Single-Wall Metal Vents and Chimneys: Inspection, Diagnosis, Cleaning & Repairs

Single wall metal chimneys:

This article describes Single-Wall Metal Vents and Chimneys, their Inspection, Diagnosis, Cleaning & Repairs.

Single-Wall Metal Vents and Chimneys

The single wall metal fireplace chimney shown at page top and shown again at below left was installed in a solid masonry fireplace in the 1960's.

It can no longer be safely used because of the new second story construction in the left of the photo.

Below is the original construction (before the addition) showing that the chimney had good clearance above the original building rooftop.

But as you can see below, a second story building addition constructed close to the original single wall metal chimney labeled B has left it too close to the new structure. In comparison, chimney A is an insulated metal chimney that extends more than two feet above the second story addition's rooftop.

NFPA 211: single-wall pipe is not allowed for "chimneys" of one- or two-family dwellings, although may be used as connectors, i.e., between the appliance and the chimney, provided it is NOT "galvanized steel pipe" for a solid-fuel-burning appliance connector. NFPA 211:12.4.1.2

This chimney will need to be replaced with a modern insulated flue and extended in height. As long as the fireplace is not used, that corrective measure can be deferred.

Shown below at a different building this metal chimney is not a Type B gas vent and may be unsafe.

Certainly it should not be in use for venting a heating appliance, not to mention the askew "cap" that appears to be blocking the actual venting of gases.

Do not mistake this single-walled vent for a Type-L vent nor for a Type-B vent even though a hasty glance may make it look like one of those.

This vent appears to be single-walled aluminum and it has what looks almost like a coffee can installed as a rain cap.

If the metal chimney we see in this photo is being used to "vent" a water heater it is probably not working and probably lacks adequate draft. The result may be carbon monoxide release in the building.

The very tall single wall metal chimney shown below is located on a building in Manhattan and was photographed from the Lotus Club. Several stories tall you can see that the chimney is braced about every 12-feet, and is askew, loose, and rusty.

This chimney was so tall I could not photograph the entire structure in one image.

As a single walled chimney in a cold climate venting gas fired equipment, one might question its venting efficacy. In turn, condensation from poor venting might be a factor in that rusting.

Below: a single-walled metal flue extending through the wall of a barn that has been converted to a welding shop and sales facility on Highway 61 north of Duluth, Minnesota.

Single-wall metal pipes used to connect heating appliances to chimneys (metal or masonry) are discussed separately

at FIRE CLEARANCES, SINGLE WALL METAL FLUES & VENTS 

where we provide details about single wall metal flues and their fire clearance requirements.

Single wall metal pipes are also described in our table listing clearances by gas-fired appliance type

at TYPE B-VENT CHIMNEYS - Listed Flue Vent Connectors for Gas Fired Heating Appliances.

Also see METAL CHIMNEY SAFETY ALERT - CPSC Document #5047.

Readers of this section should also be sure to review details

at FLUE VENT CONNECTORS, HEATING EQUIPMENT.

The remarkable single walled metal chimney shown at below-left was constructed using a "found" hollow aluminum electric lighting pole and is discussed by NHFireBear

at CHIMNEY TYPES & MATERIALS

Dangerous Modifications to Single Wall Metal Chimneys & Flues

Handrail Passing Through the Metal Flue

Above: at this single wall metal chimney installed at a restaurant in Oxaca, Mexico, we noticed that the chimney installer and the handrail installer simply could not find an accord.

Shown below in a closer look, the handrailing passes right through the chimney. Both the handrail and the chimney are unsafe.

For handrailing enthusiasts

see HANDRAIL CONTINUITY

...

Continue reading at FIRE CLEARANCES INDOORS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CHIMNEY HEIGHT & CLEARANCE CODE
• FIRE CLEARANCES, SINGLE WALL METAL FLUES & VENTS
• FLUE VENT CONNECTORS, HEATING EQUIPMENT
• METAL CHIMNEY CONNECTIONS - home

Suggested citation for this web page

SINGLE WALL METAL VENTS & CHIMNEYS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to CHIMNEYS & FLUES

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Questions & answers or comments about single wall metal chimneys & flues: installation, fire clearances, troubleshooting, maintenance.

	HOME	ABOUT	ASK a QUESTION	CONTACT	CONTENT USE POLICY	DESCRIPTION	POLICIES	PRINT	PRIVACY
	© 2026 - 1985 Publisher InspectApedia.com - Daniel Friedman