1: If weeds have previously grown in the paving, it is important to remove all weed or kill it off using a suitable environmentally-friendly weed killer. New filling material cannot fight existing weeds that have taken root in the joints or under the paving. 

2: Remove the old filling material. Use either a joint-cleaning tool and stiff broom or a high-pressure cleaner. Clear the joints to a depth of at least 30 mm. When using a high-pressure cleaner, avoid damaging the paving stones/flagstones and underlying foundation.

3: Clean the paving stones with water. They will usually become soiled when you remove the old joint-filling material. An industrial vacuum cleaner can also be used to remove old joint-filling material.

4: The paving stones must be completely dry before filling the joints.

5: Brush the filling material down into the joints. For best results, brush diagonally and along the line of the joints. If possible, use a pneumatic compactor.

6: Check the joint filling using a trowel. If the joints are filled properly, you can only press the trowel a few millimetres into the joint.

7: If the joints are not properly filled, brush more filling material down into them.

8: To finish, use a soft brush to ensure all of the joints are filled and clear any excess filling material. Cover and store any excess filling material in a dry location for later use.

9: Congratulations! You now have attractive and welcoming joints that inhibit the growth of weeds. Remember to refill joints as necessary.