Masonry repointing, tuckpointing, and restoration field guide

What repointing is

Repointing is the repair that removes the deteriorated outer mortar from masonry joints and replaces it with fresh mortar, so the wall sheds water and the units stay bedded. The mortar is the part that wears out. The brick or stone can stand for a century while the joints around it erode back, and repointing renews those joints before the water gets behind the wall and into the structure.

The work sounds simple and it is not. The single most damaging mistake in the trade is using a mortar that is harder and less vapor-open than the masonry. On soft historic brick that one decision can destroy the wall the repair was supposed to save. A Portland-cement mortar troweled into a wall of soft, low-fired brick traps moisture and stress in the units, and the faces spall off. That is the failure this guide is built around.

Doing it right means three things done together: match the new mortar to the original, cut the joints out to the proper depth without damaging the units, and tool the right profile. Lose any one and you get a repair that leaks, falls out, or wrecks the brick. The wall itself, how it is built and why it manages water rather than blocking it, is covered in the masonry construction guide, and the cracking that movement causes is covered in the building movement joint guide. Both cross this work constantly. For historic and landmark masonry, the National Park Service Preservation Brief 2 on repointing is the governing reference, and the project's preservation architect and the AHJ set the standard you build to.

Why must the new mortar be softer than the brick?

The new mortar must be softer, more vapor-open, and lower in strength than the masonry units it sits between. This is the cardinal rule of repointing, and it runs against the instinct that a stronger mix is a better mix. In a masonry wall the mortar is sacrificial on purpose. It is meant to be the weak, breathable path that takes the wear and the movement so the expensive units do not.

Water gets into every masonry wall. It has to leave somewhere, and it should leave through the joints, which are easier and cheaper to renew than the brick. A soft, vapor-open mortar lets moisture migrate out through the joint and evaporate. It also yields a little when the wall expands and contracts with heat and moisture, relieving stress at the joint instead of in the unit.

Make the mortar harder than the brick and you reverse all of that. The water can no longer leave through the joint, so it leaves through the face of the unit. The wall can no longer move at the joint, so the stress concentrates in the unit. On soft historic brick the result is spalling, and it is not reversible. For historic work, Preservation Brief 2 frames the requirement directly: the new mortar should be as soft or softer and as vapor-permeable as the historic mortar and the units. Confirm the right strength class with the preservation architect and a mortar analysis, not from habit.

The Portland-cement-on-soft-brick disaster

The classic failure in this trade has a name on every old building that got the wrong repair: spalling. A well-meaning crew points a wall of soft, hand-made brick with a hard Portland-cement mortar, the wall looks crisp and tight for a season, and then the brick faces start cracking and falling off. The mortar that was supposed to protect the wall is what destroyed it.

The mechanism is moisture and stress, both forced into the unit. Pre-war brick was fired at lower temperatures than modern brick, so it is softer, more porous, and more vapor-open. It was built to work with a soft lime mortar that breathes and moves with it. Seal that wall up with a rigid, impermeable cement mortar and the water that gets in can no longer escape through the joints. It escapes through the brick instead, and when it freezes inside the porous face the face pops off. The hard mortar also grips the unit and will not yield to seasonal movement, so the expansion the wall used to relieve at the joint now shears the brick.

Once the faces spall, the porous interior of the brick is exposed and the deterioration accelerates. The repair is no longer repointing. It is brick replacement, which is far more invasive and expensive than the joint repair that started it. This is the cautionary tale behind the softer-than-the-units rule, and it is why historic repointing is hedged so hard to Preservation Brief 2, the preservation architect, and a proper mortar analysis before the first joint is cut.

Why mortar joints fail and need repointing

Mortar joints fail because they are designed to. Mortar is sacrificial. It weathers, erodes, and gives up the surface so the units and the structure do not, and over decades the outer face of the joint washes and freezes its way back into the wall. Repointing is the planned renewal of that sacrificial layer.

Water is the driver. Rain, freeze-thaw cycling, and wind-driven moisture work the joint face loose, and once the mortar recedes far enough, water sits in the open joint and gets behind the wall. From there it reaches the cavity, the ties, the flashing, and the structure, and a joint problem becomes a wall problem. The visible tells are receding joints, mortar you can rake out with a fingernail, hairline cracks, white efflorescence where salts are leaching out, and damp showing on the interior face.

