Home > Waterproofing > Correctly Repairing Stucco Cracks Key to Long Term Waterproofing Success

Correctly Repairing Stucco Cracks Key to Long Term Waterproofing Success


Photo 1: All cracks in stucco need to be repaired

The exterior walls of an occupied building should, among other things, prevent excessive air and water from entering to the interior. In Florida, stucco is a common choice for exterior wall cladding, but after time, cracking can become a problem. Although control joints are typically used during construction to minimize stucco cracking and to accommodate building or thermal movement, and although construction standards apply to the use of these joints, cracks can still occur.

In most cases, stucco cracking is simply a normal part of the aging of a building during the first few years after construction since the building will experience settling and movement that commonly appears as cracks in the stucco. However, stucco cracks can compromise the weather resistance of the exterior wall, and under the right conditions are potential moisture intrusion points. Factors such as crack/void size, location, wind direction and wind speed will determine where and how rapidly the water enters into or through the stucco.

Stucco cracks should be repaired, but too often we see that an elastomeric coating is recommended because it provides the “advantage” of a crack bridging ability. While these coatings can accommodate the thermal movement, withstand wind driven rain, and provide a long term warranty, they do not bridge or repair existing cracks. The crack bridging ability applies to new cracks that may occur after the stucco has been coated.

When exterior building maintenance is undertaken after the first few years of building life, or anytime thereafter, cracks need to be repaired as part of preparation for a the new paint coating. This is a standard coating manufacturer’s requirement, and these repairs are normally included as part of the manufacturer’s warranty. By correctly identifying the cracks and implementing the proper repair before re-coating walls, it is possible to provide successful long term performance.

Stucco cracks generally include two types. These are static or dynamic (moving) cracks. Static cracks are often hairline in size and less than 1/16th inch in width, and these tend to have a crazed or spider web pattern. The reasons for this type of cracking vary, but the cracks are considered non-moving.

static cracks

Static Cracks Example 1

static cracks example

Static Cracks Example 2

Dynamic cracks are normally larger and occur because of ongoing movement occurring at the crack location. The most common locations for dynamic cracks are cold joints between different substrates such as the joints between poured concrete and wall framing or CMU blocks. Other common locations include intersections of vertical walls and the corners of wall openings such as for windows and doors.

Dynamic Cracking Example 1

Dynamic Cracking Example 2

Repairing stucco cracks prior to re-coating a building requires a thorough inspection, and since different types of repairs are required for different types of cracks, the inspector needs to identify the cracks accordingly. To assure finding all the cracking, the inspections should be done in the cool of the day when the crack is at its largest. If the finish of the stucco creates a contrast, evenly fog the surface with moisture and as the surface dries, the cracks are more easily identified. The cracks should be traced with Magic Marker pens for identification and different colored pens can be used to identify the type of repair that will be necessary.

Inspect and mark location of all cracks with Magic Marker pens.

Different colors for different cracks.

The repair of smaller and static cracks generally uses a brush-grade acrylic elastomeric patching compound over the crack which is feathered out at the edges. At larger static cracks, the crack is raked out to form a “V” shaped groove and a knife-grade acrylic elastomeric patching compound is then installed in the groove and feathered at the edges. For dynamic cracks and other cracks larger than 1/16” wide, the crack location is to be ground or saw cut to create a joint that is filled with polyurethane sealant.

Smaller Static Crack Repair

Larger Static Crack Repair

Crack repair work should be completed by a qualified and experienced remedial Waterproofing Contractor. Their personnel are familiar with the crack repairs, stucco preparation and the coating systems.

Dynamic Crack Repair Example 1

Dynamic Crack Repair Example 2

Before starting the work, a sample area representing the full scope of crack repairs should be selected as a mock-up. The mock-up can be completed for acceptance and approval of by all parties before proceeding with the work. In this way, adjustments to the repair process and scope can be made before the work begins, and the mock-up serves as a basis of acceptable work for the balance of the building.

Repairs

Repairs

Completing crack repairs in the exterior stucco is part of the preparation for a warranted, exterior coating application. However, it should be noted that additional cracking may occur during the course of the warranty, and as a result, future leaking could occur. Therefore, maintenance inspections and crack repairs should be done regularly.

Peter R. Craig specializes in the exterior waterproofing of exterior walls, decks, and below grade areas. Born and educated in Cape Town, South Africa, he has been with Glazing Consultants since 1997. He has over 25 years experience in the waterproofing industry in both new construction and restoration waterproofing. He combines his extensive knowledge of products, techniques and his practical experience to provide answers, solutions, guidance and long term maintenance programs. His expertise includes stucco, EIFS, vertical wall coatings, expansion joints, concrete repair materials, deck membranes and sealers, and sealants.

