Mortar is used to bind cement blocks together and create a strong, durable wall. Laying cement blocks can be a challenging task, but it is made easier with the right tools and techniques.
First, you will need to gather your materials. You will need cement blocks, mortar, a mortar mixer, a trowel, a level, and a rubber mallet. Once you have your materials, you are ready to begin laying the blocks.
Start by spreading a layer of mortar on the foundation. Then, place the first block on the mortar and use a level to make sure it is level. Continue laying blocks, alternating between courses of stretchers and headers. As you lay the blocks, make sure to stagger the joints between the blocks. This will help to create a stronger wall.
Choosing the Right Mortar
Type N Mortar
Type N mortar is the most common type of mortar used for cement blocks. It is a general-purpose mortar that is suitable for most applications. Type N mortar is made with a mixture of Portland cement, lime, and sand. It has a compressive strength of 750 psi and a water absorption rate of 15%.
Type S Mortar
Type S mortar is a high-strength mortar that is used for structural applications. It is made with a mixture of Portland cement, lime, and sand, and it has a higher proportion of cement than Type N mortar. Type S mortar has a compressive strength of 1,000 psi and a water absorption rate of 10%.
Type M Mortar
Type M mortar is a medium-strength mortar that is used for general-purpose applications. It is made with a mixture of Portland cement, lime, and sand, and it has a higher proportion of lime than Type S mortar. Type M mortar has a compressive strength of 800 psi and a water absorption rate of 12%.
| Mortar Type | Compressive Strength (psi) | Water Absorption Rate (%) |
|---|---|---|
| Type N | 750 | 15 |
| Type S | 1,000 | 10 |
| Type M | 800 | 12 |
Preparing the Block Surface
To ensure proper adhesion and a strong bond between the mortar and cement blocks, it is essential to prepare the block surface thoroughly.
### Cleaning the Blocks
Remove any dirt, dust, or debris from the blocks using a brush or compressed air. Use a wire brush for heavy dirt or grime.
### Wetting the Blocks
Thoroughly wet the blocks with clean water. This will help to prevent the blocks from absorbing water from the mortar too quickly, which can weaken the bond.
### Proper Alignment
Check the alignment of the blocks by placing a straight edge or level across them. Make adjustments as needed to ensure that the blocks are stacked evenly and level.
### Spacers and Joint Size
Insert spacers or joint reinforcement between the blocks to maintain the desired joint size. Joint size can vary depending on the block type and structural requirements. A common joint size is 3/8 inch.
| Joint Size (inches) | Spacer Thickness (inches) |
|---|---|
| 3/8 | 1/4 |
| 1/2 | 3/8 |
| 5/8 | 1/2 |
### Check for Bonding Surfaces
Ensure that the bonding surfaces of the blocks are free of any protrusions or debris that could prevent a proper bond between the mortar and the block.
Mixing the Mortar
Ingredients
To mix the mortar, you will need the following materials:
| Material | Quantity |
|---|---|
| Portland cement | 1 part |
| Sand | 3 parts |
| Water | Approximately 1/2 part |
Instructions
- Start by measuring out the dry ingredients into a wheelbarrow or mortar box. Use a shovel or hoe to combine the cement and sand thoroughly.
- Slowly add water to the dry ingredients while mixing with a hoe or trowel. The mortar should be damp but not runny. It should hold its shape when you scoop it up with a trowel.
-
Achieving the Right Consistency
The consistency of the mortar is crucial for proper bonding and durability. Here are the key aspects to ensure the correct consistency:
- Too dry: Mortar that is too dry will not adhere properly to the blocks and will crumble easily.
- Too wet: Mortar that is too wet will be difficult to handle and will not provide sufficient support for the blocks.
- Ideal consistency: The mortar should be damp enough to stick to the trowel without dripping. It should also be firm enough to hold its shape when applied to the blocks.
Applying the Mortar
Once you have prepared the mortars and the cement blocks, you can now proceed to apply the mortar to the cement blocks. You can use a garden trowel or a pointing tool for cement blocks to spread the mortar onto the surface of the blocks.
