Written by Tim denHartog 10:08 pm Answers and Analysis Q&A

Answers & Analysis | Summer 2022

Taken from the Online Editions of the UPC & UMC Answers & Analysis

SUBJECT: Rain Gutter Design
SECTION: Table 1106.3 (2015 UPC)

Question: According to Table 1106.3, the minimum slope allowed for gutters is 1/16 inch per foot. Does this mean that residential gutters with a lip that rests on the roof sheathing resulting in a completely flat trough would not comply with this requirement, or that any gutter installed without the 1/16 inch per foot minimum slope would not comply with this requirement?

Answer: Table 1106.3 cites standard theoretical carrying capacities of semicircular gutters, predicated on specific diameters and slopes. Application of accepted construction criteria is obviously necessary in mandatory rainwater drainage installations where damage from overflow or flooding could be critical. The purpose of Chapter 11, however, as stated in its first paragraph, is to provide design and installation guidelines only “where it is necessary to collect storm water and deliver it to an approved point of disposal.” The conditions of necessity and control are not established by the chapter as they are dependent on local factors and subject to local regulation. Since residential gutters are somewhat optional, a considerable degree of design latitude has traditionally prevailed where architectural conditions made sloping gutters impractical or unsightly.

SUBJECT: Appliance Connection
SECTION: Table 1208.4.1 (2015 UPC)

Question: Table 1208.4.1 no longer has a listing for a gas log lighter. Is the 25,000 Btu/H input rating for a gas log lighter still applicable as listed in UPC Table 12-1?

Answer: In older editions of the UPC, most of the language of Chapter 12 was imported from NFPA 54 and as a result some of the old code language was omitted. The Btu/h ratings shown in Table 12-1 (2003/2006/2009), Table 1208.4.1 (2012/2015) are generic figures and should only be utilized in the event that the actual Btu/h ratings for specific appliances are not provided by the manufacturer of the product. In the event that the Btu/h rating cannot be acquired from the manufacturer, the authority having jurisdiction may choose to approve a generic rating from a reliable source.

SUBJECT: Minimum Conveying Velocities
SECTION: Table 5-1.0 (2009 UMC)

Question: Table 5-1 minimum conveying velocities noting that velocities for aluminum and magnesium powder shall not be less than 4000 FPM. Is this minimum conveying velocity applied also to chemical product with aluminum or magnesium components such as aluminum starch, aluminum starch octenylsucciante, magnesium sulfate and magnesium sulfate heptahydrate? Is this pure aluminum and magnesium powder or it is applicable to any powder where aluminum and magnesium are components of that powder?

Answer: No, the specific chemicals listed are generally classified as stable, nonflammable and hygroscopic. If the authority having jurisdiction determines the products exhausted are comprised of combustible particulates where aluminum and magnesium are components of that powder, then the product conveying duct would need to maintain a velocity at least 4,000 FPM.

SUBJECT: Reduction of Clearances
SECTION: Table 5-3.0 (2009 UMC)

Question: Can the 2003 UMC Table 5-3 be used to reduce the side and rear clearances on a listed wood burning room heater? This is for the stove, not the vent.

Answer: No, the scope of Chapter 5 does not cover room heaters. Chapter 5 of the 2003 UMC does partially address solid fuel cooking appliances (e.g. wood burning). Listed wood burning room heaters shall be installed in accordance with building code, their listings and the manufacturer’s instructions. The 2003 UMC does include provisions for gas utilization type room heaters. A listed gas utilization type room heater would have to comply with section 924.3.

Last modified: May 8, 2024