Q&A on the combustible clearance specifications for single wall metal flues.

This article series describes the fire safety clearance distances required between oil and gas fired heating equipment and the nearest combustible surfaces.

FAQs: Fire Clearance for Single-Wall Metal Flue Vent Connectors

These questions & answers about fire clearance distances for gas-fired heating appliance flues. Indoor fire clearances for flues, vent connectors, and vents were posted originaly at FIRE CLEARANCES, SINGLE WALL METAL FLUES & VENTS - please be sure to check the distances given there.

On 2018-12-17 by (mod) - temperature above my gas fireplace reaches 400 F

Watch out hg: that sounds to me as if there may be a fire hazard - assuming that combustible wood framing is being heated so hot or hotter in the wall cavity.

You need an onsite inspection by a certified chimney sweep or chimney installer to review the type of chimney materials and required clearances as-built against the instructions given by the manufacturer of your gas fireplace.

Tell us the brand and model fireplace and if you don't already have a manual giving those clearances perhaps we can find one.

Also see PYROLYSIS EXPLAINED at https://inspectapedia.com/chimneys/Pyrolysis_Definition.php for more about possible fire hazards

On 2018-12-17 by hg

why temperature above my gas fireplace reaches 400 f degrees on the outside sheet rock and up to 18" from the top frame ? lack of insulation ?

On 2018-09-22 by (mod) - required fire clearance as well as the permissible materials

Patrick

The required fire clearance as well as the permissible materials around the flue depends on the type of chimney or flue:

the fuel being burned (wood, oil, gas), the chimney and surrounding construction material, the chimney type, it's fire-rating, and of course the manufacturer's specifications. So with apology, I am way too nervous to pretend I can give a correct reply when I don't know what we're discussing.

For example there are insulated double or triple-wall metal chimneys rated for "zero" fire clearance, or often a 1" clearance distance to combustibles. But other types of chimneys and vents will have different clearance distances.

On 2018-09-22 y Patrick Valentino

I am selling my home. Built in 85 in Texas. The inspector said that there was no firestop around the metal chimney flue. It is a one story home and I think he is talking about where the metal stack goes into the attic. It is open around the pipe/flue.

Looks to be about 12-18" of space all around the flue. I have lived here 20 years and have fires in the winter many times a season.

My question is, yes, I can add the metal square around the pipe and sheet rock the space so it is closed off, but could that have been designed this way and the inspector is now creating more of a hazard.

I understand safety and the cost is minimal, but something tells me the house was built this way and was inspected then and has been used for 33 years without incident. Please help. Want to do what is right but am concerned this is wrong to do. Thanks.

On 2017-12-15 by (mod) - can the flew pipe be smaller that the chimmey?

Yes, anonymous, if by flew pipe you refer to the metal pipe connecting the heating appliance to the chimney.

Watch out: if you are connecting a very small heating appliance like a gas fired water heater to a large old masonry chimney, the amount of heat produced by the heater may not be enough to get a draft going in the chimney.

In that case the risk is of backdrafting and unsafe heater operation, potentially producing fatal carbon monoxide.


Joe:

There is no expicit clearance distance given in model building codes for the distance between a pellet stove exhaust vent and a heating oil fill or vent pipe, though the manufacturer of your pellet stove will surely give safe clearance distances from various building features. Check there first.

There are general guidelines for oil filler and oil vent pipe clearances and termination locations:

Those are given at OIL FILL & VENT PIPING

On 2017-12-15 by Anonymous

can the flew pipe be smaller that the chimmey

On 2017-11-06 22:11:51.097665 by Joe

On the outside of the house. What is the minimum distance can a pellet stove vent be to the oil fill of my boiler?

On 2017-09-01 19:06:11.334587 by Teresa

Above

On 2017-07-22 by (mod) - fire-stop for B-Vens for Gas Chimneys

Brenda:

Where a metal chimney passes through building floors, ceilings, walls,

Most-common: if you are using a B-vent (typically a double-walled air-insulated vent for gas appliances, typically you'll see a fire clearance stamped right into the metal of the chimney, stating 1-inch MINIMUM clearance to combustibles - as you'll see in this photo

https://inspectapedia.com/chimneys/B-Vent_HaddonfieldNJ_Gill_182_DJFs.jpg

that's discussed at

TYPE B-VENT CHIMNEYS

and
TYPE B-VENT CHIMNEY FAQs

Possible: - if you are using a zero-clearance insulated chimney the product label usually rates it for zero clearance - or rated for in-contact with combustibles.

