Metal Stitching Repair Process. The illustration of the Metalock Repair System (Metalocking), shown below, is a basic repair to a flat surface.Damage to more complex fractures and castings requires the Metalock Engineer to draw on his skills and knowledge in coping with both the difficulties of the component’s shape, its operation and its working environment. We also stock Thermalite products, including the Thermalight Shield Block, Coursing Brick, Hi-Strength Block and T&G Trench Block. Start your project off by building the right foundations and shop our range of concrete blocks in your local Selco store or online today.

• Thermalite Blocks Lowe's
• Repairing Cracks In Thermalite Blocks Prices
• Thermalite Products Inc
• Thermalite Lightweight Building Blocks
• Repairing Cracks In Thermalite Blocks Price Per Block

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Thermalite Blocks Lowe's

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.

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.

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.

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:

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.

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.

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.

...

Continue reading at CHIMNEY CRACK DIAGNOSIS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see BRICK CHIMNEY CRACKS & COLLAPSE

CHIMNEY INSPECTION DIAGNOSIS REPAIR - home

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CRACKED CHIMNEYS, MASONRY BLOCK at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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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.
  The ILLUSTRATED HOME illustrates construction details and building components, a reference for owners & inspectors.
  Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page 'Promo/Redemption' space.
  TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop Weldon & Associates
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page 'Promo/Redemption' space.
  
• 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.
  Or choose the The HOME REFERENCE eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page 'Promo/Redemption' space.
  
• Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd
  COMMERCIAL BUILDING INSPECTION COURSES - protocol ASTM Standard E 2018-08 for Property Condition Assessments
  HOME INSPECTION EDUCATION COURESES (Canada)
  HOME INSPECTION EDUCATION COURSES (USA) including home study & live classes at eleven colleges & universities.
  HOME INSPECTION EDUCATION: HOME STUDY COURSES - ASHI@Home Training 10-course program.
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page 'Promo/Redemption' space. InspectAPedia.com editor Daniel Friedman is a contributing author.
  
• The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones

If you see cracks in your external walls then you may well be worried that the structural integrity of your home is at risk. There is no need to panic, however, as only a small amount of cracks are symptomatic of a more serious underlying structural problem. The majority of the time these cracks can be easily repaired. This guide provides information around determining the type of crack you have, what course of action to take in particular how to repair your walls using crack stitching.

Repairing Cracks in Walls: What Do I Do?

Cracks appear in a wall for a number of reasons. They can occur as a new house ‘settles’ or when the construction materials expand and contract overtime with environmental changes. They can also be caused when the foundations of the house move. It is important to establish the root cause and then to take professional advice before making a judgement as to what action to take. Some minor cracking occurs naturally and there is no need for concern or action although it is always worth monitoring them closely for any change. There are other cracks that will need some form of repair work and others that will need more immediate and drastic attention.

Repairing Cracks In Thermalite Blocks Prices

Categorising Cracks

The BRE (Building Research Establishment), who offer expert advice for the built environment sector, produced the BRE Digest 251 Assessment of Cracks in Houses. In this document, they identified six categories for cracks, which they describe along with the recommended crack repair method. You can see the categorisations below:

Usefully, the BRE link the width and number of cracks to the appropriate type of repair. The first three types of crack - 0, 1, 2 – only require redecoration and no major work. Those cracks described in 3 and 4 require more major work but it is only the fifth type of crack that indicates severe structural damage and needs urgent attention from a professional surveyor.

It is important to point out that even with smaller cracks, you should monitor them over time in case they increase in width. Any increase could be indicative of a more serious underlying issue. Those cracks that emerge over a short space of time, even small ones, are also potential causes of concern when compared to those that have been there for years.

Consult a professional structural engineer to confirm any diagnosis as well as an appropriate course of action.

Important Questions

If you consult a structural engineer or building professional they will want to know the following:

• How long have the cracks been there?
• Are they getting wider?
• Are they increasing in number?

It is worth making notes as to when any new cracks appear and take measurements. A pencil line can be drawn across the crack to monitor its movement.

Identifying Cracks in External Walls

There are two main types of crack that can appear in your masonry walls – vertical and stepped.

Vertical Cracks

Vertical cracks usually occur in foundation walls when there is insufficient support below. The main reason for this lack of support is when the soil beneath the foundation has not been properly compacted and compresses or even washes away.

The following is an example of a vertical crack:

Stepped Cracks

Stepped cracks usually follow mortar joints and are most common near the corners of buildings. They usually occur through wall movement related to foundation movement including subsidence.

The following is an example of a stepped crack:

Why Are My Walls Cracked?

