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How do I joint concrete flag paving laid using the bound method?

Mortar Jointing using a trowel.

Joint filling usually occurs 12 hours after the flags have been laid on the mortar laying course.

Press the mortar firmly into the joints using a trowel. The whole joint should be filled with a compacted mortar to within 2-3mm of the flag surface. Finish the joint using a pointing iron. Extreme care should be taken to avoid staining the flag surface with jointing mortar. Clean any spills immediately using clean water. The strength of jointing mortar required will depend on the application. Please refer to BS 7533: Part 4. As a guide, typically a 1:4 cement/sand mix is used.

Slurry Mortar Jointing

Important: To avoid staining the surface of the flags, extreme care should be taken when slurry jointing.

Slurry jointing mortars begin to set quickly allowing the paving to be cleaned shortly after jointing is complete. Determining the optimum time to allow the joints to start to set whilst still being able to remove the excess material is crucial. If left too long it will become much more difficult to clean off and there is a risk of staining the flags permanently. Temperature and humidity will also affect the setting time. On very hot days, it may be best to leave jointing until late afternoon. We would strongly advise to construct a trial panel to determine the time required.

Completely soak the entire area of flags with clean water. A suitable strength mortar slurry should be spread over the area. A squeegee should be used to move the slurry over the surface to ensure all open joints are adequately filled. As much of the excess slurry should be removed from the surface of the flags and the joints should be allowed to firm up. Once the joints have begun to firm up any jointing slurry remaining on the surface of the flags must be washed off carefully taking care not to wash material from the joints. For best results use a sponge grout roller machine. Alternatively a pressure washer can be used with care.

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