Here is the definition of repointing: Repointing is the process of renewing the “pointing”, which is the external part of mortar joints, in masonry construction. Over time, weathering and decay cause voids in the joints between masonry units, usually in bricks, allowing the undesirable entrance of water. Water entering through these voids can cause significant damage through frost weathering and from salt dissolution and deposition. Repointing is also called pointing, or pointing up, although these terms more properly refer to the finishing step in new construction.
Here is the definition of tuck-pointing: Tuck-pointing is a way of using two contrasting colors of mortar in the mortar joints of brickwork, one color matching the bricks themselves, to give an artificial impression that very fine joints have been made. In some parts of the United States and Canada, some confusion may result as the term is often used interchangeably with “pointing” (to correct defects or finish off joints in newly laid masonry) and “repointing” (to place wet mortar into cut or raked joints to repair weathered joints in old masonry).
As you can see, many people use the words interchangeably. For the sake of knowing what most of Chicagoans and those in it’s numerous suburbs call it, I will use the term “tuck-pointing” from here on out.
Tuck-pointing is needed when your mortar joints (or mortar bonds) begin: falling, splitting, cracking, or deteriorating to any extent. If you notice this, it is imperative to have it corrected immediately, because if you put it off – it will cost much more down the line because you will need a chimney rebuild.
When tuck-pointing is needed, there are a few crucial steps to insure it’s longevity:
1. Grind out all spots in need of tuck-pointing with a high powered grinder, to no less than 3/4’s of an inch.
2. Brush and/or wash area of all excess mortar, sand and dust; completely cleaning off joints to be tuck-pointed.
3. Use proper mortar mix and water combination.
4. Fill joints with new mortar using proper tools.
5. Wait for the appropriate time and then strike the joints.
6. Brush off any loose mortar from bricks and/or mortar joints.