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Jodie
Repair rusted duct boots w/o tearing up floor

We are looking to purchase a 45 yrold house. The ducts are located below the slab and there is no crawl space. A camera inspection showed that the ducts themselves are fine but the sides and bottom of the space between register and duct are rusted out. The suggestions I have received are 1.a concrete patch at the bottom of the boot; 2.a "liquid steel" or sheet metal patch on sides and bottom; 3.some kind of blown in plastic liner. We are hoping to not have to jack hammer the floor to fix the problem. Any suggestions? Is this a big enough problem that we should not buy the house?
Thanks

Sten
Re: Repair rusted duct boots w/o tearing up floor

Hard to say when so far away, can't see what the problem is, but if the boot is just rusting away I don't know why you would want to put a concrete patch in there unless the walls where the boot is located are deteriorating?? At any rate it doesn't sound like a major fix but like I said, can't see it.

ZZZ
Re: Repair rusted duct boots w/o tearing up floor

I would not attemp to repair this system. The only under slab duct systems I have seen all had problems with failed insulation due to water, mold, and rusted out metal. If the boot is in the poured concrete without insulation, you will not lose air through the holes, just efficiency through conduction of heat, which you would have anyway.
I would plan on another system entirely unless you want high utility bills and the possibility of mold remediation. I remember one system under a basement floor that would fill up with water when the sump pump failed and it sounded just like a washing machine when the fan came on.

Sten
Re: Repair rusted duct boots w/o tearing up floor
ZZZ wrote:

I would not attemp to repair this system. The only under slab duct systems I have seen all had problems with failed insulation due to water, mold, and rusted out metal. If the boot is in the poured concrete without insulation, you will not lose air through the holes, just efficiency through conduction of heat, which you would have anyway.
I would plan on another system entirely unless you want high utility bills and the possibility of mold remediation. I remember one system under a basement floor that would fill up with water when the sump pump failed and it sounded just like a washing machine when the fan came on.

Why would someone put Ductwork under a Basement floor??? Slab Yes but Basement?? :confused:

ZZZ
Re: Repair rusted duct boots w/o tearing up floor
Sten wrote:

Why would someone put Ductwork under a Basement floor??? Slab Yes but Basement?? :confused:

I wouldn't want them under the slab myself, but the one under the basement was in a university library built in 1965. It had a large air handler with the return air ducts entering the bottom. The work order I had stated that there was a sound like a giant washing machine throughout the basement. That same school built a preforming arts center with a huge multi story lobby. It had a 60" dia. round duct under the slab which also filled with water when the sump pumps failed. You would have to ask the architects why.

Sten
Re: Repair rusted duct boots w/o tearing up floor
ZZZ wrote:

I wouldn't want them under the slab myself, but the one under the basement was in a university library built in 1965. It had a large air handler with the return air ducts entering the bottom. The work order I had stated that there was a sound like a giant washing machine throughout the basement. That same school built a preforming arts center with a huge multi story lobby. It had a 60" dia. round duct under the slab which also filled with water when the sump pumps failed. You would have to ask the architects why.

Now you know why Architects have bigger erasers than most, seems like this one didn't use his enough ;)

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