Mortar fails before brick does. By the time you see crumbling joints, your wall has been shedding water into the structure for years. Repointing mortar is the process of cutting out the deteriorated mortar between bricks and replacing it with fresh mix — and done correctly, it extends a brick wall by another 50 to 100 years. Done wrong with the wrong mortar type, it accelerates damage and traps moisture against the masonry. This guide walks through the difference.
How to Tell if Your Wall Needs Repointing
Grab a screwdriver and press it into a mortar joint. Healthy mortar resists; you can scratch the surface but not gouge it. Failing mortar crumbles, flakes, or recedes more than 1/4 inch from the brick face. Other warning signs include horizontal cracks running through joints, white efflorescence streaking down the wall, and individual bricks that move when pushed.
A 200-square-foot chimney with widespread joint failure needs full repointing. A small section showing isolated cracks may only need spot repairs. Walk the entire wall before committing to a project scope.
Choosing the Right Mortar Type
This is the most important decision you will make, and most DIYers get it wrong. Mortar comes in five types: M, S, N, O, and K, ranked by compressive strength. Type S (1,800 psi) and Type M (2,500 psi) are for new structural work — load-bearing walls, foundations, and below-grade applications. Type N (750 psi) is the standard for above-grade brick veneer and chimneys above the roofline.
Critical rule: never repoint old soft brick with modern Portland-heavy Type S or M. Pre-1930 brick is softer than the mortar will be, and the harder mortar pops the brick faces off during freeze-thaw cycles. Use Type O (350 psi) or a lime-based historic mortar for any building older than World War II. Bagged Type N from Quikrete runs about $6.50 per 60-pound bag at Home Depot; lime mortar from suppliers like Lancaster Lime Works costs $35 to $55 per bag.
Tools You Need
- Tuck-pointing grinder with a 4-inch diamond blade (Bosch CSG15 or DeWalt DWE402) — $145 to $189
- Plugging chisel and 3-pound mason’s hammer for finishing cuts
- Margin trowel and a pointing trowel (Marshalltown 5-inch)
- Mortar hawk or hand board
- Jointing tool sized to match the existing joint profile — concave, V-joint, or weather-struck
- Stiff natural-bristle brush (never wire — it stains brick)
- Spray bottle for keeping work damp
- Safety glasses, N95 respirator (silica dust is no joke), and leather gloves
Step-by-Step Process
- Mist the wall thoroughly with water the evening before and again 30 minutes before starting. Dry brick sucks moisture out of fresh mortar and causes weak, crumbly joints.
- Grind out the horizontal joints first to a depth of 3/4 to 1 inch — twice the joint width minimum. Then chisel out the vertical (head) joints with a plugging chisel. Never grind verticals — the spinning disc shoots into the brick face.
- Brush all loose material out, then vacuum joints with a shop vac. Re-mist the wall.
- Mix mortar to peanut-butter consistency. It should hold a ridge when scraped with the trowel but not be soupy. Use clean water, ideally rainwater or filtered.
- Pack mortar into the joints using a 1/2-inch or 5/8-inch tuck-pointing trowel. Press firmly to eliminate voids. Work in lifts — fill deep joints in two passes if needed.
- Wait until the mortar is thumbprint-firm (usually 30 to 90 minutes depending on temperature) before tooling. Run the jointer along each joint to compact and shape the surface.
- Brush diagonally with a natural-bristle brush after tooling to remove tags and crumbs.
- Mist twice daily for three days during cure. Skipping this step is the single biggest cause of cracked, dusty mortar.
Cost Breakdown
DIY materials run $0.85 to $1.25 per square foot of wall area in mortar, blades, and supplies. A 4-inch diamond blade lasts roughly 60 to 100 square feet before it loses bite — budget two to three blades for a chimney job. Professional repointing costs $8 to $15 per square foot in most US markets, with chimneys running $1,200 to $3,500 depending on access and height. Tall chimneys requiring scaffolding push costs to $4,500 and up.
Color Matching Old Mortar
Aged mortar is rarely pure gray. Sand color, lime content, and decades of weather give old walls warm tan, buff, or pink tones that bagged mortar does not match. Mix in masonry pigments from SureCrete or Davis Colors at 1 to 3 percent by weight of cement. Make a small test batch, let it cure for 7 days, and compare to the existing wall in dry conditions before mixing a large batch.
When to Hire a Mason
Chimneys above the roofline, anything two stories or higher, and historic homes with lime mortar belong to a professional mason. The combination of ladder work, silica exposure, and color-matching expertise makes DIY a stretch above 10 feet. For ground-level garden walls, planter boxes, and short retaining walls, repointing is a satisfying weekend project that saves real money. Budget two full days for a 100-square-foot section your first time out.
