Stucco Repair Basics Step by Step


Stucco repair can be one of the easiest do-it-yourself projects around, or it can turn into a nightmare if you’re not exactly sure of what you’re doing.

Learn the basics of stucco first, before you get in over your head.

Stucco exteriors are insulating, which makes heating and cooling a property easier and more energy-efficient. They are fire retardant, reduce outside noise, and, when properly maintained, can last for a very long time.

Proper stucco installation is carefree, looks great, and can last for over a hundred years. However, if cracks or holes are noticed, repair stucco the right away, before the damage has a chance to spread.

Repairing Hairline Cracks in Stucco

If you’re worried about costs for repairs, the good news is that small, hairline cracks (¼” wide and below) in the stucco surface can be easily fixed with exterior latex paintable caulk.

Be sure to choose a caulk color that matches the stucco of your building, or at least comes pretty close. If need be, once the caulk has been applied and set, a touch-up with exterior paint can be done to even the colors out. 

For cracks or small holes in your exterior wall larger than ¼”, opt for using a store-bought pre-mixed stucco patch. With a trowel or small putty knife, fill the crack with the stucco patch and allow it to set for the manufacturer’s recommended time.

You may need to do a few layers in order to fill the stucco crack repair so it’s flush with the rest of the wall.

Much like drywall repair work, the important part of this home improvement DIY project or stucco finish repair work is to follow manufacturer instructions.

Pro Tip – Use Quikrete Stucco Repair to fill and seal cracks in stucco up to 1/2” wide. It’s a completely weather-resistant formula that has great flexibility and adhesion. There’s also a Quikrete Stucco Repair sealant applied with a caulk gun for crack filler and stucco siding repair.

stucco repair
A crack in stucco at a jobsite in Port Saint Lucie, FL. Stucco is more common in the southern half of the country, and more stucco repair contractors are available in these areas.

What to Do for Larger Scale Stucco Repair

If hairline cracks or minor cracks turn out to be connected to a series of larger cracks, you want to take swift action.

Cracks in stucco siding can happen for a variety of reasons. From improper mixing of the plaster to normal house-settling. The important thing for homeowners to remember is that larger cracks in your exterior wall need to be addressed as soon as possible.

Larger cracks cause problems behind the stucco wall where water will collect. It will eventually soften the stucco and cause it to crumble or fall off in sheets. Water damage is no joke when it comes to stucco.

If you’ve spotted larger cracks in an exterior wall, holes, or pieces of stucco that are crumbling, you’ve got a stucco repair project on your hands. You can contact a stucco repair contractor or a handyman in your area who is experienced with stucco wall repair. There are usually a few quality stucco services ready to respond.

However, as DIY projects go, you can save a decent amount of money by going it alone. Grab your utility knife, here are the basics for a DIY stucco repair job.

What is Stucco and How to Make It

Stucco is a lime-or-cement-based plaster that can easily be made at home via a simple mix. It is applied to exterior wall finishes in a three-coat system to ensure proper setting, sealing, and insulation.

The three-coat system consists of two base coats and a finish coat.

The first coat is called the scratch coat, and the second coat is called the brown coat.

After each coat, it’s important to allow enough curing or setting time to ensure the plaster has sealed to the building and to allow the next coat to seal to the prior one.

There are dozens of different stucco coat recipes out there depending on the type of material that you’re working with and the building you’re plastering.

In general, stucco is made by mixing cement and sand together in different proportions depending on the coat. First coats, or scratch coats, are made with 1 part cement to 2 ¼ – 4 parts cement.

Second coats, or brown coats, are made with 1 part cement to 3 – 5 parts sand. Finish coats are made with 1 part cement to 1 ½ – 3 parts sand.