The timing matters. Repoint when the joints have eroded but before the units start to suffer, and you renew a wear layer. Wait until the brick is spalling and the wall is taking on water, and you are now into unit replacement and possible structural repair. The honest answer on extent and urgency comes from a close survey, and on historic buildings from the preservation architect's assessment, not from a glance off the sidewalk.

Matching the mortar to the original

Match the new mortar to the original, not to a bag spec or a shop default. The match is the difference between a repair that disappears into the wall and one that announces itself and, worse, behaves differently than the wall around it. On historic work the match is governed by Preservation Brief 2 and approved through the preservation architect.

There are several things to match, and they are not interchangeable. The type and strength class, so the new mortar is as soft or softer than the original. The lime content, because historic mortar was lime-rich and soft. The color, which on old work comes mostly from the sand and the lime, not from pigment. The sand, matched for color, grain size, and sharpness, because the sand is the largest ingredient and drives both the look and the texture. And the joint profile and tooling, covered later, so the finished joint reads like the rest of the wall.

The proof is a test panel. Mix the proposed mortar, point a sample area of the actual wall, let it cure, and compare it to the original before anyone commits to the whole facade. The panel gets reviewed and approved, and on a historic project that approval runs through the preservation architect and, where applicable, the AHJ. A mortar that looks right wet on the board can dry a shade off, so the cured panel on the wall is the only honest test.

Lime mortar versus Portland-cement mortar

Historic mortar is lime mortar: soft, breathable, and slow to cure, and it has a quality modern mortar does not. It self-heals. When hairline cracks open in a lime joint, moisture reactivates the free lime, it reacts with carbon dioxide in the air, and the calcium carbonate that forms re-cements the crack over time. Lime mortar also stays vapor-open, so the wall breathes and water leaves through the joint as intended.

Modern Portland-cement mortar is the opposite character: hard, fast-setting, strong, and comparatively impermeable. That is exactly what you want on a hard stone pier, a foundation, or new high-fired brick that can match its strength. It is exactly what you do not want troweled into soft historic brick, for every reason in the disaster section above.

The right binder follows the wall. ASTM C270 defines mortar by type, from the high-strength M and S down through N to the soft, lime-rich Type O, with the very soft Type K carried in an appendix and straight lime-sand mortars used on the softest masonry. Type O and the lime-rich mixes have low compressive strength by design, on the order of a few hundred psi, which is what makes them compatible with soft units. The correct type for a given wall depends on the units and the original mortar, so confirm the mix with a mortar analysis and the preservation architect rather than reaching for a familiar bag.

Analyzing the existing mortar

Before you can match the mortar you have to know what is in it. The existing mortar gets analyzed, by laboratory test or by careful visual and physical examination, to establish the binder, the sand, and the proportions. A lab can characterize the binder type and ratio and recover the sand for matching. A skilled visual analysis can read a great deal from a clean sample, the color and grade of the sand chief among them.

The sand is the key recovery. Take a sound mortar sample from a protected part of the wall, break down the binder, and you are left with the original sand, which you match for color, grain size, and sharpness. Get the sand right and most of the color comes with it, because in historic mortar the sand and the lime are the color. Pigment is the last and smallest correction, not the first move.

The analysis sets the target; the test panel proves you hit it. Mix to the analyzed proportions, point a sample on the wall, cure it, and compare. On historic and landmark work this whole sequence, analysis, mix design, and approved test panel, runs through the preservation architect and Preservation Brief 2, and it is approved before the production work starts, not after.

Assessing the wall before you start

Repointing starts with a survey, not a grinder. Walk the wall close, ideally off a lift or scaffold, and read the actual condition of the joints, the units, and the details above. The assessment decides how much work the wall needs and whether repointing alone will hold.

Sort the extent first. Some walls need spot repointing where only failed areas get cut and filled, blended into sound original joints. Others have lost the mortar broadly enough to need full repointing of an elevation. Cutting good mortar out needlessly is its own damage, so you point what has failed, not the whole wall by reflex, unless the survey shows it.

Then find the cause, because repointing treats the symptom and the cause is usually above. Look for the water source: a failed coping or cap, missing or rusted flashing, a clogged or leaking gutter, a cracked sill, a bad downspout. Check the units for spalling and cracking that signal a past hard-mortar repair, and look for structural movement, bulging, displaced units, or stair-step cracking, that points past pointing into engineering. Where there is real movement or doubt, that is a call for a structural engineer and, on historic work, the preservation architect, before any mortar is touched.

