How to repair mortar joints in brick walls and chimneys

You repair failing mortar joints by repointing them. That means raking out the old crumbling mortar to a depth of about twice the joint width, brushing the joint clean, then packing in fresh mortar and tooling it to match the old profile. Matching the mortar is the part people get wrong. Old brick wants a soft lime-based mortar, and the wrong hard mix can crack the brick face over a few NH winters.

Here is the plain version. Mortar is the soft stuff between the bricks. It is meant to wear before the brick does. When it gets soft, sandy, or you can dig it out with a key, the joint has lost its grip. Water gets in. Then frost. NH frost heave pushes and pulls at anything that holds water, and a few freeze-thaw cycles will open the joint wider every year.

So you stop the water and rebuild the joint.

Grind or chisel the bad mortar out. Go about twice as deep as the joint is wide, and stop at solid mortar. Do not gouge the brick. Then blow and brush the dust out, and dampen the joint so the brick does not steal water from the new mortar. Pack the fresh mortar in tight layers. Tool it flat or concave to shed water. Let it cure slow. Keep it damp for a couple days in dry heat.

For a chimney it is the same idea with higher stakes. A chimney takes weather on all four sides plus heat from inside, so the joints fail faster up top. The crown (the concrete cap), the flashing where the chimney meets the roof, and the top courses of brick are where leaks start. If water is getting into your basement or up the chimney chase, the fix often starts at the top, not the bottom.

Cost comes down to how much joint length is failing, how high off the ground it sits, whether you need staging or a lift, and how soft the original mortar was. A few feet of joint at eye level is a small job. A full chimney rebuild above the roofline is not.

Now the part we owe you plainly. Repointing brick and rebuilding a chimney is masonry work. We are a foundation and basement crew, not a brick and chimney crew. So if the question is “who fixes my chimney mortar,” that is a mason, and you do not need us for it. We will say so straight.

Where we DO come in is when that brick is part of your foundation, or when the water that ruined the mortar is also showing up in your basement. A brick or stone foundation wall with washed-out joints is a structural problem, and that is our lane. We stabilize and repair foundation walls. We do crack injection, carbon-fiber straps, a power brace, helical or push piers, lally columns for floor support, and sister (auxiliary) wall builds. See our structural and foundation repair and foundation repair pages.

A few price markers for the foundation side, so you know the range before we ever show up. Foundation crack injection runs $1,000 to $3,000. Carbon-fiber straps run $850 each. A power brace runs $1,300 per brace. Helical piers run $2,700 per pier for the first three, then $2,200 per pier after that. A lally column or floor support runs $1,300 to $2,500. An auxiliary (sister) wall runs about $1,350 per linear foot. For a full foundation-wall rebuild or replacement, there is no flat number. We price that after we see it.

One more thing worth saying. If the mortar failed because water keeps pooling against the wall, repointing alone will not hold. That water is sitting in the disturbed backfill around your house, the looser fill that went back in when the place was built. It drains slow and holds water against the wall. Fix the joint without fixing the water and you will be back at it. If the wet is reaching your basement, the durable fix is interior drainage. See basement waterproofing and the Forever Dry System.

The brick masonry itself, though? Call a mason. We would rather point you to the right trade than sell you the wrong fix.

Want us to look at the foundation and the water? Call us at 603-610-1770 or book your free inspection. Free inspection, free estimate, quote within 24 hours, and every repair we do is backed by the 603 guarantee!

Related questions

Is a brick foundation wall with bad mortar a structural problem? It can be. If joints are washed out and the wall is bowing, leaning, or cracking, that is structural and we can help. We stabilize foundation walls with carbon-fiber straps, a power brace, or a sister wall. See structural and foundation repair.

Why does my brick keep cracking after I repoint it? Usually the wrong mortar. Old brick needs a softer lime mix. A hard modern mortar will not flex with the brick through freeze-thaw, so the brick face spalls instead. Match the original mortar. That is a mason’s call.

Do you waterproof against water that ruined my mortar? Yes, when it is reaching the basement. We install interior perimeter drainage with the Forever Dry System. We do not do exterior excavation waterproofing. In our field experience that fails in about two to three years, so we go interior for a fix that lasts.

Will fixing the chimney crown stop my basement leak? Sometimes, if water is running down the chase. But basement water more often comes from the soil around the foundation. We will inspect both so you fix the real source, not a guess. Book a free inspection.