You do NOT and should NOT use a home-made insect screen to cover the fire clearance opening. Rather you should buy a UL-Listed (approved for fire safety) Type B Gas Vent collar and firestop such as shown in the photo of a MetalBest B-Vent Collar Fire Stop sold at Walmarts as I show above. .


and widely available from your heating and plumbing supplier, building supply stores, and even online at Walmart.

Keep in mind that a building permit and inspection is usually required for installing a heating appliance and its vent or chimney - something that you might think you won't enjoy but something should ask-for, since the inspection will improve the safety of your home.

On 2017-07-21 by Brenda Grant

For a flue pipe from a propane furnace how much clearance is needed as it goes through ceiling area? Can one put in metal mesh to prevent insects or critters from coming down from the attic?

On 2017-02-08 by Calvin

In NYS, using 6" piping from a wood stove, can I put a single wall 6" pipe through a 6 1/2" ID terracotta through-wall (with masonry around it)?

I had a stove there for years and want to reinstall one, however standards have changed.

On 2016-07-27 by (mod) -

Kim, what you describe is a bit non-standard, as well as giving only a partial idea of what is installed, leaving me unable to guess at what would be safe and proper. Ask for help from your local fire inspector or from a certified chimney sweep/installer.

On 2016-04-27 by kim

I'm under contract w/ the sale of my home, i have a double metal flu for gas water heater and gas furnace exhausting up through a double metal pipe through the sheet rocked ceiling there is a space apprx 1/4 inch around this pipe.

The buyers inspection says it is a fire hazard and wants it addressed, what is the proper spacing of this ?

On 2016-04-05 by (mod) -

Marc

Please use the page bottom CONTACT link to send me photos and I can comment further.

Typically you can handle closer-than-recommended clearance distances by one or both of:

- using insulated "zero clearance" metal chimney sections as the flue-vent connector between woodstove and chimney thimble

- adding properly-designed & vented heat shielding

On 2016-04-05 by Marc

xxx
I'm not sure if the link above will work but it's a picture of an extra flue in my basement.

The previous owner redid the basement up until about 6 inches from the flue.

Can I add a wood stove to this flue even though the flue is so close to the wall? I will have the required room from the sides and back of the stove once the extender would be connected but not sure if this is something I can do

On 2015-10-20 by Ray

How much space do you need between a gas fireplace chimney and wood studs?

Question: how high a chimney from the gas range

(Mar 7, 2014) Anonymous said: how high a chimney from the gas range

Reply:

Sorry anon I don't understand the question. A gas range is not normally connected to a building chimney.

...

Continue reading at FIRE CLEARANCES, SINGLE WALL METAL FLUES & VENTSor select a topic from closely-related articles below, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• B-VENT ROOFTOP CLEARANCE
• CHIMNEY CHASE CONSTRUCTION
• CHIMNEY CLEANOUT CLEARANCE to COMBUSTIBLES
• CHIMNEY CLEARANCE & CONDITION SAFETY
• CHIMNEY CREOSOTE FIRE HAZARDS
• CHIMNEY FIRE ACTION / PREVENTION
• CHIMNEY FLUE SEPARATION
• CONCEALED SPACE FIRE CODES
• FIRE-BLOCK Fire Retardant Foam Spray Building Insulation
• FIRE CLEARANCES INDOORS
• FIRE CLEARANCES, MASONRY CHIMNEYS
• FIRE CLEARANCES, METAL CHIMNEYS
• FIRE CLEARANCES, SINGLE WALL METAL FLUES & VENTS
• FIRE CLEARANCES WOOD & COAL STOVES
• FIRE RATINGS for ROOF SURFACES
• PYROLYSIS EXPLAINED

Suggested citation for this web page

FIRE CLEARANCES, SINGLE WALL METAL FLUES & VENTS FAQs 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 chimney fire clearance specifications & requirements for metal flues.

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Citations & References

In addition to any citations in the article above, a full list is available on request.

---

ADVERTISEMENT

---