Cutting out the joint

The joint is raked or cut out to sound mortar at the proper depth without widening it or damaging the units. This is the prep that makes or breaks the repair, and it is where impatience does the most harm. The goal is a clean, square-backed slot of consistent depth into which fresh mortar can key, with the surrounding brick or stone untouched.

On soft historic masonry the work is done by hand. A plugging chisel and a mortar rake worked carefully take the old mortar out without the vibration and edge damage a power tool causes. It is slower and it is the right method, because the units are softer than the tools and the saw. On hard modern brick with wide, regular joints a saw or grinder can be used to start the cut, but only with skill and great care, and the corners and joint backs are always finished by hand.

Two rules hold throughout. Do not widen the joint, because a wider joint changes the look and the structure of the wall and exposes more brick edge to damage. And do not cut into the units. The brick arris, the sharp edge of the face, is the part that chips first and the part you can never put back. Where a saw is used at all on historic fabric, it is the exception that the preservation architect signs off on, not the default.

How deep do you cut out a mortar joint?

Cut the joint out to roughly 2 to 2.5 times its width, to a clean square back against sound mortar. For typical joints that lands around 5/8 to 3/4 in as a practical minimum, and wider joints go deeper in proportion. This depth is the common guidance carried in Preservation Brief 2 and the mortar standards, and it exists for a mechanical reason.

Too shallow and the new mortar has nothing to key into. A thin skim of fresh mortar over a shallow cut has no depth of bond, so it shrinks, debonds, and falls out within a few seasons, and you have repointed the wall for nothing. Too deep is its own problem on most walls, disturbing sound mortar and the bed unnecessarily and making full compaction harder. The target is into sound mortar and no further, at the 2 to 2.5 times width rule of thumb.

Cut to a square back, not a feathered V. A square-backed joint gives the fresh mortar a face to bear against and pack into. A tapered cut leaves a thin edge of new mortar at the back that cannot compact and becomes the first thing to fail. Confirm the depth and the back profile against the project specification and, on historic work, the preservation architect's direction.

The angle-grinder and saw caution

The angle grinder is the fastest way to ruin a historic wall, and it is everywhere because it is fast and cheap. On soft, old brick a spinning diamond blade does two things that are very hard to undo: it cuts into the brick edges, and it widens the joint. Both are permanent damage to the exact fabric the repair was meant to preserve.

The blade does not stay in the joint. It rides up onto the brick arris and shaves it, it wanders off the line of an irregular hand-laid joint, and the vibration alone can crack the face of a soft unit. The bed joints suffer worst, because a circular blade run along a thin horizontal joint overcuts into the brick above and below. What you are left with is a wall of widened joints with sawn brick edges, and no mortar match can hide that.

On soft historic masonry, hand-raking is the method, full stop. On hard modern brick with wide uniform joints a saw may be used to start the vertical cuts by a skilled hand, with the bed joints and all corners finished by chisel, but that is a deliberate decision, not a shortcut applied to every wall. The skill is knowing when the saw has any place at all, and on landmark work that call goes through the preservation architect.

Cleaning and pre-wetting the joint

Once the joints are cut, clean and pre-wet them before any mortar goes in. Brush and blow the slot out so no dust, loose grit, or mortar fins remain, because fresh mortar cannot bond to dust. Any fins left by a saw on the top and bottom brick get knocked off so the new mortar bonds directly to the unit.

Then pre-wet. Dry masonry is thirsty, and if you pack fresh mortar into a dry joint the brick pulls the water straight out of the mix before it can cure. The mortar dries instead of curing, never gains strength, shrinks, and debonds. Dampen the joint and the surrounding masonry with clean water ahead of pointing so the wall is damp but not running wet, with no standing water in the joint.

Timing the pre-wet matters more with lime-rich mortar, which depends on slow curing and is unforgiving of a dry, sucking substrate. On a hot or windy day the wall dries fast, so you wet again as you go and keep the working area damp. Pack mortar into a thirsty wall in summer and you will watch the joints fail by fall.

Filling the joint in lifts

Fill the joint in thin layers, called lifts, not in one shot. Pack mortar to the back of the slot first, then build it forward in lifts of roughly 1/4 in, letting each layer firm up before the next goes on. This is how you get a full-depth, void-free joint that bonds at every level instead of a face plug with hollow behind it.