Mr. Craig is a member of ASTM and CSI and a certified third party inspector for CETCO Waterproofing products. He has also been the featured speaker at numerous Building Managers and Condominium Association meetings and has published articles in the past for Condominium Management Magazine.

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  1. David Champoux
    May 17, 2012 at 1:35 pm | #1

    Informative Article. Thanks!

    David Champoux, M.Eng. P. Eng
    Apec Consulting Engineers Ltd
    Cayman Islands

    • May 18, 2012 at 3:35 pm | #2

      Thanks, David!

    • Laurie
      October 12, 2013 at 11:49 pm | #3

      I agree with your comment 100 percent. I am preparing to paint my house myself and upon closer inspection, noticed several hairline cracks all over our house. I believe it must have been from the insulation that we had installed via the (punch in and blow) method. They patched the holes, but left a pathetic attempt at matching the surrounding concrete. What was left were obvious spots that look like they just threw a little sand on the patch and called it a day. It was not until now that I got up close and saw all the spider cracks. My husband is eager to get the job done and doesn’t want to fuss over small details like this, but I am just the opposite and feel that it should be done carefully and correctly even if it does slow down the process. I am a pretty artistic person but know nothing about stucco and spackle except what I’ve read or seen on my internet searches. I got materials ( Filler for the gun and the premixed stucco patch in a tub). I just haven’t found a video that shows the techniques to finish it off so it does not look obvious. I really want to blend in those patches and cracks. Any suggestions?

  2. May 18, 2012 at 9:14 am | #4

    Good morning, I agree with the entire article as written but one important point was missed and is often missed in the field. I also have worked in this field for over 20 years and have fought this battle forever it seems. The applicator rarely takes the time to make the finished appearance of the repaired area match the adjacent wall areas. This is evident in the repair photos that you have posted. Brush marks and worm trails from routing out the cracks should be detailed more thoroughly before the finish coating is applied. All of the patching materials listed tend to shrink when curing. Some materials shrink up to 50% of their wet mil thickness. I have learned over the years that you will have a better looking finished product if you make the applicator apply these elastomeric patching compounds in a manor that matches the stucco finishes. After the urethane sealants have cured (and shrank) I make the contractor apply another “lift” of sealant to make the cured sealant flush with the adjacent wall sections. Then after that layer has cured properly, have the contractor go back and apply knife grade over the crack repairs in such a manor to make the repaired area blend with the surrounding areas. If the stucco finish is skip troweled, the patching compound also gets skip troweld, and not just over the crack, 2-3 feet wider than the crack repair. The same principal applies to minor, static repairs, simply applying the brush grade with a chip brush 3 inches wider than the crack does not result in an acceptible finished appearance. It is very important to make the applicator feather out, or blend the repair material to try to match the stucco texture prior to painting. Crack repairs are very important and will never go away completely, but to me, if additional time is spent trying to make the patched areas match adjacent walls prior to finish coating, it is well worth the additional time and material. Unfortunatly, todays applicators tend to worry more about speed rather than finished appearance of the repaired areas. This is evident throughout the field as well as in the finished photos posted.

    • May 18, 2012 at 5:45 pm | #5

      I agree that the ultimate success is based upon the experience and skill of the applicator, and very often they come up short on aesthetics.

      However, crack repair is like surgery, if you know where and how to look you will always find the “scar”. These are some useful tips and advice. Thanks for reading & sharing. — Peter Craig

    • December 6, 2013 at 9:31 am | #6

      Great article! Thank you for publishing it to the web!
      The following is not meant as criticism, rather simply to possibly assist others who may be searching for help with stucco cracks/issues.
      Behr Elastomeric for Stucco states on the label that it is warranted to briged hairline cracks existing at time of application; whereas the article above asserts that, “While these coatings can accommodate the thermal movement, withstand wind driven rain, and provide a long term warranty, they do not bridge or repair existing cracks. The crack bridging ability applies to new cracks that may occur after the stucco has been coated.”
      Behr’s label states that only cracks greater then 1/16″ must be prepped.
      However, to insure success, we only apply this elastomeric coating by hand with 1 1/4″ nap rollers and always apply 2 coats. This method is very effective and leaves a beautiful waterproof finish.

