How to Fix Crumbling Chimney Mortar

By eHow Home & Garden Editor

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Avoid extensive, costly damage to a masonry chimney. Maintain the mortar joints by tuck-pointing (repointing) them, and make sure the chimney crown remains sealed against water.

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Instructions

Difficulty: Challenging

Things You’ll Need:

Crown Repair And Sealing Material
Jointing Tool
Brick Trowel
Mortar Mix
Soft Brush
Cement-mixing Container And Hoe
Grinder With Tuck-pointing Attachment And Blades
High-temperature Caulk And Caulking Gun
Ladders Or Scaffolding
Mason's Hammer And Chisel
Pointing Trowel
Scraper
Square Mason's Trowel Or Board

Tuck-pointing masonry joints

Step1

Work from the bottom up to remove loose mortar a few feet (a meter or so) at a time. Set up ladders or scaffolding if necessary. Use a mason's hammer and chisel, a scraper and similar hand tools for difficult-to-reach areas. For extensive tuck-pointing, rent an electric grinder with a tuck-pointing attachment and blades.

Step2

Mix water into a packaged mortar mix as directed on the label, using a cement-mixing container and hoe.

Step3

Apply the mortar by first loading the bottom side of a square mason's trowel (or a board) with mortar (see A). Then, holding the trowel against the chimney just below the joint you're filling, slice off a portion of the mortar with a pointing trowel and pack it into the joint.

Step4

When the joints in an area are all full, strike off the excess by slicing through the mortar with a brick trowel held flat against the bricks.

Step5

Compress, shape and smooth the joint. Run a jointing tool across the joints for concave and V joints (see B). Or use the tip of a pointing trowel to create a 30-degree bevel from the underside of the upper course to the edge of the lower course. Knock off any excess and move up to the next section.

Step6

When the joints have set up, clean the face of the brick with a soft brush.

Repairing a chimney crown

Step1

If a traditional crown made of portland cement and sand is badly eroded or cracked, replace it with a modern (crown-sealer) system. These coatings, which you can apply with a trowel (following the manufacturer's instructions), remain flexible and provide a far superior water seal. If the crown has some cracks and is beginning to show wear, or even if a masonry crown is in good condition, consider using this material as part of an overall chimney repair.

Step2

Seal joints between the clay flue's liner and the crown with high-temperature caulk.

Tips & Warnings

For very minor tuck-pointing repairs, use mortar-patching material in caulking-gun cartridges.
Exercise caution and follow proper safety procedures when working on a ladder or scaffolding.