Compaction is the whole point. Each lift gets pressed hard into the joint with the pointing iron so it keys against the back and the sides and against the lift below, driving out voids. A joint filled in one deep pass cannot be compacted at the back, so it traps air pockets and shrinks unevenly, and those voids are where water collects and freezes later. Thin lifts, well compacted, give a dense joint the full depth of the cut.

Work tight and keep the face clean. Use a pointing iron or slicker sized to the joint, hawk the mortar up to the wall, and press it in without smearing the brick faces, because mortar dragged across soft historic brick stains it and is hard to clean off without further damage. Fill flush or slightly proud for now. The final profile is tooled later, once the mortar has firmed to the right point.

Tooling the joint to the profile

Tool the joint when the mortar has reached thumbprint hardness: firm enough to hold an impression without sticking to the iron or smearing. Tool too soon and you drag a wet, weak surface; tool too late and the mortar has set and will not compress. The window is real and it shifts with the weather, so you watch the joints rather than the clock.

Tooling does two jobs. It shapes the joint to match the original profile so the repair reads like the rest of the wall, and it compresses the surface of the mortar, which densifies the outer skin and closes it against water. That compressed skin is a big part of why a properly tooled concave joint sheds water and an untooled or overworked joint does not. Strike the profile with the right tool for the shape and let the burrs cure before brushing them off.

Match the original profile, not a profile you prefer. A wall tooled flush or struck a certain way was built that way for a reason, often to shed water in that climate, and changing it changes both the look and the performance. On historic work the profile is part of the character and is approved through the preservation architect and Preservation Brief 2.

Joint profiles and which sheds water

The joint profile is the finished shape of the mortar face, and it controls both the appearance and how the joint handles water. The common profiles are concave, flush, weathered or weather-struck, and raked, and they do not perform the same in the weather.

Concave is the one most exposed walls want. The iron-struck half-round packs the surface dense and sheds water, and it forgives the small irregularities of hand-laid brick, which is why it is the default for durability on weather-facing masonry. Weather-struck, angled so the joint sheds outward and downward, also handles water well when struck correctly, with the recess at the top of the joint kept shallow. Flush sits even with the face and is common on historic and stone work but does not compress or shed as aggressively. Raked, recessed back from the face, looks crisp and is the worst for weather because it creates a ledge that holds water and exposes more joint, so it belongs on protected interior or low-exposure work, not on a parapet or a rain-driven elevation.

On restoration the choice is usually made for you: match what is there. Where a wall is being upgraded for exposure, a switch toward concave is a judgment call that, on historic fabric, runs through the preservation architect rather than the crew's preference.

Tuckpointing versus repointing

The two terms get used as if they mean the same thing, and on most jobsites today they do. Strictly, they do not. Repointing is the repair: cutting out failed mortar and replacing it. Tuckpointing is a decorative technique, developed in England in the late 1700s, that uses two colors of mortar to fake the look of fine, precise joints, with a body mortar matched to the brick and a thin contrasting fillet ribbon set into it to read as a crisp narrow line.

In common North American usage tuckpointing has drifted to mean the same thing as repointing, the mortar-joint repair, and that is how most clients and many contractors use the word. There is no point fighting it on a sales call. It is worth knowing the real distinction, because on a historic building that actually has true tuckpointing, the decorative ribbon is part of the character and reproducing it is specialized work that the preservation architect will want matched, not replaced with a plain joint.

Replacing spalled and broken units

Where brick or stone has spalled, cracked through, or crumbled, repointing alone will not save it and the unit gets replaced. The art is matching the replacement to the original and removing the failed unit without harming its neighbors. On soft historic brick, salvaged units from a hidden part of the same building are the best match, because nothing modern matches old brick exactly in size, color, and texture.

Take the failed unit out by hand, cutting and raking the surrounding joints so the brick can be worked free without prying against the sound units around it. A stone unit cut to patch a damaged area, a Dutchman, is the same idea in stone: a matched piece let into a sound surround. Set the replacement in mortar matched to the wall, soft enough for the units, and point it to the same profile so it disappears into the elevation.

Matching is harder than it sounds and partial replacement scattered across a wall can look worse than the spalling did. On historic work the source of the replacement units, salvage versus reproduction, and the extent of replacement are decisions for the preservation architect, and significant unit loss can signal a structural or water problem that needs an engineer before the patching starts.

Crack repair and stitching

Cracks in masonry split into two questions: is the crack cosmetic or structural, and is it still moving? A fine, stable crack in a joint can be repointed. A crack that runs through units, steps diagonally across the wall, or keeps opening is telling you the wall is moving, and pointing over it just hides the symptom until it cracks again.