To ensure a strong bond between the cement blocks, you should apply a generous amount of mortar to the surface of each block. Then use a notched trowel to create small grooves in the mortar. This will help create a mechanical bond between the blocks and reduce the risk of slippage.
4. Using the Mortar Guide
A mortar guide is a handy tool that can help you apply the mortar evenly and consistently. It consists of two parallel bars that are spaced at a specific distance apart. You can use a mortar guide to ensure that the thickness of the mortar is uniform throughout the wall.
To use the mortar guide, simply place it on the surface of the cement blocks and spread the mortar evenly using a trowel. The parallel bars will prevent you from applying too much or too little mortar. This will result in a more stable and durable wall.
Here is a table summarizing the steps to use a mortar guide:
| Step | Description |
|---|---|
| 1 | Place the mortar guide on the surface of the cement blocks. |
| 2 | Spread the mortar evenly using a trowel. |
| 3 | Remove the mortar guide and check the thickness of the mortar. |
| 4 | Adjust the mortar guide if necessary and repeat the process. |
Laying the Blocks
After preparing the foundation and mortar, it’s time to lay the mortar cement blocks. Here’s a detailed guide:
1. Start at a Corner
Begin by placing the first block at one corner of the wall. Ensure it’s level and plumb using a level and plumb bob.
2. Apply a Bed of Mortar
Spread a thin layer of mortar onto the foundation, approximately 1/4 to 1/2 inch thick. Use a trowel to create a level surface.
3. Set the Block
Carefully place the block onto the mortar bed, pressing it down firmly. Use a level to check its levelness and adjust as needed.
4. Place the Second Block
Repeat step 3 to place the second block adjacent to the first. Ensure the sides are flush and the mortar joints are even.
5. Continue Laying Blocks in Rows
| Step | Details |
|---|---|
| a | Apply mortar to the top and side of the previous block. |
| b | Fit the next block into place by tapping it lightly with a rubber mallet. |
| c | Use a level and plumb bob to ensure straight and level rows. |
| d | Fill the mortar joints using a pointing trowel to create clean edges. |
| e | Let the mortar set for several days before applying pressure to the wall. |
Curing the Mortar
Proper curing is essential for the long-term strength and durability of mortar joints. The curing process involves keeping the mortar moist to allow it to harden fully and develop its strength. There are several methods for curing mortar:
1. Wet Curing
Wet curing is the most effective method for curing mortar. It involves keeping the mortar joint saturated with water for at least 7 days. This can be done by spraying the joint with water, covering it with wet burlap, or immersing the joint in a pool of water.
2. Plastic Sheeting
Plastic sheeting can be used to create a humid environment around the mortar joint, which will help to keep it moist. The plastic sheeting should be placed over the joint and sealed around the edges to prevent air from entering.
3. Liquid Membrane-Forming Compounds
Liquid membrane-forming compounds are applied to the surface of the mortar joint and form a thin film that helps to retain moisture. These compounds are typically used in conjunction with wet curing or plastic sheeting.
4. Curing Compounds
Curing compounds are applied to the surface of the mortar joint to form a barrier that prevents moisture from evaporating. These compounds are typically used in situations where it is difficult to keep the joint moist, such as in hot or windy conditions.
5. Integral Curing Compounds
Integral curing compounds are added to the mortar mix at the time of mixing. These compounds help to retain moisture within the mortar and reduce the need for external curing methods.
6. Curing Time
The time required for mortar to cure properly depends on several factors, including the type of mortar, the temperature, and the humidity. The following table provides approximate curing times for different types of mortar:
| Mortar Type | Curing Time |
|---|---|
| Type N | 7 days |
| Type S | 10 days |
| Type M | 14 days |
Leveling and Aligning the Blocks
Precision in leveling and aligning cement blocks is crucial for the stability and aesthetics of your project. Here’s a detailed step-by-step guide to ensure accuracy:
1. Establish Corner Blocks:
Lay the first corner blocks on top of concrete footings or other supporting structures. Check their level using a spirit level and adjust as needed.
