected or installed with sheet metal screws or other fasteners that will obstruct the flow. Clothes dryer exhaust ducts shall not be connected to a vent connector, vent or chimney. Clothes dryer exhaust ducts shall not extend into or through ducts or plenums.

Both should coincide with each other
 
In summary (refer to mtlogcabin post #18); 2012 IRC Section M1502.4.2 requires fasteners; the 2012 IMC, IFGC and 2009 Mechanical Exhaust and Fuel Gas for Dryers prohibits them.

2015 International Mechanical Code (IMC)

Section 504.6.2 was revised to allow domestic clothes dryer exhaust duct sections to be joined with screws or similar fasteners which do not protrude more than 1/8" into the inside of the duct. This section now coincides with the requirements in the IRC.

Source: http://m.nahb.org/fileUpload_details.aspx?contentID=194014

Yet still prohibited for gas dryers.



 
The 2012 code had a bit of a reversal. Where it previously prohibited mechanical fasteners, it now requires them.

2012 IRC-M1502.4.2 "Exhaust ducts shall be sealed in accordance with section M1604.4.1 and shall be mechanically fastened." (goes on to limit the screw protrusion into the duct to 1/8")

2009 IRC-M1502.4.2 "Ducts shall not be joined with screws or similar fasteners that protrude into the inside of the duct."

I can only assume they had some failures of duct joints using only tape or mastic, which the commentary indicates. We are skipping the 12 and adopting the 15 next, haven't read the 15 on this subject yet.
 
Sorry, just saw page two and realize my last post was already covered.
 
Thinking that a couple pop rivets or tiny sheet metal screws at each connection will be what I am requiring from here on out. Worried about dryer exhausts in concealed spaces falling apart with no one knowing.
 
Coder said:
Thinking that a couple pop rivets or tiny sheet metal screws at each connection will be what I am requiring from here on out. Worried about dryer exhausts in concealed spaces falling apart with no one knowing.
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I would be concerned that screws/rivets will catch lint and create a hairball the size of a cat. How will you know how far the screws/rivets project into the duct? If it is put together correctly, there should not be a way for it to fall apart.
 
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Cat size lint is already a problem.

It's an issue of length, and the dumbness of long vertical vents.

I would rather the design take it horizontally or down for a minimum run rather than up.

In my house every month I have to haul the weed blower into the upstairs laundry and blast all the crap out. I checked and it's just taped up, no fasteners.

While we are at codes, can we get upstairs laundry banned too, unless there is also a downstairs too?

Thank you in advance.

Brent
 
MASSDRIVER, LOL. The trend of laundry rooms upstairs surprised me the first time someone proposed it. The prospective homeowner (an old friend) pointed out that 90% or more of the laundry was generated upstairs - clothing, bedding - hence it was a convenience as opposed to schlepping the laundry down and then up stairs again. Actually makes sense and I've considered moving mine to the top floor.
 
JBI said:
MASSDRIVER, LOL. The trend of laundry rooms upstairs surprised me the first time someone proposed it. The prospective homeowner (an old friend) pointed out that 90% or more of the laundry was generated upstairs - clothing, bedding - hence it was a convenience as opposed to schlepping the laundry down and then up stairs again. Actually makes sense and I've considered moving mine to the top floor.
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Consider most of the time is spent on the main level and will be forced to make multiple trips to the upper level for the washing and drying cycles especially if doing several loads.

Then there's the joy of replacement and service.
 
2015 International Mechanical Code (IMC)

Section 504.6.2 was revised to allow domestic clothes dryer exhaust duct sections to be joined with screws or similar fasteners which do not protrude more than 1/8" into the inside of the duct. This section now coincides with the requirements in the IRC.

This is what I am thinking I can hang my hat on. Will be adopting the 2015 in a couple years anyways.
 