For non-structural cracking that needs more than mortar, masonry can be stitched. Helical stainless bars are bedded into slots cut in the bed joints and run a foot or more each side of the crack, tying the cracked sections back together and spreading the load across sound masonry, then the slots are repointed to hide the repair. Corroded or missing wall ties that let a veneer bulge can be replaced with retrofit helical ties driven into the backup.

Stitching treats the crack, not the cause. If the wall is cracking because it has no room to move, the answer is a movement joint, which is its own subject covered in the building movement joint guide. And if the cracking is structural, displacement, bulging, foundation movement, that is an engineer's call before any cosmetic repair, on historic work alongside the preservation architect.

Cleaning the masonry

Cleaning is often part of a restoration, and the rule that governs it is the gentlest method that works. The National Park Service frames this directly in Preservation Brief 1 on cleaning and water-repellent treatments: start with the least aggressive approach and step up only if you must, because the harsh methods that come easy are the ones that damage the wall.

The hazards are specific. Acid cleaners etch and dissolve acid-sensitive stone like limestone and marble and can burn soft brick, and they can drive salts into the wall that bloom back out later. High-pressure water blasting is abrasive enough to erode soft brick faces and the joints, and water cleaning in cold weather can freeze inside the masonry and spall it, the same freeze damage repointing is meant to prevent. Sandblasting is the worst of all on historic brick, because it strips the hard fired skin off the face and leaves the soft, porous interior exposed to weather, and that damage is permanent.

Test before you commit. Clean a sample area with the proposed method, let it dry, and judge the result against an untouched area before doing the whole wall. On historic fabric the method is approved through the preservation architect, and testing is not optional.

Fixing the water source above

Repointing that does not fix the water source above is repointing you will do again. Find where the water is getting in before you fill a joint, because the failed mortar at eye level is usually the symptom of a problem higher up, and fresh mortar under a leaking source erodes just as fast as the mortar it replaced.

The usual culprits are at the top of the wall and the openings. A failed or missing coping or chimney cap lets water straight into the wall head. Rusted, cracked, or absent flashing dumps water into the masonry instead of out of it. A clogged or leaking gutter, an overflowing downspout, a cracked sill, or a failed parapet all feed water into the wall that no amount of pointing below will stop. The flashing and weep details that are supposed to drain a masonry wall are covered in the masonry construction guide, and when they are gone the wall cannot manage its water no matter how good the joints are.

Fix the source first, or at least in the same campaign as the pointing. A durable repointing job sits below a watertight coping, sound flashing, and working drainage. Skip that and you have bought a few years, not a repair.

The water-repellent and sealer caution

Sealing a historic masonry wall with a water-repellent coating is a common instinct and usually the wrong move. The logic seems sound, keep the water out by coating the face, but it works against the way a masonry wall actually handles moisture, and on a soft, vapor-open wall it can do real harm.

Water gets into masonry from many directions, not just the face, and a wall has to let that moisture evaporate back out. Coat the face with a repellent that blocks vapor and you trap moisture inside the wall, where it concentrates behind the sealed skin, freezes, and drives salt damage, and the deterioration goes undetected until the coating fails and reveals that the brick and mortar behind it have eroded. On a wall that also carries salts, a repellent that limits moisture flow can be especially damaging. Preservation Brief 1 makes the point plainly: if a historic wall is kept watertight and in good repair, a water-repellent coating should not be necessary.

The durable answer is the boring one. Keep the wall in good repair, point it with the right soft mortar, and fix the water sources above, and the wall manages its own moisture the way it was built to. Where a treatment is genuinely being considered on historic fabric, it is a vapor-permeability question for the preservation architect, not a default applied off a shelf.

Weather and curing

Mortar cures by chemistry, and the chemistry needs the right temperature and moisture to work. Point in the wrong weather and even a perfectly matched mortar fails. The working range for most repointing is moderate temperatures, commonly held above about 40°F and out of the high heat, and never with frost in the forecast while the joint is green.

Lime-rich historic mortar is the slow one. It cures by carbonation over weeks and months, not the fast hydration of a cement mortar, so it has to be kept damp and protected through that early period or it dries out and never gains strength. After pointing, keep the work damp with light misting, shade it from direct sun and drying wind, and cover it from rain that would wash a green joint. In cold weather the joint has to be protected from freezing until it has cured enough to resist it, because a mortar that freezes while green is permanently weakened.

