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Carpet at fireplace (C) Daniel Friedman Fireplace & Hearth Damage FAQs
Q&A on Inspection & Repair of Damaged Fireplaces & Hearths

Fireplaces & hearth damage, cracks, settlement, & other fire hazards:

This article describes masonry fireplace damage, cracks, settlement, and fire hazards and suggests inspection points and some repair procedures. We also link to other fireplace and chimney-fire safety articles and advice. At page top: our photo shows the collapse into the room of a poorly-secured wood frame around a masonry fireplace.

This article series provides information about masonry fireplaces, including inspection for damage/hazards (cracks and gaps that appear at masonry fireplaces due to chimney or fireplace settlement or movement), fireplace chimney sizing requirements, draft problems, chimney safety, creosote problems, inserts, and other topics.

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Q&A on Masonry Fireplace & Hearth Safety Hazards

Fireplace burned floor (C) Daniel FriedmanThese questions & answers about fireplace and hearth safety or damage assessment were posted originally at FIREPLACE DAMAGE & UNSAFE HEARTHS - be sure to review the dangers described there.

[Click to enlarge any image]

On 2020-01-16 by (mod) -

Kate that's an excellent up-close photo but I need some distance too as I have no idea what I'm looking-at.

Meanwhile: watch out: if you mean that the hearth, the fireproof extension over the building's floor in front of the fireplace, is being damaged by fires, there is a risk of setting the home on fire.

Watch out: Stop using the fireplace until this is sorted out. Else you could be risking a dangerous house fire.


Please also take a look at the hearth safety & inspection notes starting above at FIREPLACE DAMAGE & UNSAFE HEARTHS

On 2020-01-16 by Kate

Hi: Just moved into a place with a fireplace and have been making fires and the hearth is damaged as a result.

I've been keeping all the wood to the back of the fireplace so I'm not sure why this is happening or how to fix it. Thanks

On 2019-04-12 by (mod) - concrete back of the hearth is cracked

Kali

I can't assess the danger of the cracked fire back in your fireplace from just text - the issue ranges from cosmetic to a serious fire hazard depending on the materials and details of construction and the type, size, and location of the crack as well as its cause.

You would not buy a home without an expert home inspection - a good place to start is with the inspector's opinion.

Do not make the mistake of assuming that all building defects, even serious ones, will be classified as "code violation" nor that code compliance means you don't have important repairs needed at a property.

On 2019-04-12 by Kali

I'm in the process of buying a property that has a wood fireplace. The concrete back of the hearth is cracked. How dangerous is that, and could that be a city code violation?

On 2017-08-15 b by (mod) - fireplace that "sits on a wood floor" is a house fire waiting to happen

Sharon,

I may have misunderstood but your note scares me. A fireplace that "sits on a wood floor" is a house fire waiting to happen.

Cement may have fallen out for a variety of reasons such as floor movement or framing movement below, but if this were my home I would not consider using such a fireplace before having it inspected for safety by your local fire department or by a certified chimney sweep who has expertise in fireplace safety.

On 2017-08-15 by Sharon V.

I have a brick raised hearth fireplace. House was built in 1984. The bottom of the fireplace which sits on the wood floor, the cement around it on the bottom has pieces that have fallen apart over time.

What caused this and would I call a mason or chimney cleaning company? One of our floor planks are raised. I'm assuming this caused the raised plank.

On 2017-01-08 by (mod) - repair to bricks in the back of the fireplace

Patsy

That is a temporary repair indeed, but I am not sure it's safe. You are probably describing a factor-built fireplace insert that was UL listed for safety in its ORIGINAL DESIGN with a combination of metal backing, insulation, fire bricks, as well as specific clearances from nearby combustible framing.

When you modify such as system you scare the heck out of anybody you ask, the manufacturer, fire inspector, or me, because unless your hubby was a fireplace design engineer we don't think his design would be approved by any authority.

The hazard can be subtle: a spark through a crack, or even simply increased operating temperatures around the fireplace that eventually set the house on fire.

Search InspectApedia.com for PYROLYSIS EXPLAINED to read details.

Unless the fireplace manufacturer approves this repair it is not safe and you should not be using the fireplace.

On 2017-01-08 by Patsy

The back bricks inside our fireplace broke out. My husband covered the back with a panel of sheet metal, not galvanized. Is this safe? He said that because there is a metal box behind the bricks, a wall is not exposed.

On 2016-07-13 by (mod) - proper dimensions for a fireplace hearth

Thanks Manku. You're right - mostly.

The ICC specifies 16" hearth extension to front of the fireplace for fireplaces <6 sqft. and 20" hearth extension to front of fireplace for fireplaces = or larger than 6 sq.ft.
quoting:

R1001.10 hearth extension dimensions

Hearth extensions shall extend at least 16 inches (406 mm)in front of and at least 8 inches (203 mm) beyond each side of the fireplace opening. where the fireplace opening is 6 square feet (0.6 m2) or larger, the hearth extension shall extend at least 20 inches (508 mm) in front of and at least 12 inches (305 mm) beyond each side of the fireplace opening.