Coder said:
2015 International Mechanical Code (IMC) Section 504.6.2 was revised to allow domestic clothes dryer exhaust duct sections to be joined with screws or similar fasteners which do not protrude more than 1/8" into the inside of the duct. This section now coincides with the requirements in the IRC.

This is what I am thinking I can hang my hat on. Will be adopting the 2015 in a couple years anyways.
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I can hang my hat on
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the screw that sticks an inch into the duct.So then at each such inspection one must ask that a screw be removed. Then the victim will be informed that they have used the wrong screw. Debate will commence. Ridicule will ensue. Screw that.
 
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Francis Vineyard said:
Necessity being the mother of invention; could be a market for dryer duct seamless locking clips or buttons.
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How about metal hose clamps? I'm not fond of the screw method either ICE, but if it is allowed in the 2015 code then I guess it needs to be addressed (or amended out).
 
Coder said:
How about metal hose clamps? I'm not fond of the screw method either ICE, but if it is allowed in the 2015 code then I guess it needs to be addressed (or amended out).
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When it gets here it's gone. I reckon a zip tie and tape will suffice.
 
OK, new to this forum. Digging up an old post.
I am an HVAC designer, and we have always installed dryer venting in 4" galvanized steel pipe regardless of gas or electric appliance. We have also always taped the lapping joints with UL foil tape, then supported the exhaust piping every 4'. This has not been an issue until today when a state inspector says that we have to secure the pipe with screws or rivets 3 per joint. This references IMC 603.4.1 Now I contest that a dryer vent system is not a duct system, and that that rule does not supersede IMC 504.8.2 And on top of that the time involved in drilling holes and pop riveting or installing screws that small (which are very difficult to find in anything other than a phlips head) would add a lot to new construction jobs. Zip ties and hose clamps dont do anything to secure this type of piping either, so the code guys need to propose some realistic solutions.
 
Welcome to the board.

The code guy just needs to apply the correct section. BTW you UL foil tape is not listed for use on a dryer duct.

Chapter 6 is not applicable since domestic clothes dryer duct are specifically addressed in Chapter 5.

501.5 Ducts.
Where exhaust duct construction is not specified in this chapter, such construction shall comply with Chapter 6.

504.8 Domestic clothes dryer ducts.
Exhaust ducts for domestic clothes dryers shall conform to the requirements of Sections 504.8.1 through 504.8.6.

504.8.2 Duct installation.
Exhaust ducts shall be supported at 4-foot (1219 mm) intervals and secured in place. The insert end of the duct shall extend into the adjoining duct or fitting in the direction of airflow. Ducts shall not be joined with screws or similar fasteners that protrude more than 1/8 inch (3.2 mm) into the inside of the duct.

That pretty much eliminates screws since the taper end of the sheet metal screw is longer than 1/8 inch. As for using a 1/8" pop rivet with a crimped end joint connection, well good luck making that work.

 
The commentary for the IMC agrees with the state inspector about the fastening of dryer ducts with screws or rivets, stating that tape is for sealing, not fastening. It should be noted that the commentary is not code.
Wheelbaron said:
Now I contest that a dryer vent system is not a duct system, and that that rule does not supersede IMC 504.8.2
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I would tend to agree that the sections are different, and it would be rare for me to write that correction if things appear to be properly supported. If there is not strain on the joints, I personally have bigger fish to fry.
 
2021 IRC

M1502.4.2 Duct installation. Exhaust ducts shall be
supported at intervals not to exceed 12 feet (3658 mm)
and shall be secured in place. The insert end of the duct
shall extend into the adjoining duct or fitting in the direction
of airflow. Exhaust duct joints shall be sealed in
accordance with Section M1601.4.1 and shall be mechanically
fastened. Ducts shall not be joined with screws or
similar fasteners that protrude more than 1/8 inch (3.2 mm)
into the inside of the duct.
 
The IMC requirement is for support and secured in place every 4 ft. If you do both then a mechanical fastened requirement is overkill.
Maybe that is why that requirement is not in the IMC.
 
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