Heat is the quieter enemy. A hot, windy day pulls water out of the mortar and the wall faster than the mortar can cure, so on those days you pre-wet more, work smaller areas, and keep the new joints damp. Rush the cure in summer and you get the same dusting, debonding joints you would get from a winter freeze.

What to record

Repointing is a repair that has to be defensible years later, when the only question is whether the mortar that went into the wall was the right mortar. The record is what answers it, and on a historic project the documentation is part of the deliverable, not an afterthought. The mortar analysis, the approved mix, the test panel, the extent of work, the profile, and dated photos before, during, and after, all belong in the file.

A field tool that captures this on the wall is worth more than a binder filled out later from memory. With FieldOS the crew can photograph each elevation before cutting, log the approved mix and the cut-out depth, tag the test-panel location and its approval, and attach the after photos to the same record, so the package the preservation architect and the owner need is built as the work happens. The point is a record that ties the mortar in the wall to the analysis and the approval that justified it.

Record enough that a stranger could reproduce the decision: the analyzed original mortar, the matched mix and proportions, the sand source, the cut-out depth, the joint profile, the extent pointed versus left original, and who approved the panel.

Common mistakes

• Using Portland-cement or any too-hard mortar on soft historic brick, which traps moisture and stress and spalls the faces off.
• Saw-cutting or grinding joints on soft masonry, which widens the joint and damages the brick edges permanently.
• Cutting the joint out too shallow, so the new mortar has no depth to key into and falls out within a few seasons.
• Skipping the mortar analysis and test panel, so the color, sand, and strength do not match the original.
• Tooling the wrong profile, or changing it from the original, which alters both the look and how the joint sheds water.
• Repointing without finding and fixing the water source above, so fresh joints erode under the same leak.
• Sealing a water-repellent coating over a wall that already holds moisture, trapping it and accelerating decay.

Field checklist

Standards and references

For historic and landmark masonry the controlling reference is the National Park Service Preservation Brief 2, Repointing Mortar Joints in Historic Masonry Buildings. It frames the whole job: match the original mortar, make the new mortar as soft or softer and as vapor-permeable as the original and the units, cut the joints to depth without damaging the masonry, and tool the profile to match. Preservation Brief 1 covers the related cleaning and water-repellent questions, and its rule is the gentlest method that works.

ASTM C270 is the specification behind the mortar types, M, S, N, and O, with the softer Type K in an appendix and straight lime-sand mortars for the softest work. The takeaway from C270 for restoration is to pick the type by compatibility with the units and the original mortar, not by maximum strength, and to confirm it against a mortar analysis. The 2 to 2.5 times width cut-out depth and the matching, depth, and profile decisions all defer to Brief 2 and, on a given project, to the preservation architect's specification.

Two things outrank the rules of thumb. The preservation architect or conservator sets the approved mortar, depth, and profile for the building, through the analysis and the test panel. And the AHJ governs historic-district and landmark work and any permits. Cite the standard that controls the point, hedge the mortar, depth, and profile to Brief 2 and the preservation architect, and treat the softer-than-the-units rule and the fix-the-water-source rule as the two you do not bend.

Terms and definitions

Repointing carries a handful of terms that get used loosely, and on a historic job the precise meaning matters because it changes what gets approved and built.

Knowing the difference between repointing and true tuckpointing, between a sacrificial soft mortar and a hard cement one, and between matching the original and defaulting to a bag, is most of what separates a restoration mason from a tourist with a grinder.

Repointing

Removing deteriorated outer mortar from joints and replacing it with fresh, compatible mortar

Tuckpointing

Strictly, a decorative two-color technique faking fine joints; in common usage, a synonym for repointing

Sacrificial mortar

Mortar kept softer and more vapor-open than the units so it takes the wear and lets the wall breathe

Lime vs Portland mortar

Soft, breathable, self-healing lime mortar for historic units versus hard, impermeable Portland-cement mortar

Mortar matching

Matching the new mortar to the original in type, lime content, color, sand, and profile, proven by a test panel

Cut-out depth

How far the old mortar is removed, about 2 to 2.5 times the joint width, square back to sound mortar

Joint profile / tooling

The finished shape of the joint, struck at thumbprint hardness to match the original and shed water

Spalling

Cracking and flaking of unit faces, the classic damage from trapping moisture and stress with too-hard mortar

NPS Preservation Brief 2

The National Park Service guidance on repointing mortar joints in historic masonry buildings

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