How to Fix Crumbling Mortar Joints the Right Way (2024)

TL;DR: Mortar joints that have crumbled more than a quarter-inch deep need to be raked out and repointed, not just skimmed over with new mortar. Use a mortar mix matched to your home's age (Type N for most houses built after 1900, softer lime-based mixes for anything older), and let each joint cure for 3-7 days before it gets wet. DIY repointing runs $0 in labor but costs $20-$40 in tools and materials per 10 square feet; hiring a mason typically runs $8-$25 per square foot.

_Last reviewed: July 2026 · 8 min read_

Chalky, cracked, or missing mortar between your bricks isn't just an eyesore. It's a sign water is getting into the wall assembly, and once that starts, freeze-thaw cycles will pop bricks loose faster than you'd expect. The good news is that fixing it correctly isn't complicated, it just requires the right mortar, the right depth, and patience you probably don't want to give it.

Okoniq Property Hub keeps a running log of exterior repairs like this one, so you know exactly when a wall was last repointed and which mortar mix was used.

How do you know if mortar joints actually need repair?

Press a key or screwdriver into the joint. If it crumbles more than a quarter-inch deep, or if you can see daylight through a joint from inside, it's past the point of cosmetic fixing. Surface chalking or minor hairline cracking is normal weathering and doesn't need intervention yet.

Look for a pattern too. Mortar failing only on the north-facing wall usually means shade and slow drying are the culprit. Failing mostly near the roofline or a chimney often points to water intrusion from above, which is worth checking against signs your roof is aging faster than it should before you touch the mortar at all. Fixing joints while water keeps pouring in from a bad flashing detail is wasted work.

What's the right way to remove old, crumbling mortar?

Rake it out to a depth of at least two to two-and-a-half times the joint width, using a grinder with a diamond blade for straight cuts or a mortar rake for tighter joints, then finish by hand with a chisel so you don't nick the brick edges. Going too shallow is the single most common DIY mistake: new mortar skimmed over old crumbling mortar will pop off again within a season or two because it has nothing solid to bond to.

Clean the joint out with a stiff brush and rinse with water before repointing. Dust and debris left in the cavity weaken the bond just as much as insufficient depth does. If you're working near ground level and notice the crumbling coincides with damp soil or standing water against the foundation, check for signs of a slab leak under your floor first, since a leak feeding that wall will undo your repointing job regardless of how well it's done.

What mortar mix should you actually use?

Match the mortar to the house, not just the brick color. Homes built before roughly 1930 typically used lime-based mortar that's softer than the brick itself, letting the wall flex and breathe. Modern portland-cement mortars (Type N or Type S) are harder and, if used on an old lime-mortar house, will actually crack the brick because the mortar won't give.

| Home Age | Recommended Mix | Compressive Strength | Notes | |---|---|---|---| | Pre-1930 | Lime-based / Type O | ~350 psi | Softer than brick, allows movement | | 1930-1980 | Type N | ~750 psi | Standard for most residential brick | | Post-1980 / structural | Type S | ~1,800 psi | Load-bearing walls, foundations |

Mix small batches, roughly what you'll use in 30-45 minutes, since mortar starts setting up and loses workability fast. Pack it into the joint in thin layers rather than one thick fill; this compresses the mortar and reduces voids that lead to early failure.

How long does repointed mortar need to cure, and what should you avoid afterward?

Give fresh mortar 3-7 days of protection from rain and direct sun before it's exposed to normal weather, and a full 28 days before it reaches close to final strength. Tenting the area with plastic sheeting in hot or rainy weather prevents the mortar from drying too fast or washing out before it sets.

Avoid pressure washing the wall for at least a year after repointing, and skip any waterproof "brick sealer" products on lime-mortar homes entirely, they trap moisture that the wall needs to release and accelerate the exact deterioration you just fixed. If the crumbling was concentrated around gutters or downspouts, it's worth checking signs water is getting behind your gutters, since chronic overflow is one of the most common hidden causes of localized mortar failure at the top of a wall.

Should you DIY this or hire a mason?

Small, ground-level jobs under 20 square feet are reasonable DIY territory if you're comfortable with a grinder and have a weekend to spare; expect to spend $20-$40 in tools and mortar for every 10 square feet. Anything above the first story, on a chimney, or covering more than a few hundred square feet is worth pricing out with a professional, both for safety and because matching mortar color and joint profile across a large repointing job takes real experience.

Professional repointing typically runs $8-$25 per square foot depending on region and access, with chimney work often priced separately at $500-$1,500 for a full repoint. If you're already vetting contractors for roof or exterior work, the same due diligence applies here: check licensing, insurance, and ask for references, similar to the approach in questions to ask before hiring a roofer.

FAQ

How much does it cost to repoint a whole house?

For a typical 1,500-2,000 square foot brick home, full repointing runs roughly $5,000-$15,000 depending on wall height, access, and region, though partial repointing of just the deteriorated sections is usually far cheaper.

Can you patch mortar without removing the old material?

No, patching over crumbling mortar without raking it out first almost always fails within one to two years because the new mortar has no solid surface to bond to.

How do you match old mortar color?

Mix a small test batch, let it cure fully for a week since mortar lightens as it dries, then compare it against the existing joints in daylight; masonry supply stores can also color-match with pigment additives if the existing mortar is unusual.

Is crumbling mortar a structural problem?

Usually not immediately, since brick veneer mortar mainly keeps water out rather than bearing load, but on older solid masonry walls extensive crumbling can eventually affect structural integrity and should be assessed by a mason.

What causes mortar to crumble in the first place?

The most common causes are water intrusion from roofing or gutter failures, using a mortar mix too hard for the brick, freeze-thaw cycling in colder climates, and simple age, since most mortar has a useful life of 25-50 years before it needs attention.

This is educational information, not structural or engineering advice. Call a licensed mason or structural engineer if you're unsure whether the deterioration affects your wall's integrity.