Updated: Apr 2
Are you looking to parge your concrete or stone walls with mortar? Check out our expert tips and tricks for achieving a flawless finish on your next DIY project.
As an experienced renovation company, we often come across homeowners who want to improve the appearance and durability of their block walls. One of the most effective and budget-friendly methods to achieve this is parging. Parging involves applying a thin layer of mortar to the surface of a block wall, which not only enhances its appearance but also adds a layer of protection against the elements. In this blog post, I'll guide you through the process of parging a block wall using S-type mortar mix, an excellent choice due to its high bond strength and weather resistance.
What You'll Need:
S-type mortar mix
Large mixing tub or wheelbarrow
Parging trowel or plasterer's trowel
Mortar mixer (optional)
Safety gear: gloves, goggles, and mask
Step 1: Prepare the Wall
Before you start parging, ensure that the block wall is clean and free from dirt, dust, or any loose material. You can use a stiff-bristle brush or power washer to remove any debris. Make sure the wall is slightly damp before applying the mortar mix, as this will help the mortar adhere better.
Thinking about how clean a wall should be, just try your best. Mortar mix does have concrete which will form a solid bond with rough surfaces, too much dust will suck out the water from the mix or will cause the bonding to be weak.
Step 2: Prepare the S-Type Mortar Mix
In a large mixing tub or wheelbarrow, combine the S-type mortar mix with clean water, following the manufacturer's instructions on the bag. If available, using a mortar mixer will save you time and ensure a consistent mix. The consistency of the mix should be smooth and spreadable, similar to peanut butter. Allow the mix to rest for a few minutes, then mix again to eliminate any air pockets.
There are many great Youtube channels that show mixing techniques, but one of the best masons I have seen online is Mike Hadock. Just a personal preference of course.
Step 3: Apply the Mortar
Dampen the masonry brush and lightly moisten the block wall. Scoop some mortar mix onto the mason's trowel and apply it to the bottom corner of the wall with the flat side of the trowel, working in a 3-4 ft² area. The first layer should be approximately 1/8 to 1/4-inch thick. Smooth out the mortar using the parging trowel or plasterer's trowel, applying even pressure to create a consistent surface.
The size of the area is really related to weather in your area. If the day is hot day (> 20C), you may need to reduce the size as the mortar will dry quickly. On a cool day (days < 15C), you can work on a larger area.
Also note, that the thicker you make it or the hotter the day is, the more likely it will crack.
Step 4: Build Up Layers
Once the first layer has set for about 30 minutes (or as recommended by the mortar mix manufacturer), apply a second layer of mortar using the same technique as the first layer. This layer should also be 1/8 to 1/4-inch thick. Building up layers helps to create a stronger bond and a smoother finish.
Step 5: Finishing Touches
After applying the final layer and while the mortar is still slightly wet, use the parging trowel or plasterer's trowel to create your desired texture. You can either smooth the surface for a polished look or create a rough texture by using a circular motion with the trowel. Once the mortar is fully cured, you can paint or apply a masonry sealer to further protect the wall and enhance its appearance.
If you see cracks developing, use a slightly damp sponge and sponge smooth that area, and then use the trowel again to have a consistent finish.
Parging a block wall with S-type mortar mix is a straightforward process that can significantly improve the appearance and durability of your wall. By following these steps and using the right materials, you'll achieve a smooth and well-protected surface that will last for years to come.
Other thoughts and experiences...
You need to have at least 1/4" to remove the block lines that you may notice during wetter days. If you notice block lines appearing, you can always apply a second coat.
Sponge finishing can really smooth out a wall and make it look professional and smooth.
If your doing a large wall, tools like a darby can come in handy to help keep the wall flat.
You can parge down to -3C (27F) and still get a good finish, but you need to be pretty familiar with the mortar mixes and the right amount of water.
If the wall that your parging is not flat or is stone, I personally do an initial coat (scratch coat). Make this coat as flat as possible filling in any holes but make the surface rough by lightly running a broom lightly across to leave lines. Let that first coat sit for a day and then follow up with a second smooth coat. In this way, the bottom coat, as it will be thicker then 1/4" may develop cracks, and you can fix that in your second coat.