IT DEPENDS ON THE COMPATIBILITY OF THE NEW AND OLD BRICKS.
FROM YOUR DESCRIPTION, I ASSUME THAT THE NEW BRICKS ARE ENGINEERING TYPE. (FROST AND WATERPROOF).
THIS TYPE OF BRICK IS EXTREMELY HARD AND BRITTLE AND NOT ABLE TO WITHSTAND THE STRUCTURAL MOVEMENTS THAT A SOFTER BRICK CAN WHEN COUPLED TOGETHER AND WITH THE DIFFERENT MORTAR RATIOS REQUIRED CAN MAKE FOR FAILURE AT JOINTS.
IF THEY ARN'T COMPATIBLE WITH EXISTING BRICKS THEN THEY MOST LIKELY SHOULD NOT BE BRICK BONDED BUT COULD BE TIED IN USING A FURFIX PROFILE FLANGE AND CLIP SYSTEM WHICH WILL ALLOW FOR STRUCTURAL MOVEMENT BUT STILL TIE STRUCTURES TOGETHER.
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