    • March 17, 2014 at 2:57 am | #7

      I totally agree with you frank on this one. I also noticed that there were previous repairs completed and very tell tale.
      I actually have a similar project coming up this spring. I am coming to florida in April would be nice if it is at all possible to drop in.

  3. May 23, 2012 at 7:34 am | #8

    Well, this is a very helpful post. Thanks for the information you provided.
    consulting engineers Kildare

  4. May 24, 2012 at 6:49 am | #10

    Thanks for sharing such informative as well as clear picture of wall cladding’s.

  5. May 24, 2012 at 5:06 pm | #11

    Agreed Peter, when you hide the “scars” everyone feels better! P.S. Thanks for answering my carpet question on Linkedin! Seems as though we have dabbled in similiar areas. A pleasure sharing with you. Highest Regards, Bob F.

  6. JayD
    May 26, 2012 at 10:39 pm | #13

    Very interesting read. I agree on the repair process and the added asthetic comments. The results of the repair will satisfy the warranty. The asthetic issue is a matter of funding. In This economy it is hard enough to get engineering and owners to pay for the asthetics.

  7. May 27, 2012 at 1:28 pm | #14

    Great topic. You are correct with everything you stated Bob. We have been installing stucco for almost 30 years, We also provide consultation on stucco installations and applications to other professionals in the industry. We find that the correct mix is as much if not more important as the method of application. It is easier to do a stucco patch than to repair cracks seamlessly. The ultimate fix is a resurface with fiberglass mesh embedded into a modified cement basecoat. One can then apply a colored cement or elastomeric stucco finish over entire surface. It is seamless and provides durability to an existing stucco surface. This process has been proven to work on several historic homes and buildings that we have resurfaced. I understand it is a more expensive way to go but it is in my opinion it is the only way to go. It also comes with a warranty. With the exception of an earthquake, you should never again have to worrie about fixing cracks in your stucco facade. We have also incooperated this method (woven fiberglass mesh) into our browncoat before the finish on all our new stucco projects. This practice, with a high quality breathable elastomeric stucco finish has resulted in stucco projects with zero cracks. However, One can never give a 100% guarantee against some cracking on any cement applications due to the nature of cement. Control joints are designed to control cracking, not prevent them, Hence the name “control”. With correct installation, Mix and maintenance you can have a system that will last a lifetime. Thank you Peter for the great topic.

  8. September 10, 2012 at 3:20 pm | #15

    This is great, showing all types of damage and all kinds of repair that can be made. This is an indeed awesome article regarding correct concrete repair!

  9. Brooklyn Stucco Contractor
    January 8, 2013 at 3:03 pm | #16

    Wow, I can’t imagine how much climbing around that man must have done to repair those cracks!

    -Keystone Contracting Corp.

  10. Exterior wall coatings
    May 13, 2013 at 7:56 am | #17

    A brilliant article and the photos here make the whole thing really stand out. We are also involved in this type of work in the UK but usually smaller buildings, with cracked stucco and old exterior textured coatings that require replacing. We normally use SIKA products, specifically a two pack expoxy mortar to fill the cracks before over coating. Great stuff!

  11. January 8, 2014 at 9:01 pm | #18

    Wow! Nice work and blog post. I’m definitely going to use your marker trick from now on.

    Thanks for posting, Paul

  12. jeff
    March 11, 2014 at 6:05 pm | #19

    This was an excellent article

  13. March 17, 2014 at 2:49 am | #20

    I have similar problem here in Calgary Alberta Canada. Question? The photo shows stucco repair is this on acrylic stucco ? I also noticed other stucco repairs from previous failures. Another question is can the repairs be somewhat less telegraphing through.
    Another question what were the repair costs and the painting costs. Would like to know so as I can prepare a budget for the condo association.
    Thanks

  14. Jeff U
    March 26, 2014 at 2:15 pm | #21

    Thanks for this Peter. I am a contractor in California and am currently working through an issue with sealant repairs “broadcasting” though the finish coat of acrylic paint. Can you recommend any solutions to eliminate or greatly reduce this issue? Thanks

    • Dan
      March 26, 2014 at 3:48 pm | #22

      Jeff,

      Do you have any photos of your current project? I’d like to see the texture of the finish.

      What we sometimes do is first fill the cracks with elastomeric sealant and then apply a little bit of “soupy” mix over areas to blend it in.

      If there is a better way, I’d love to hear about it.

      Best wishes!

      Dan

  15. April 9, 2014 at 3:27 am | #23

    The article enlightens us greatly on stucco cracks. Thanks for the same.

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