Thread: HVAC ducting on the Ground in a sub area

I inspected a modular home with the HVAC ducting laying on the ground. I noted that most manufacturers install guidelines call for them to be off the ground due to potential moisture damage etc.
I am being questioned on this and besides noting possible damage is there anything else I can tell the client.

Norm

Similar Threads:

• Ground in crawlspace
• new HVAC techs among us
• Window in combo bath/shower area
• Kitchen area GFCI
• Recalled Ladders for Above-Ground Pools

Originally Posted by Norm Peery

I inspected a modular home with the HVAC ducting laying on the ground. I noted that most manufacturers install guidelines call for them to be off the ground due to potential moisture damage etc.
I am being questioned on this and besides noting possible damage is there anything else I can tell the client.

Norm

Hi Norm.. It is required to be raised on newer homes.
I see it on a large % of double wides. I let them know about the moisture issue, and also tell them if there's a leak or another source of water under the home the excessive moisture will enter the home through the ducting and damage the particle wood flooring.

Norm,

From the 2006 IRC

M1601.2 Factory-made ducts. Factory made air ducts or duct material shall be approved for the use intended, and shall be installed in accordance with the manufacturer’s installation instructions.

M1601.3.5 Factory-made air ducts. Factory-made air ducts shall not be installed in or on the ground, in tile or metal pipe, or within masonry or concrete.

M1601.3.6 Duct separation. Ducts shall be installed with at least 4 inches (102 mm) separation from earth except where they meet the requirements of Section M1601.1.2

Jeff Euriech
Arizona Prime Property Inspection LLC
Peoria Arizona

Thanks, Fellow AZ. boys. My computer crashed yesterday and I had to steal my wife's for a quick moment. Didn't have time to do the proper research due to her need of the computer for her business.
Norm

...........I know of no home manufacturers that don't stipulate that cross-over ducting shall be installed so as not to be in direct ground contact. That said, most attempts to suspend the ducting creates more problems than it eliminates. In MHO the easiest (best) solution is to place rigid foam on treated 2X sleepers on the ground to support the duct. Of course lots of manufacturers now use in-floor crossovers so it's no longer an issue.......Greg

Norm, mold potential! Temperature differential where the duct touches the ground will allow condensation to collect and mold will grow.
That should shut her up

A number of potential problems exist all having moisture as the root cause.

Moisture can enter the duct over time and will enter the home and damage the sub-floor or other flooring members as was mentioned before. Moisture collecting in the ducts can also caused mold as was said before.

I am also thinking as the duct deteriorates (due to rusting) it may allow pests to enter the duct. You will also have heat loss from the deteriorated duct.

Mike.

You are correct in calling this out. HVAC code calls for the duct to be suspended or supported every 4 feet and not touch the ground. It will void warranty for improper installation. The installer was lazy or stupid or both. Don't back down you did the right thing.

Originally Posted by Bill Scott

HVAC code calls for the duct to be suspended or supported every 4 feet and not touch the ground.

Which code for which type of duct?

I suspect that flexible duct is being discussed as that is what is typically used for these installations and the requirements for supporting flexible duct are that it be supported within 18" of where the duct attaches to the metal collar, and before the bend of the duct bends coming off the attachment collar, then supported with a maximum spacing between supports of 5 feet with a maximum allowed sag between supports of 1/2" per foot between supports, which means the sag may be 1-1/2" between supports spaced 3 feet apart, 2" sag between supports spaced 4 feet apart, and a maximum of 2-1/2" sag between maximum spaced supports of 5 feet apart.

The flexible duct much be kept at least 4" above earth.

Hey Jerry you are right. But since most HVAC installers attach the supports to the floor joist and all of the modulars that I have inspected are built to IRC codes and generally have 16" OC spacing, you can't get there with five foot spacing unless the joists are 12" OC. Of course the installer could scab something on the joist to get the 5' spacing, but I don't think it would be worth their time to save a little bit of strapping material. I am not nor do I wish to be a litigation consultant, just an old FHA inspector that has been in and around the construction trades for 58 years and only trying to pass a long that knowledge as to what my fellow inspectors should expect to see in the real world as to what is common acceptable construction practices and what is not.