Cracks in walls can occur for a number of reasons. With new build houses, cracks can appear as the house ‘settles’ (settlement of soil due to the weight of the building). In older properties small cracks can be fairly common as building materials shrink overtime. We have divided the main causes of cracked walls into structural and environmental factors:

Structural

• Subsidence – Subsidence is the downward movement/sinking of the ground that supports a building. These changes in ground conditions under and around a building can cause walls to move and cracks to appear. Subsidence is more common in areas with clay soil (mainly in the South of England), which can shrink in dry weather. Sandy and silty soils in the foundations can experience leaching when minerals get washed away. For more on Subsidence, read this guide from the ABI.
• The shrinking, drying out and degradation of construction materials like timber, plaster, and concrete.
• Structural failure – if an element of your house has been built incorrectly and subsequently fails then this can cause cracks to appear in your home.
• Corrosion of wall ties.
• Failure or damage of timber lintels over windows and doors.
• Mining – in former coal mining areas subsidence can occur.
• Heave - refers to upward ground movement as soil expands due to an increase in moisture content. When older trees and shrubs are removed, the ground can swell up as the moisture the tree had previously removed builds up.

Environmental

• Thermal expansion – this usually affects long or tall brick walls and the overall superstructure of the building. Cracks occur when the brick work is exposed to summer heat and there is a lack of sufficient control joints or expansion joints.
• Leaks – over time leaks can cause water to get into the render and for walls to crack.
• Freezing – ice can affect the render.
• Decay of materials.
• Moisture and temperature changes – significant changes in temperature and moisture like driving rain.
• Vibration from heavy traffic.

Internal Cracks

You may also experience the following types of internal crack in your home:

Internal Cracks in Plaster Walls

Cracks in plaster walls can occur if the plaster dried too quickly, if it was mixed incorrectly or as part of environmental change (like temperature/moisture) in your home over time. These types of cracks can be resolved with simple repairs. If the cracks return, are more than 5mm wide and/or there are corresponding cracks on the external wall then it could suggest wall movement and structural issues. These will need to be investigated.

Cracks around Windows and Doors

If you have cracks around a window or door, then these can be down to the failure of an old timber lintel or a shift in the foundations.

How to Repair Cracks in Walls

There is an inexpensive and highly effective way of repairing cracked walls called crack stitching. With a crack stitching kit you can repair vertical and stepped cracks to protect the structure of your home. You will need to follow instructions closely when repairing cracks in walls.

What is Crack Stitching?

Crack stitching is a permanent solution to cracks in masonry walls. It involves embedding stainless steel helical bars into horizontal slots into the mortar bed joints of your wall to restore structural integrity.

When do I need Crack Stitching?

If you have identified and resolved the underlying issue that is causing the cracks in the wall to appear, you are then a position to repair the cracks in your walls. Even if you have smaller cracks, it is worth repairing them sooner rather than later as water ingress from leaks or driving rain can make the problem worse. Only once the root cause of the cracks has been resolved you can progress with crack stitching.

How do I Use Crack Stitching

1. Cut a slot in the mortar bed just over 500mm either side of the vertical crack and to the correct depth, dependent on the wall thickness (see the chart below).

2. Ensure the mortar is completely removed to reveal the top and bottom faces of the masonry. Remove all loose material (you can use a blow out pump) and then flush the joint with water. Normally vertical spacing is every 4 - 6 brick courses but check with a structural engineer if in doubt.

3. Mix the PermaCEM Anchor Grout thoroughly using the paddle mixer provided and load into the gun. Pump the grout to the back of the slot in a continuous even bead to approximately two thirds of the slot depth.

4. Push the helical bar firmly into the grout, making sure that the bar extends 500mm either side of the crack.

5. Apply a second bead of grout into the slot making sure that the bar is completely covered and with the trowel provided force the grout into the slot until it is approximately 10mm from the surface and ensuring that the bar and grout are firmly packed.

Thermalite Products Inc

6. Finish by making good the bed joint and filling the vertical crack with an appropriate filler to match.

Read our full How to Guide on Crack Stitching.

Tips

If two or more cracks are close together then bars can be lapped (overlapped) ensuring that the bar extends 500mm either side of the outer cracks and that the laps are at least 500mm.

Thermalite Lightweight Building Blocks

Helical bars should be bent and bonded at least 100mm around corners when cracks are within 500mm of the corner or a reveal etc. This system can be used for rendered or plastered walls.

Crack Stitching Products: What I Need to Repair Cracks in Walls

Permagard sell specialist crack stitching kits, which provide all you need to repair cracks in your wall. Our kits contain helical spiral bars, special grout, a mixing paddle, a mortar gun with nozzles as well as a trowel. Permagard offer both a standard crack-stitching kit and a heavy-duty kit for larger cracks.

Repairing Cracks In Thermalite Blocks Price Per Block

Permacem Grout – grout the steel bars into place using Permacem Grout. This shrink compensated grout with added polymer additives which sets around the helical bar and develops compressive strength rapidly to prevent axial deflection of the helical bar under load conditions.

Products

1. Crack stitching kits

2. Heavy duty Crack Stitching

Permagard – Over 30 years’ property maintenance experience

Permagard are proud of our technical team who are available to advise you on all aspects of crack stitching. Whether you are a specialist installer or want help with installation our technical advisors are here to help. Give us a call today on 0117 982 3282.

Further Reading