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HomeAdvisor.com puts the cost of brick repair nationwide at roughly $1,300 to $2,000, with some repairs costing close to $4,000. Smaller brick repair jobs, such as repairing cracks in 10 or fewer bricks, often costs less than $500. Hiring a professional for a full day of brick repair over several areas of the home might cost $750 to $1,000. Yes blocks do crack in extreme weather.i would take off render.put mesh on then render.never crack again.even if blockwork cracked. 2018-08-12T19:30:02+01:00 Answered 12th Aug 2018.

Concrete block or cinder block chimney cracks & damage: this article describes cracks in masonry block or concrete block chimneys and suggests possible causes and crack severity.

These articles on chimneys and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Cracked Concrete Block Chimneys

Cracked concrete block chimneys risk unsafe chimney flues, presenting fire and flue gas hazards in buildings


Both outdoors and indoors we may also see chimney cracks which could be due to chimney movement (introduced above) or due to compression loads or other chimney construction problems (photograph below).

Our photo (left) illustrates serious frost cracking damage in a concrete block (or masonry block or 'cinder block') chimney serving a home in upstate New York.

Notice that there is no rain cap and no chimney cap protecting this chimney against water intrusion - defects likely to lead to frost damage and an unsafe flue, especially in freezing climates.

Cracks in a masonry block chimney always deserve further investigation to identify the probable cause, to decide on the remedy and to evaluate the safety and function of the chimney.

We recommend that you have any cracked or damaged chimney thoroughly inspected by a professional, including an inspection of the integrity of the chimney flue and of any fireplaces or other attached heating systems.

Common Causes of Concrete Block ('cinder block') Chimney Cracking

Our photo (left) illustrates a concrete block chimney suffering from both extensive cracking as well as spalling surfaces . We think there are leaks into the internal structure of this chimney, probably originating at the chimney cap.
See details at CHIMNEY SPALLING

It looks as if someone thought they might repair the chimney by coating its exterior with a masonry sealer paint or a thin stucco covering. But as leaks are originating from the chimney top and passing within the chimney structure, that repair did little good.

Cracks in a masonry chimney, particularly concrete block chimneys (this article) and perhaps brick may be caused by

  • chimney footing tipping or settlement (inadequate foundation) -
    see CHIMNEY LEANING, SEPARATION, MOVEMENT
  • expansive clay soil disturbing a chimney footing
  • frost (poor drainage, missing rain cap, porous masonry, improper construction in freezing climates) -
    see CHIMNEY CAP & CROWN DEFINITIONS
  • thermal expansion of the clay flue liner (improper construction, omission of an expansion joint at the chimney cap)
  • a chimney fire
  • mechanical damage or lack of adequate support for tall chimney sections -
    see BRACING for MASONRY CHIMNEYS
  • or perhaps other events such as earthquake -
    see EARTHQUAKE CHIMNEY COLLAPSE DANGERS

Readers should also see CHIMNEY INSPECTION FROM GROUND CHIMNEY CRACKS, SEPARATION, MOVEMENT.

Cracks in Masonry Chimneys May be Very Dangerous

Watch out: a chimney fire, even if it does not set the building ablaze, is likely to have caused serious damage to the chimney itself, leaving it unsafe, as may other chimney cracks or movements for any reason. The risks include building fires, potentially fatal flue gas leaks, improper draft, and unsafe heating equipment operation.

Our photo at left shows dangerous cracking indoors in a concrete block chimney used to vent a heating appliance.
You might also notice that the barometric damper is not level - a much simpler problem to correct.
As a chimney leans away from the house we might find several serious problems caused by that movement:

  • Damaged, unsafe chimney liner (flue gas leaks or sparks into the building interior, a fire or potentially fatal carbon monoxide hazard)
  • Damaged, unsafe fireplaces where the chimney has pulled the firebox away from the building or created dangerous openings around the fireplace into thebuilding structure, risking both sparks (and fire) or air leaks (and inabilityto control the draft).
  • Leaks into the building walls (flue gas leaks or sparks into the building interior, a fire or potentially fatal carbon monoxide hazard)

Unsafe fireplaces in the building: hearth cracks, fireplace side cracks, chimney damage all present risks of sparks or smoke entering the building cavities, a fire and flue gas risk. Check for evidence of movement at the fireplace. (Flue gas leaks or sparks into the building interior, a fire or potentially fatal carbon monoxide hazard)

Also see CHIMNEY CRACK DETECTION & DIAGNOSIS

Evidence of Prior Repairs May Indicate a History of Chimney Cracking & Movement in a Concrete Block Chimney

If you see repairs such as shown in the our photo (left) the chimney should be professionally inspected, especially to establish the condition of the flue liner as it may be unsafe.

