How to Mortar Walls

Mix the mortar according to the instructions on the bag. Different mortars require different amounts of water and different setting times before they're used. If you are repointing or adding mortar to an old wall, find out what type of mortar is already in the wall before you begin. Mixing modern cement-based mortar with older lime-based mortar may cause problems with uneven expansion and contraction. Don't do mortaring work in temperatures below 45 degrees F.

Apply mortar onto the brick you're about to lay. Spread an even layer over the bottom and one side of the brick. Take some mortar onto the bottom side of your trowel and slide it over the face of the brick, leaving a layer of mortar about 3/8-inch thick.

Press the brick into place and tap it down firmly with the handle of your trowel. Check for any gaps in the mortar and fill them using the point of the trowel. Check that the top of the brick is level, using a torpedo level.

Scrape the excess mortar that's been squeezed out by the brick off the face of the wall with the trowel, leaving a flat surface.

Check the wall every time you finish a course of bricks to ensure it's perfectly vertical, using a 4-foot level. A mortar wall that isn't vertical is at greater risk of damage and collapse under the force of gravity.

Set the profile of a joint when you've finished a row of bricks by making a firm, even pass over its surface with a mason's jointer. A mason's jointer is a tool that features a curved, rounded point that presses into the mortar and recesses it behind the face of the brick. Buy or rent a mason's jointer from most home-improvement or tool-rental stores. Alternatively, create flat joints by going over them with the edge of your trowel.