# Grease duct shaft? IMC 506.3.11



## steveray (Jun 12, 2019)

Who is calling this on a drop acoustical ceiling in a commercial kitchen? Commentary isn't a lot of help...Thanks!

506.3.11 Grease duct enclosures. A grease duct serving a
Type I hood that penetrates a ceiling, wall, floor or any concealed
spaces shall be enclosed from the point of penetration
to the outlet terminal. A duct shall penetrate exterior walls
only at locations where unprotected openings are permitted
by the International Building Code. The duct enclosure shall
serve a single grease duct and shall not contain other ducts,
piping or wiring systems. Duct enclosures shall be either
field-applied or factory-built. Duct enclosures shall have a
fire-resistance rating of not less than that of the assembly
penetrated and not less than 1 hour. Duct enclosures shall be
as prescribed by Section 506.3.11.1, 506.3.11.2 or
506.3.11.3.


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## cda (Jun 12, 2019)

Normally we see the wrap used.

Normally the duct is wrapped from the vent a hood through the roof. Normally I do not see any exposed duct below the ceiling. 

So is your question, should the wrap start at the drop ceiling,,

Or above it,,

Or below it?


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## steveray (Jun 13, 2019)

I was thinking  "AT"....as it has penetrated a "ceiling"......The wrap helps the clearances to combustibles typically, just wondering if this intent is hard ceilings or any "concealed" space....


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## cda (Jun 13, 2019)

I think I would require either the entire length to be wrapped or six inches to a foot below the ceiling, for the wrap to start.


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## mtlogcabin (Jun 13, 2019)

Start at the ceiling. Install non combustible materials 18" around the duct. Gypsum board ceiling tile for lay in ceilings.


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## steveray (Jun 13, 2019)

Details suck on the plans...SURPRISE!....They show the wrap coming down some arbitrary distance from the roof deck, but not the dropped ceiling...


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## rgrace (Jun 17, 2019)

steveray said:


> Who is calling this on a drop acoustical ceiling in a commercial kitchen? Commentary isn't a lot of help...Thanks!



IMO, if a grease duct penetrates a ceiling, a rated enclosure must be installed. The enclosure starts at the ceiling penetration and ends at the outlet terminal. "Ceiling" is generic enough to include a gypsum board ceiling or an acoustical ceiling tile system or any other method for constructing a "ceiling."

It looks like the language quoted in 506.3.11 above is from the 2009 IMC. A change to the 2012 IMC added "penetrates a ceiling, wall, floor *or any concealed space*". This change added a forth condition where a rated enclosure was required from point of penetration to outlet terminal. The 2015 IMC added "A *commercial kitchen* grease duct ..." in order to clarify that this did not apply to a residential kitchen grease duct.

I had a tenant plan once that contained a commercial kitchen. The tenant did not have a ceiling installed, only a rated concrete floor that separated the first floor from the second floor. This meant that all HVAC, electric, sprinkler system, grease duct, etc. was exposed. This was permitted by all the codes. The proposed grease duct installation included a side wall termination. This also was permitted, and met all the requirements for a side wall termination. Here's where the twist came in. Our Health Department does not permit commercial cooking operations without a ceiling being installed. I do not know the reason for this rule (perhaps worries about debris falling into the cooking operations), but the tenant had to install an acoustical tile ceiling over the area where cooking operations occurred, approximately 250 square feet of ceiling, in order to meet the Health Dept. requirement. The grease duct now penetrates a "ceiling". Would you require the rated enclosure due to the "ceiling" penetration? The amount of concealed grease duct was only that of 250 sq.ft. of ceiling. All the rest was exposed in the tenant space.


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## cda (Jun 17, 2019)

rgrace said:


> IMO, if a grease duct penetrates a ceiling, a rated enclosure must be installed. The enclosure starts at the ceiling penetration and ends at the outlet terminal. "Ceiling" is generic enough to include a gypsum board ceiling or an acoustical ceiling tile system or any other method for constructing a "ceiling."
> 
> It looks like the language quoted in 506.3.11 above is from the 2009 IMC. A change to the 2012 IMC added "penetrates a ceiling, wall, floor *or any concealed space*". This change added a forth condition where a rated enclosure was required from point of penetration to outlet terminal. The 2015 IMC added "A *commercial kitchen* grease duct ..." in order to clarify that this did not apply to a residential kitchen grease duct.
> 
> I had a tenant plan once that contained a commercial kitchen. The tenant did not have a ceiling installed, only a rated concrete floor that separated the first floor from the second floor. This meant that all HVAC, electric, sprinkler system, grease duct, etc. was exposed. This was permitted by all the codes. The proposed grease duct installation included a side wall termination. This also was permitted, and met all the requirements for a side wall termination. Here's where the twist came in. Our Health Department does not permit commercial cooking operations without a ceiling being installed. I do not know the reason for this rule (perhaps worries about debris falling into the cooking operations), but the tenant had to install an acoustical tile ceiling over the area where cooking operations occurred, approximately 250 square feet of ceiling, in order to meet the Health Dept. requirement. The grease duct now penetrates a "ceiling". Would you require the rated enclosure due to the "ceiling" penetration? The amount of concealed grease duct was only that of 250 sq.ft. of ceiling. All the rest was exposed in the tenant space.




A cleanable ceiling is easy to clean, and normally does not attract and capture dust.


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