Here are the basic recipes for stucco mix:

First Coat:

  • ½ bag (47 lbs) Portland cement
  • 6 shovels brick or mason’s sand, slightly damp
  • 1 shovel hydrated lime
  • ½ cup acrylic bonding agent

Second and Finish Coats:

  • ½ bag (47 lbs) Portland cement
  • 8 shovels aggregate sand for concrete
  • 1 shovel hydrated lime
  • ½ cup acrylic bonding agent

Directions:

  1. Put all dry ingredients into a wheelbarrow and mix them together with a hoe
  2. Add the acrylic bonding agent, then mix in water, a little at a time, until the mixture reaches the consistency of thick cake frosting (too much water will make the stucco mix loose and unusable).
  3. Once properly hydrated, the mix can be used for 30 to 90 minutes before it begins hardening.

*These instructions and proportions are a base recipe that can be modified for your project. If you need to cover fewer square foot area for your stucco mix, cut the stucco mix recipes down accordingly.

How to Repair Stucco

With the basics of stucco mixing and coating down, here are the basic steps for repairing stucco.

Step 1: Remove Broken or Loose Stucco

In order to repair stucco, the first step is to remove all broken or damaged stucco. Identify where crumbling, loose pieces or cracked stucco is, and get started removing it.

It can be removed with a hammer or a hammer-and-cold chisel, but take care not to damage any of the wooden structure behind the stucco. Protective eyewear is a must in this step.

Depending on the accessibility and location of the repair, scaffolding may be needed to ensure access to the entire damaged area.

Step 2: Keep Chipping at the Edges

Continue breaking away pieces of damaged stucco until you get to nothing but solid, firmly attached stucco. This step ensures that there isn’t any loose or damaged stucco around the edges of the repair.

stucco repair

Step 3: Inspect/Replace Metal Mesh

Once the damaged stucco has been removed, inspect the metal lath beneath for damage or signs of rust. If it appears to be in good condition, you can apply new stucco directly to the mesh.

If the old mesh is damaged, remove it with metal snips. Trim a piece of grade-D builder’s paper to fit snugly in the stucco opening and affix it to the wooden lath with roofing nails.

Apply a second layer of paper. Place galvanized metal mesh over the paper and trim it to fit tight against the edge of the stucco. Drive more nails through the mesh to secure it against the wood lath.

Step 4: Mix a Batch of Stucco

Use the first coat recipe to make a batch of stucco mix. Modify the quantity to make as much as you need to use within a short window since the mix will dry and harden beyond use within a couple of hours. 

***Wear gloves when mixing stucco and avoid touching fresh stucco with bare skin. The alkalis in stucco mix can cause burns. Keep a hose or water bucket nearby to wash off any exposed skin touched by fresh stucco.

Step 5: Apply New Stucco

Wet the edges of the existing stucco to ensure better adhesion and to prevent the old stucco from sapping the water from the new layer. Scoop wads of wet stucco into a masonry trowel and sling them at the mesh until the mesh is covered.

Smooth the mix with a trowel and pack it against the edge of the existing stucco. Keep adding more wet stucco until this layer is about ½ inch below the stucco exterior.

Step 6: Scratch the Scratch Coat

The coat just applied is the base coat or scratch coat. After a few minutes, once the wet stucco loses its wet sheen, scratch a series of X patterns into the scratch coat using the edge of a trowel.

This scoring helps improve the adherence of the second, brown coat.

Once scored, tape a plastic sheet over the area to prevent it from drying out too much.

The scratch coat will need sufficient time to cure in order to become rigid enough to stop cracking and be ready for the second coat. This cure should last around a week or seven days.

Step 7: Apply the Brown Coat

After the first curing period, mix together a batch of stucco for the brown coat. Remove the plastic sheet, mist the patch with water, and apply a ¼ to ⅜ inch layer of brown coat.

Once the wet sheen dissipates, smooth the layer just below the existing stucco, being sure to pack down the edges. Cover again with a plastic sheet for another curing period. This cure should only take about three days.

Step 8: Apply the Finish Coat

After the cure, remove the sheet and mist the patch with water from a spray bottle. Mix up a batch of finish coat using the finish coat recipe as a base, and apply.

Do your best to apply this top coat flush with the existing wall, making the entire surface smooth.

