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How To Prep And Stucco Your Yard's Cinder Block Fence

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Cinder block walls provide a strong and long-lasting barrier around your yard. If you want to change the look of your yard, you can stucco the exterior of your cinder block wall. Here are some instructions to help you with this process.

Clean and Remove Residues

Many types of residue can find their way onto the surface of a cinder block in your yard, such as mold, mildew, efflorescence, and dirt. All these need to be removed from the surface of the cinder blocks before you can apply the stucco coating. Cinder blocks have a porous surface that can pull in moisture, creating the perfect environment for mold and mildew to grow. Any mold and mildew on your wall will need to be treated to kill any spores that can live within the small pores of the cinder block surface. 

To remove and kill any mold and mildew spores, first, use a power washer to clean the entire surface of the cinder block wall. A power washer with a universal yellow-colored 15 degree tip is perfect for cleaning the surface of the wall and removing efflorescence, dirt, mold, and mildew. 

If any mold and mildew stains still remain behind within the wall's pores, create a cleaning solution by combining one-half ounce of trisodium phosphate, or TSP, with one gallon of hot water. Be sure to wear rubber gloves and eye protection while you scrub the deep-set mold and mildew from the cinder blocks with a scrub brush. This treatment will kill any remaining mold spores and prevent their regrowth beneath and damage to your finished stucco layer.

Repair Holes and Cracks

Before the stucco can be applied to the wall, you need to repair and patch any cracks and holes. With a wire brush, remove any crumbled sections of concrete around any cracks and holes. Any crumbling surfaces left behind can cause your repair to be weak and re-break later. 

Mix up concrete patch by combining one part Portland cement with three parts sand, then add water until it makes a thick mixture. Use a concrete trowel to press the concrete patching material into any holes and cracks. Then, use the trowel to smooth over the surface of each repair, making it even with the surrounding cinder block surface. Allow the patching material to dry completely before applying the stucco.

Apply the Stucco

As long as your cinder block fence has not been painted, you can apply the stucco directly onto the concrete wall's surface. If there is a layer of paint on the cinder block wall, you will need to remove it by sandblasting the paint from the surface. 

Select a day to complete the stucco work when the outside temperature will be between 50 and 70 degrees F. Outside temperatures that are too cold or too hot will cause the stucco layers to cure too slowly or too quickly, respectively. Just before you apply the first layer, use your garden hose and a sprayer attachment to mist water onto the surface of the cinder block. A moist surface helps the stucco adhere better to the cinder blocks. Also, make sure you wear work gloves and eye protection, as stucco can be caustic, and contact with it can cause burns to your skin.

Apply the first layer of stucco, the scratch coat, onto the wall with a trowel, pushing the mortar onto the cinder blocks, then smoothing it over. This first layer should be between one-fourth and one-half-inch thick. When the mortar has hardened a bit, use a scoring tool to scratch one-eighth-of-an-inch-deep scores into the mortar in one direction. Then, let the mortar layer cure for 36 to 48 hours. To prevent the scratch coat from drying too quickly and cracking, you may need to moisten it by misting it with your garden hose.

Last, apply the stucco's finish coat with the trowel, creating a layer one-eighth to one-fourth of an inch thick. If you want your stucco wall to be a specific color, you can find and choose a pigmented stucco coating at most home improvement stores. As you apply this coat, be sure to smooth its surface to get an even look. Then allow the stucco to cure for 36 to 48 hours, misting it with your garden hose when it becomes dry.

Use this information to stucco your yard's cinder block wall. Have a peek here for more.


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