2. Set the String Lines:
Stretch two taut string lines perpendicular to each other at the height you want the top of the blocks to be. Position the lines along the outside edges of the corner blocks.
3. Check for Perpendicularity:
Use a crossline laser level or a square to ensure the strings are forming a perfect 90-degree angle. Reposition the corner blocks if necessary to establish a true rectangle.
4. Mark the Lines:
On the corner blocks, mark the desired height of the top of the blocks based on the string lines. These marks will serve as a reference for leveling the subsequent blocks.
5. Lay the First Course:
Starting from a corner, spread mortar on the bed joint (horizontal surface) of the first block. Place the block in position, aligning it with the marked lines and string lines. Use a level to ensure it’s level both horizontally and vertically.
6. Continue Laying Blocks:
Spread mortar on the bed joint and the end joint (vertical surface) of the next block. Place it against the previous block, aligning it with the string lines and leveling it as described in step 5. Repeat this process for the entire first course.
7. Check and Adjust:
After completing each course, check the level of the blocks using a spirit level. If any blocks are uneven, use a rubber mallet to gently tap them into place. Adjust the strings as needed to maintain the desired height and alignment. The table below summarizes the steps involved in this process:
| Step | Action |
|---|---|
| 1 | Mark the desired height on the corner blocks. |
| 2 | Spread mortar on the bed joint and end joint. |
| 3 | Place the block in position, aligning it with the marks and strings. |
| 4 | Use a level to check both horizontal and vertical levels. |
| 5 | Adjust the block with a mallet if necessary. |
Finishing the Joints
After the mortar has set for a few hours, it is time to finish the joints. This can be done with a variety of tools, including a jointing tool, a tuck pointer, or a trowel. The goal is to create a smooth, finished appearance that will help to protect the mortar from the elements.
To finish the joints with a jointing tool, hold the tool at a 45-degree angle to the joint and press down firmly. Drag the tool along the joint, applying pressure to create a smooth, even surface. You can also use a tuck pointer to finish the joints. A tuck pointer is a small, triangular tool that is used to create a recessed joint. To use a tuck pointer, hold the tool at a 90-degree angle to the joint and press down firmly. Drag the tool along the joint, applying pressure to create a recessed surface.
If you are using a trowel to finish the joints, hold the trowel at a 45-degree angle to the joint and press down firmly. Drag the trowel along the joint, applying pressure to create a smooth, even surface. You can also use a trowel to create a variety of decorative finishes. For example, you can use a trowel to create a raked joint, a beaded joint, or a weathered joint.
The following table provides a summary of the different jointing tools and their uses:
Jointing Tool |
Use |
|---|---|
|
Jointing tool |
Creates a smooth, even surface |
|
Tuck pointer |
Creates a recessed joint |
|
Trowel |
Creates a smooth, even surface or a variety of decorative finishes |
Troubleshooting Common Problems
Despite careful planning and execution, problems can arise when mortaring cement blocks. Here are some common issues and their solutions:
Problem 1: Mortar is too wet
Solution: Add more dry mortar mix to thicken it.
Problem 2: Mortar is too dry
Solution: Add more water to thin it.
Problem 3: Mortar is sticking to the trowel
Solution: Wet the trowel slightly or use a mortar retarder to slow down the setting time.
Problem 4: Mortar is not bonding to the blocks
Solution: Ensure blocks are clean, wet the blocks before applying mortar, and use a bonding agent.
Problem 5: Mortar is cracking
Solution: Use a flexible mortar or incorporate expansion joints to accommodate movement.
Problem 6: Mortar is freezing
Solution: Use cold-weather mortar or cover the blocks with tarps during freezing temperatures.
Problem 7: Mortar is too crumbly
Solution: Use a higher quality mortar mix or add a plasticizer to improve workability.