Originally Posted by Bill Scott

Hey Jerry you are right. But since most HVAC installers attach the supports to the floor joist and all of the modulars that I have inspected are built to IRC codes and generally have 16" OC spacing, you can't get there with five foot spacing unless the joists are 12" OC. Of course the installer could scab something on the joist to get the 5' spacing, but I don't think it would be worth their time to save a little bit of strapping material. I am not nor do I wish to be a litigation consultant, just an old FHA inspector that has been in and around the construction trades for 58 years and only trying to pass a long that knowledge as to what my fellow inspectors should expect to see in the real world as to what is common acceptable construction practices and what is not.

Bill,

The requirements is not "5 foot spacing" between supports, the requirement is "maximum 5 foot spacing" between supports, thus even with 16" o.c. joists there is no problem meeting the "maximum" 5 foot spacing as one could support the ducts every 16", every 32", or even every 48", the other limitation is the allowed sag is based on the distance between supports at 1/2" sag per foot between supports, which means that duct supported at 32" would be allowed a maximum sag of approximately 1-1/4" ... but who is measuring something like that ...

"common acceptable construction practices and what is not" SHOULD be within what the code and the manufacturers allow, otherwise the people who inspect those things (which includes home inspectors) SHOULD bring non-conforming items to the attention of others as that is about the only way to get "common acceptable construction practices" to be what they should be - "in compliance with the code" - which is only a "minimum" standard.

A "minimum" standard should not be difficult to meet, should it?

Jerry: You sound like some of those loan underwriters I have to deal with from time to time or an attorney. How do you have an "common acceptable construction practice" with out it meeting the "minimum" code. I am sure that you would agree that "acceptable" means meeting the "minimum" code. I did not mean to imply your reading of the code was incorrect nor do I want words put into my response that I did not write. Yes the duct must be supported where it comes from and goes into a collar and supported a maximum of a 5' distance and yes most floor joists will allow a 4' maximum spacing or 16" or 32". And YES that is what most inspectors should expect to see. If you don't see that then "red flag." Neither you or I or any inspector can change the "minimum" requirements of the code. No, I do not measure the "sag" between supports. If I can't see a 1 1/2" sag, I shouldn't be under there doing an inspection. Call out the sags on your report and go on and finish your job. As for the 4" clearance, from time to time you can not get that clearance of a 12" duct under a 12" I beam. If the ground is such that it can not be dug out and the duct is supported on either side of the I beam and not touching the ground, then for me it becomes a judgement call that I believe most inspectors would pass except for maybe a litigation specialist. Since about 95% of my practice deals with new construction on manufactured and modular housing, I have educated the dealers and contractors of what is expected and they comply. The contractors don't want call backs and the dealers want the deal closed so that they get paid. And I HATE reinspections. If dealers get to many they usually get new contractors.

Originally Posted by Bill Scott

As for the 4" clearance, from time to time you can not get that clearance of a 12" duct under a 12" I beam. If the ground is such that it can not be dug out and the duct is supported on either side of the I beam and not touching the ground, then for me it becomes a judgement call that I believe most inspectors would pass except for maybe a litigation specialist.

Bill,

So you are saying that *only* "a litigation specialist" has the sense to grasp that the problems *is not* that the duct is too large to fit below the beam and leave proper clearance, but that the problem *is* that whomever installed the home *did not provide sufficient space for the duct*?

Since about 95% of my practice deals with new construction on manufactured and modular housing, I have educated the dealers and contractors of what is expected and they comply.

Excellent! That means you have them taking what goes under the homes into consideration when installing the homes at a height sufficient to allow for all the systems to be installed beneath the homes and meet all the required clearances. By the way, 'digging out' below a duct is not an acceptable solution when a duct is laying on the ground, all that does is create a hole which can fill with water and make matters even worse.