Our pen points to a gap between masonry block chimney and a building wall, indicating chimney movement and raising question about other less obvious crack and damage to this structure.

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It may be possible to repair minor chimney racks with masonry products provided that the underlying cause is also identified and corrected.

Also, some concrete blocks may be cracked during their individual drying/curing process, a condition not to be confused with chimney cracking.

The usual repair when a significant chimney crack has occurred, damaging the chimney and the flue is to remove and replace the chimney, though in some cases it may be possibleto re-line the chimney and to jack an intact masonry chimney back to level and repair its connections into the building.

Repairs to Cracked Concete Block Chimneys

Extensive concrete block cracks, badly damaged masonry chimney flues, curved, leaning, broken masonry chimneys may need to be re-built to be safe and functional. But minor chimney damage, and chimney damage that is confined to just above the roof line can usually be repaired or re-built.

Watch out: be sure that the roof surface is protected from damage during rooftop chimney repairs, otherwise your chimney may be fixed but you could end up needing a new roof.

Also see CHIMNEY REPAIR METHODS.

Reader Comments & Q&A

Question: I was told that the building code in Massachusetts only allows block chimneys to be reparied with bricks

2017/04/26 Eddie Arroco said:

I need my fireplace chimney concrete blocks repaired or replaced above the roofline which are cracked and breaking up. I called in a contractor but I was told that the building code in Massachusetts only allow him to replace the blocks with bricks.

I'm afraid the bricks wihich is of different color will not look good at all. Is there any truth to this code since it is only a repair of existing structure? What do you suggest I should do? I would really appreciate your advise. Thank you very much.

Reply: Really? Ask again. Here are the Massachusetts Chimney Codes based on model building codes

I am really surprised at the claim that concrete block chimneys are not permitted in Massachusetts.

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And I'm doubtful. It might be that the mason wants to work with and use the materials with which she is most-comfortable.

But on occasion a builder speaks as if God told him the Truth when in fact he has never read even the instructions on the box of the device he's installing.

Take a look at these two Massachusetts chimney code documents and you will see that the words 'brick' or 'concrete block' do not appear anywhere in the code.

  • MASSACHUSETTS CHIMNEY CODE: Chapter 60, CHIMNEYS, FIREPLACES AND SOLID FUEL-BURNING APPLIANCES [PDF] - at inspectapedia.com/chimneys/Massachusetts-Chimney-Code.pdf

and

  • MASSACHUSETTS CHIMNEY CODE: 780 CMR 68.00 CHIMNEYS and VENTS [PDF] - at /chimneys/Massachusetts-Chimney-Vent-Code-780-CMR-6801.pdf

A modern concrete block chimney uses a hard-fired clay chimney liner inside the blocks and a listed or UL-listed approved chimney cap. You should not have to replace blocks with bricks.

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Now, call a chimney repair contractor or two in your area and let me know what they tell you.

While you're at it, have the entire flue interior inspected for safety too.

Question:

(Dec 18, 2012) chimney man said:

I just finished a blcok chimney with clay liner. 28 ft tall. i did it in cold weather but used a space heater.. days later to keep it warm i started a small kindling fire in the cleanout door..

half hour and let it go out. the next day i realized the block right above the cleanout door the mortar joint was cracked all the way around. the tile was not. and the thimbal is 4.5 feet about the cleanout. so heat wont touch that part from this point on once i get my stove in there.

i dont know why this happened. is it bad and what shuld i do?

(July 31, 2014) alan said:

I've got a question about a home that i saw on your web page, the picture shows the chimney in the back yard next to the deck and the house is tan with a brown roof. what kind of material is the outside of that chimney. It looks like some sort of vinyl paneling.

The reason i ask is because we have a brick fireplace that has been worked on 3 times over the last 15 years, we even had it torn down to the rooftop 8 years ago. Anyway, the inside of the chimney is solid per inspectiors, but the outside, even the newest part continues to pop and break

. I am looking for something new and cheaper to repair my chimney, would be nice to shore up the current chimney, and then put paneling around it. is this possible, and if so can you recommend a contractor in dayton ohio area that you work with? thanks for your help.