Problem 8: Mortar is bleeding (water separation)
Solution: Reduce water content or use a mortar with lower water retention.
Problem 9: Mortar is efflorescing (white crust forming on the surface)
Solution: Use a mortar with low soluble salts, apply a water-repellent sealant, or cover the blocks to prevent water penetration. Efflorescence is often a cosmetic issue and does not typically affect the structural integrity of the wall.
Table: Troubleshooting Mortar Bleeding
| Cause | Solution |
|---|---|
| Excess water | Reduce water content |
| Poorly mixed mortar | Mix mortar thoroughly |
| High wind or sunlight | Cover blocks to shade from sun and wind |
| Rapid drying | Moisturize the mortar during the curing process |
Tips for a Strong and Durable Mortar Joint
A well-constructed mortar joint is crucial for the strength and durability of a block wall. Here are some tips to help ensure a strong and long-lasting joint.
Use high-quality materials: Choose a mortar mix that is specifically designed for blockwork and that meets industry standards.
Mix the mortar properly: Follow the manufacturer’s instructions for mixing the mortar. Use clean water and mix until the mortar is smooth and has a slightly wet appearance.
Apply the mortar evenly: Use a trowel to apply a thin and even layer of mortar to the surface of the block. Avoid applying too much mortar, as this can weaken the joint.
Set the blocks firmly: Position the blocks firmly against the mortar and tap them down with a rubber mallet. Ensure that the blocks are level and plumb.
Cure the mortar: Allow the mortar to cure properly before applying any load to the wall. Keep the wall protected from the elements and allow it to dry slowly.
Use a flexibilizing additive: Consider adding a flexibilizing additive to the mortar mix. This can help prevent cracking and improve the joint’s resistance to movement.
Add reinforcement to the joints: For walls that will experience heavy loads or movement, consider adding reinforcement to the joints. This can be done with metal mesh or reinforcing wire.
Inspect the joints regularly: Inspect the joints periodically for any signs of cracking or deterioration. Repair any damaged joints promptly to prevent further damage.
Use expansion joints: Provide expansion joints at regular intervals to allow for building movement. This can prevent excessive stress on the mortar joints.
Consider using a backer rod: A backer rod can be inserted into the joint before applying the mortar. This provides a compressible material that allows for movement and prevents the mortar from bonding to the sides of the joint.
By following these tips, you can ensure that your block wall has strong and durable mortar joints that will last for years to come.
Laying Mortar Cement Blocks
Laying mortar cement blocks is a quick and straightforward process that can be completed in a few simple steps. However, it is important to take your time and ensure that each step is completed correctly to achieve a strong and durable wall.
To begin, you will need to gather your materials: cement blocks, mortar, a trowel, a level, and a rubber mallet. Once you have your materials, you can start by laying out the first course of blocks on a level surface.
To lay a block, start by applying a 1/2-inch layer of mortar to the bottom of the block. Then, lift the block into place and gently tap it with a rubber mallet to settle it into the mortar. Use a level to ensure that the block is level, and adjust it as necessary.
Once the first course of blocks is complete, you can continue laying subsequent courses in the same manner. Be sure to stagger the joints between the blocks to create a stronger wall. As you lay each course, check the level and make adjustments as needed.
If you are laying a wall that is longer than 8 feet, it is important to install control joints. Control joints are vertical gaps in the wall that allow it to expand and contract with temperature changes. To install a control joint, simply leave a 1/2-inch gap between two blocks and fill it with a sealant.
Once you have finished laying the wall, you can smooth the mortar joints using a tuckpointing tool. This will give the wall a finished appearance and help to prevent water from penetrating the joints.
People Also Ask about How To Mortar Cement Blocks
How thick should the mortar joints be?
The mortar joints should be 1/2-inch thick.
Do I need to use control joints?
Yes, if the wall is longer than 8 feet, you should install control joints.
How do I smooth the mortar joints?
You can smooth the mortar joints using a tuckpointing tool.
