FLUSH JOINT FINISH
As the name implies, this joint finish is flat and intended to be flush with the face of the brickwork (see Fig 163). On internal work the joints can simply be left ‘flush from the trowel’ while the bricks are being laid – this ‘rough’ finish can contain small gaps or misses and offers no weather protection if used externally. Ironing the joints with a tool made of steel will leave tool marks in the mortar so a wooden tool (200 x 50 x 12mm) with a rounded spatula-like end should be used to flatten the joints. Care must be taken to ensure that the tool does not cause the joints to look concave; they should be properly flat.
Fig. 163 Flush joint finish.
When applying this type of joint finish, timing is very important, as it is very easy to stain the face of the brickwork. If it is done too soon, the mortar will be too wet; too late and the finish will be crumbly.
On internal work, a joint left flush from the trowel can be given a very uniform and gap-free finish by rubbing the surface with a small piece of sack cloth (‘bag rubbing’). Whilst the surface finish is even, this process does expose the aggregate in the mortar as opposed to compacting the joint, so it is not recommended for external work. On large areas the sack cloth should be turned periodically and shaken out, to avoid debris staining the face of the brickwork.