Reply:

Products

Alan, I don't see the photo you describe in the article above. But indeed some chimneys are constructed as an insulated metal flue run inside of a vertical wooden chase whose exterior is covered with a choice of siding materials.

Details are at

inspectapedia.com/chimneys/Wood_Chimney_Chase.htm

Note that this is NOT a way to repair a damaged masonry chimney if the flue is unsafe. But it MIGHT be possible to surround and cap a safe masonry flue with a new external chimney chase.

I'd be more tempted to simply stucco the chimney exterior of a spalling masonry instead.

On 2019-08-19 by (mod) - how to evaluate damage to a concrete block chimney

Jim
Evaluate the nature and extent of damage to a concrete block chimney:
I'd need to see some photos (one per comment) to make more specific suggestions, but if the damage is trivial a mortar patch compound would be ok.
There is much to ask first:
1. what kind of damage: cracking, leaning, spalling?
2. how extensive: small trivial areas or larger several inches or more of material loss
4. how serious: does the damage go all the way through the block or is it just superficial in depth
5. Safety concerns: is the damage caused by frost or movement that may also have damaged the flue liner making it unsafe?

On 2019-08-19 by Jim

How do I repair a deteriorating chimney block

On 2017-04-26 by (mod) - chimney repair codes for Massachusetts

Eddie,
I am really surprised at the claim that concrete block chimneys are not permitted in Massachusetts. And I'm doubtful. Way too often a builder speaks as if God told him the Truth when in fact he has never read even the instructions on the box of the device he's installing.
Take a look at these two Massachusetts chimney code documents and you will see that the words 'brick' or 'concrete block' do not appear anywhere in the code.
CHIMNEY CODE for MASSACHUSETTS http://inspectapedia.com/chimneys/Massachusetts-Chimney-Code.pdf
and

CHIMNEY VENTING CODE for MASSACHUSETTS
http://inspectapedia.com/chimneys/Massachusetts-Chimney-Vent-Code-780-CMR-6801.pdf
Now, call a chimney repair contractor or two in your area and let me know what they tell you.
While you're at it, have the entire flue interior inspected for safety too.

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On 2017-04-26 by Eddie Arroco - I was told that the building code in Massachusetts only allow to replace blocks with bricks

I need my fireplace chimney concrete blocks repaired or replaced above the roofline which are cracked and breaking up.

I called in a contractor but I was told that the building code in Massachusetts only allow him to replace the blocks with bricks. I'm afraid the bricks wihich is of different color will not look good at all.

Price

Is there any truth to this code since it is only a repair of existing structure?

What do you suggest I should do? I would really appreciate your advise. Thank you very much.


...

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Technical Reviewers & References

  • Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
  • John Cranor [Website: /www.house-whisperer.com ] is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-873-8534 or by Email: johncranor@verizon.net
  • Thanks to Luke Barnes for suggesting that we add text regarding the hazards of shared chimney flues. USMA - Sept. 2008.
  • Arlene Puentes [Website: www.octoberhome.com ] , an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at ap@octoberhome.com
  • Roger Hankeyis principal of Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com
  • NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
  • NFPA #211-3.1 1988 -Specific to chimneys, fireplaces, vents and solid fuel burning appliances.
  • NFPA # 54-7.1 1992 -Specific to venting of equipment with fan-assisted combustion systems.
  • GAMA -Gas Appliance Manufacturers' Association has prepared venting tables forCategory I draft hood equipped central furnaces as well as fan-assistedcombustion system central furnaces.
  • National Fuel Gas Code, an American National Standard, 4th ed. 1988 (newer edition is available) Secretariats, American Gas Association (AGA), 1515 Wilson Blvd., Arlington VA22209, and National Fire Protection Association (NFPA), Batterymarch Park, Quincy MA 02269. ANSI Z223.1-1988 - NFPA 54-1988. WARNING: be sure to check clearances and other safety guidelines in the latest edition of these standards.
  • Fire Inspector Guidebook, A Correlation of Fire Safety Requirements Contained in the 1987 BOCA National Codes, (newer edition available), Building Officials and Code Administrators International, Inc. (BOCA), Country Club HIlls, IL 60478 312-799-2300 4th ed. Note: this document is reissued every four years. Be sure to obtain the latest edition.
  • Uniform Mechanical Code - UMC 1991, Sec 913 (a.) Masonry Chimneys,refers to Chapters 23, 29, and 37 of the Building Code.
  • New York 1984 Uniform FirePrevention and Building Code, Article 10, Heating, Ventilating, and Air Conditioning Requirements
  • New York 1979 Uniform Fire Prevention & Building Code, The 'requirement' for 8' of solid masonry OR for use of a flue liner was listed in the One and Two Family Dwelling Code for New York, in 1979, in Chapter 9, Chimneys and Fireplaces, New York 1979Building and Fire Prevention Code:
  • 'Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep,' Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
  • Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
  • 'Rooftop View Turns to Darkness,' Martine Costello, Josh Kovner, New Haven Register, 12 May 1992 p. 11: Catherine Murphy was sunning on a building roof when a chimney collapsed; she fell into and was trapped inside the chimney until rescued by emergency workers.
  • 'Chimneys and Vents,' Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
  • 'Chimney Inspection Procedures & Codes,' Donald V. Cohen was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman, then editor/publisher of that publication. The production of the ASHI Technical Journal and future editions was cancelled by ASHI President Patrick Porzio. Some of the content of Mr. Cohen's original submission has been included in this more complete chimney inspection article: InspectAPedia.com/chimneys/Chimney_Inspection_Repair.php. Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
  • Natural Gas Weekly Update: http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp Official Energy Statistics from the U.S. Government
  • US Energy Administration: Electrical Energy Costs http://www.eia.doe.gov/fuelelectric.html