Do they install those pre-made fiberglass steps? The 'old' style or the 'newer' style? The 'old' style typically has four 8" risers, the 'newer' style typically has five 7" risers (the 8" risers do not meet code).

Come on Jerry. If you have the required slope for drainage around the home you do not get water under the house. That's the whole idea and requirement and something that is checked everytime and is a required note on the inspection report by HUD. Not all pad sites are level on the longitudal or transverse axis of the house and the setup crew will generally split the difference and set the house. You don't always end up with the same clearance from end to end or side to side of the house. Most of the dirt contractors here will give you a 50x100 pad thats within 1" end to end and side to side so clearance for the set up crew is not a problem but sometimes, not often, there is a hump in the pad. I see this most often when there has been a previous sturcture (house) on the site. On a small town lot there is not a hell of a lot that you can do sometimes. By the way have you ever run a set up crew? I have.

In my neck of the woods, we do not use the fiberglass porch and steps. I think they look like crap anyway. We build wooden steps and decks to IRC Code. One of the dealers (Palm Harbor Homes) has started using what is called a residential set and when completed the home looks like it is 12" off the ground and has poured in place concrete steps and landing. It makes for one nice looking house and you can't tell the difference driving by over a conventional built home. And yes it is engineered and approved. Sure is nice crawling around on clean visqueen under the house doing the inspection.

Originally Posted by Bill Scott

Come on Jerry. If you have the required slope for drainage around the home you do not get water under the house.

So you are stating that the required slope is "always" there, and that there is no other manner which could allow water to collect there? Come on, Bill, you know better than that.

You don't always end up with the same clearance from end to end or side to side of the house. Most of the dirt contractors here will give you a 50x100 pad thats within 1" end to end and side to side so clearance for the set up crew is not a problem but sometimes, not often, there is a hump in the pad.

Bill, you are saying that it is okay to NOT HAVE the required clearance under the house for the duct work because of a raised hump area? A good inspector, and a good foreman in charge of the setup crew would ... SHOULD ... make sure that THE LEAST CLEARANCE AVAILABLE MEETS the clearances required for proper installation of all systems.

By the way have you ever run a set up crew? I have.

Nope, I have never run a setup crew, but ... I have run some setup crews off because they could not grasp the minimum requirements that their installation had to meet. If one cannot grasp the complexities of leaving at least 4" clearance below the ductwork to ground, then one should not be doing that work. Let's see, 12" duct, 4" clearance to earth, that means there needs to be AT LEAST 16" below the lowest frame member that the duct must go under, and that should not be a problem as most installation guides require 18" below the frame member (golly, that provides an extra 2" of clearance for that 12" duct ).

In my neck of the woods, we do not use the fiberglass porch and steps. I think they look like crap anyway.

I agree that "they look like crap anyway", but one should not disapprove something based on cosmetics and the way it "looks".

We build wooden steps and decks to IRC Code.

Most here will attempt to build wooden steps, some even attempt to build those steps to code ... those that are even aware there is a code ... I find it EXTREMELY RARE that the wood steps and decks meet code, or are even close to meeting code. You must have more capable contractors in your area than we have here.

Sure is nice crawling around on clean visqueen under the house doing the inspection.

Down here (in Florida) installing, lapping, and taping/sealing the moisture barrier beneath new mobile/manufactured homes is a requirement - one should never have to crawl in 'dirt', maybe on 'dirty plastic', but not on the 'dirt' itself. If one is crawling under a new mobile/manufactured home in 'dirt', then the installer did not do the installation properly and they get to do it all over again.

The Florida specifications allow a maximum of 1-1/2" wood shims, the installation manuals I have seen only allow for a maximum of 1" shim space (the most restrictive of the two applies, so the maximum shim space allowed is 1"), so why would an installer install shims to take up a 2" space? Happens all too often down here.