This step is also where the stucco gets its distinctive textured finish. Different methods of application result in different types of finish.

The traditional, stippled, and rough texture of stucco can be replicated using a damp cloth or sponge.

Step 9: Let the Finish Coat Cure Before Painting

Now that the stucco has been applied and repaired, you’ll likely want to jump the gun and get to painting to create a seamless finish.

However, this layer, like the others, needs time to cure before paint of any kind can be applied. Wait a week before painting.

The basics of stucco repair.

Important Tips for Stucco Repair

With the methodology of stucco repair covered, here are a number of miscellaneous bits of information to help the process.

Weather and Stucco

Wet stucco should be kept at a minimum of 40℉. Wait for a time when the nighttime temperatures are above 40℉.

The stucco can be kept above that temperature by covering it and heating the building, but it’s most important to not let the stucco freeze within 48 hours of application. This damages the structural integrity of the stucco.

Finishing Stucco

You may have noticed that in the steps above I didn’t mention matching the stucco mix color to the existing color.

While you can add mortar colorants to wet stucco mix to tint them, it’s incredibly difficult to exactly match the color of a freshly applied stucco to existing stucco.

The only way to perfectly match a color is to cover the stucco with a pigmented coating of some sort. That can be anything from concrete paint to a fog coat to the sprayed-on acrylic elastomer. All are ways to color and tint the exterior finish of stucco.

Cleaning Stucco Repair Spills

Stucco Spills are bound to happen in a project like this, and they can be a pain. The plaster will harden on the ground and stain concrete and wooden floorings.

However, with a simple wire brush, stucco spills can be cleaned.

  1. Wet spilled stucco with water by soaking it with a wet cloth for 10 to 15 minutes until saturated.
  2. While wearing eye protection and gloves, break the stucco up with a chisel and mallet, especially if it’s a large spill.
  3. Scrape up the spill with a wire brush. Dispose of stucco.
  4. If the stucco left behind a stain, mix 1 part vinegar to 5 parts water and spray the affected area with the mixture. Scrub the area with the wire brush until the stain is gone.
  5. Rinse the area thoroughly.

Synthetic Stucco

If you’re not ready to replace the entire building with vinyl siding, another plaster option is to replace old traditional stucco with synthetic stucco, also known as EIFS.

While traditional stucco is much more susceptible to cracking, EIFS is much more crack-resistant because it bonds together with a protective finish that doesn’t breathe.

Even though Exterior Insulation Finish Systems (EIFS) is more durable and vapor permeable, moisture can get trapped behind the entire wall causing damage to the structure and possible bigger problems down the road.

As with every type of stucco and EIFS, it’s critical to follow proper installation methods.

Be Careful with Old Traditional Stucco

If you’re dealing with an old building with its original stucco intact, it’s possible your building has traditional stucco. Stucco contractors are pretty quick to identify old traditional stucco. But if you want to do it yourself, here are a few tips.

New stucco is made with a similar mixing method but uses Portland cement as the main material rather than the traditional, softer lime.

Lime is added to new stucco to make it more workable, whereas traditional stucco is made with exclusively lime, sand, and water.

It’s important to check old stucco to see if it’s made the traditional way before beginning to repair stucco that’s Portland cement-based.

You can do this by taking a piece of chipped-off stucco and submerging it in water. If the piece softens after being submerged, it’s likely lime-based stucco which cannot be replicated with today’s building materials.

If your building is plastered with old, lime stucco, it’s not a bad idea to contact a stucco repair contractor to get a second opinion on structural integrity when repairing with Portland cement.

Flexible sealants are best for stucco cracks. But you need to know the basics of stucco repair first before you get in over your head.

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1 thought on “Stucco Repair Basics Step by Step”

  1. I think this is the most comprehensive article on how to stucco a patch on the web. I mean ya really went into detail with different types and even how to clean spilled stucco! I never would have thought to use a vinegar water mix to clean up the stained stucco after a clean up.

    Above and beyond, awesome article.

    Jon

    Reply

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