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

  • Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
  • Ceramic Roofware, Hans Van Lemmen, Shire Library, 2008, ISBN-13: 978-0747805694 - Brick chimneys, chimney-pots and roof and ridge tiles have been a feature of the roofs of a wide range of buildings since the late Middle Ages. In the first instance this ceramic roofware was functional - to make the roof weatherproof and to provide an outlet for smoke - but it could also be very decorative.
    The practical and ornamental aspects of ceramic roofware can still be seen throughout Britain, particularly on buildings of the Victorian and Edwardian periods. Not only do these often have ornate chimneys and roof tiles but they may also feature ornamental sculptures or highly decorative gable ends. This book charts the history of ceramic roofware from the Middle Ages to the present day, highlighting both practical and decorative applications, and giving information about manufacturers and on the styles and techniques of production and decoration.
    Hans van Lemmen is an established author on the history of tiles and has lectured on the subject in Britain and elsewhere. He is founder member and presently publications editor of the British Tiles and Architectural Ceramics Society.
  • Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
  • Chimney & Stack Inspection Guidelines, American Society of Civil Engineers, 2003 - These guidelines address the inspection of chimneys and stacks. Each guideline assists owners in determining what level of inspection is appropriate to a particular chimney and provides common criteria so that all parties involved have a clear understanding of the scope of the inspection and the end product required. Each chimney or stack is a unique structure, subject to both aggressive operating and natural environments, and degradation over time. Such degradation may be managed via a prudent inspection program followed by maintenance work on any equipment or structure determined to be in need of attention. Sample inspection report specifications, sample field inspection data forms, and an example of a developed plan of a concrete chimney are included in the guidelines. This book provides a valuable guidance tool for chimney and stack inspections and also offers a set of references for these particular inspections.
  • Fireplaces, a Practical Design Guide, Jane Gitlin
  • Fireplaces, Friend or Foe, Robert D. Mayo
  • NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
  • Principles of Home Inspection: Chimneys & Wood Heating, in (Principles of Home Inspection), Carson Dunlop, Associates, Toronto, Ontario
  • NFPA 211 - 3-1.10 - Relining guide for chimneys
  • NFPA 211 - 3-2 - Construction of Masonry Chimneys
  • NFPA 211 - 3-3 - Termination Height for chimneys
  • NFPA 211 - 3-4 - Clearance from Combustible Material
  • NFPA 54 - 7-1 - Venting of Equipment into chimneys
  • Brick Institute of America - Flashing Chimneys
    Brick Institute of America - Proper Chimney Crowns
    Brick Institute of America - Moisture Resistance of Brick
  • American Gas Association - New Vent Sizing Tables
  • Chimney Safety Institute of America - Chimney Fires: Causes, Effects, Evaluation
  • National Chimney Sweep Guild - Yellow Pages of Suppliers
  • ...
  • Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. The firm provides professional HOME INSPECTION SERVICES and also extensive HOME INSPECTION EDUCATION and home inspection-related PUBLICATIONS. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
    Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
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  • The HOME REFERENCE BOOK - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
    Special Offer    : For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page 'Promo/Redemption' space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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