How to Point Slabs with Cement

Here is how to point slabs with cement, describing the traditional method.

Pointing (or jointing) slabs with cement involves filling the gaps between patio slabs or paving stones with a cement-based mortar mix to create a durable and stable surface.

The Traditional Cement Pointing Method

The original and traditional method of cement-based patio jointing is a hands-on process that requires creating a mortar or grout mix from scratch. As noted in the reference, this involves taking sand, cement, and water and combining them together in the correct ratio. Getting this ratio right is highlighted as a tough task in itself.

Once the mix is prepared, the process involves using the resulting mixture to fill the gaps between your slabs. This traditionally means inserting the mix into each gap, one painful joint at a time. This method is labour-intensive but can provide a strong, rigid joint when done correctly.

Materials Needed

To point slabs using the traditional cement method, you will need:

• Sand: Typically sharp sand or building sand.
• Cement: Ordinary Portland Cement (OPC).
• Water: Clean water for mixing.
• Mixing Container: A bucket, wheelbarrow, or mortar board.
• Mixing Tools: Shovel, trowel, or mechanical mixer.
• Pointing Trowel: A small trowel specifically designed for filling joints.
• Bucket Trowel: Useful for scooping mix.
• Stiff Brush: For cleaning excess mortar.
• Sponge or Cloth: For final cleaning.
• Protective Gear: Gloves, safety glasses.

Step-by-Step Guide

Here are the basic steps for pointing slabs using the traditional cement method:

1. Prepare the Mix: Combine the sand and cement in the correct ratio (a common ratio is 3 parts sand to 1 part cement, but this can vary based on the type of sand and desired strength). Gradually add water while mixing thoroughly until you achieve a consistent, workable, and stiff paste-like consistency. The mix should hold its shape but still be wet enough to be pressed into the joints. Getting the water content right is crucial; too wet and it will be weak, too dry and it will be hard to work.
2. Prepare the Joints: Ensure the gaps between the slabs are clean and free of dirt, debris, and loose material. The joints should ideally be wet before you start pointing to prevent the slabs from drawing water out of the mortar too quickly.
3. Apply the Mix: Using a pointing trowel or bucket trowel, scoop a manageable amount of the cement mix. Press the mix firmly into the gaps between the slabs. Work your way along each joint, ensuring the mix fills the gap completely from top to bottom. As mentioned in the reference, this involves filling one joint at a time.
4. Compact and Finish: As you fill the joints, use the pointing trowel to compact the mix, ensuring there are no air pockets. Smooth the surface of the joint to match the desired finish (e.g., flush with the slab surface, slightly recessed).
5. Clean Up: Once the mortar has started to firm up but is not fully set (usually within 30 minutes to an hour, depending on conditions), use a stiff brush to gently brush away any excess mortar from the surface of the slabs. Prompt cleaning is essential as hardened cement is very difficult to remove from paving. A damp sponge can be used for final cleaning around the joint edges.

Tips for Success

• Get the Mix Ratio Right: As highlighted in the reference, the correct ratio of sand, cement, and water is vital for strength and workability.
• Work in Sections: Pointing is best done in smaller sections, especially in warm weather, to prevent the mix from drying out before you can finish and clean.
• Keep Tools Clean: Regularly clean your trowels and mixing equipment to prevent mortar build-up.
• Proper Curing: Keep the joints damp for a few days after pointing to allow the cement to cure properly and achieve maximum strength. Avoid heavy traffic on the area until the mortar is fully set (usually several days).