Here's another quote from a typical residential building code

(TB 21, residential building code masonry, chimneys and fireplaces - areas frequently misunderstood" allegany county division of permits and land development services residential information sheet # 21 revised january 14, 2003 )

There shall be a minimum distance of 36 inches from the back of the firebox to the end of the hearth extension. hearth extension shall extend at least 16 inches in front of, and 8 inches beyond each side of the fireplace opening.

When the fireplace opening is 6 sq. ft. or larger, the hearth extension shall extend at least 20 inches in front of, and 12 inches beyond, each side

On 2016-07-13 10:43:30.812729 by Manku

These days hearth extension is 16" inches minimum not 18" inches as mentioned in the sketch, am i right ?

Question: footings under additional fireplace hearth supports?

(Aug 14, 2011) Robert said:

When adding support brace under hearth should new footing be poured to support brace and weight

Reply:

Good question about hearth support, Robert.

If your floor slab is 4" or thicker, you should be OK with placing supporting columns below the hearth right onto the slab surface.

If the floor slab is thinner than 4", if it already shows signs of settlement, cracks, damage, the best repair is to cut a hole in the slab, excavate and pour a footing or pier for your columns, typically using a cardboard tube or form for the pier.

An alternative that I used in many building renovations of older homes where we needed to support an additional Lally column in a basement where the floor slab looked "OK" but was of unknown thickness, was to bed a solid 4" concrete block in concrete right onto the floor surface.

The block served as a footing or pier for the column and helped spread the load out onto a wider area than otherwise had we just put the Lally column base right onto the floor itself.

Question: heatilator not working after a chimney fire

(Nov 4, 2011) Jim Jackson said:

I had a chimney fire last wintwer and immediately putit out. After that I have noticed that the heatalator that is built in does not work...do I need an inspection and is it covered under my home owners insurance?

Reply:

Jim I don't know what your homeowner's policy covers - you'll need to call your insurance company to ask. But it makes sense to have an inspection of the system for two reasons

- the chimney may be very unsafe. Frankly, after a chimney fire I would never use that chimney again without first having an expert and thorough inspection of the entire assembly

- the damage, if traced to the fire, may be covered by insurance.

Question:

(Nov 21, 2012) Dee said:

I have a glass plate hearth on top of an oak floor and under my log burning stove. It is about 18 months old now.

Over the last few months the wood floor underneath the clear glass hearth has started to darken and grow mold. Now I have droplets of water under the glass and this is clearly where the mold is coming from.

What can be causing this? The rest of the wooden flooring is fine, with no mold or dampness even under rugs.

Reply:

Dee

I'm not sure where it's coming from, but if you are seeing mold growth there has to be a moisture source. Are you sure it's mold?

Question:

(Feb 23, 2013) KLynne said:
Inspection of the fire box in the house I am renting revealed cracks and chips.

The tech said they are small and adv I could burn occasional fires but not too much wood and no more than 2 hours.

Owner will not replace fire box. I don't want to use it at all due to the cracks and chips but was researching online and saw mention of fireclay mortar that can be used to repair a fire box. Is this a practical and safe way to repair the fire box and be able to use the fireplace?

(Apr 24, 2014) Roger said:
If the firebox is elevated 12" or more off the floor do you still need a non combustible hearth extension or con the hardwood flooring be installed up to the wall that the firebox is located in?

Reply:

Roger I don't have the full picture of your installation, but a general answer is yes you need a non-combustible hearth even for an elevated fireplace

Depending on the type of fireplace and fuel, at some height the worry about radiated heat damaging the floor would of course diminish, or fall to nil. There remain spark issues.

Question: safety of shared fireplace flues?

(Jan 24, 2015) Mary Siegel said:
Have a fireplace with 2 masonry flues. One serves a first floor wood burning fireplace and the second was built to serve a lower level wood burning fireplace.

Since we never used the lower level fireplace, we built an outdoor fireplace on the back side of the lower level place and used that flue to vent it.

Both the first floor and outside fireplaces work fine with this configuration. However, this year we decided to put a vent free log system in the lower level (closed off) fireplace. This fireplace had a damper with a space above it. Question: is there a way to vent our vent free logs to get rid of the gas smell. Could we install a vent that goes from the space above the damper to the outside?

I believe there is plenty of depth in the masonry to fit a vent but would that work and is this safe?

Reply:

Mary

Sharing a fireplace flue is asking for trouble in draft as well as raising safety and fire spread concerns (which is why it's a code violation).

For a gas fireplace insert you'll want to provide both combustion air and venting as per the manufacturer's specs.

You MIGHT be able to do that by building a direct vent to the outdoors for each purpose. I've done that using a small positive vent fan to assure no backdrafting. You'll be required to and should want to also ask for a building permit and inspections.


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