Grinding vs Hand-Cutting Mortar Joints: What Belongs on Chicago Brick

By Affordable Tuckpointing Pros, a Chicago tuckpointing and brick repair company in business since 1996. License number MC6337.

Direct answer

Hand-cutting with a chisel and hammer is the default, and grinding is a limited exception to it. NPS calls hand chisels and mash hammers the traditional method and says that in most instances it poses the least threat for damage to historic masonry units and produces the best final product. [1] Grinders are allowed under specific conditions: horizontal joints only, on hard portland cement mortar, cut by a skilled mason, and finished by hand. [1] On vertical joints the answer from both primary sources is no. NPS says mechanical tools should never be used on vertical joints because of the danger of slipping and cutting into the brick above or below. [1] BIA is blunter still: using a grinder on head joint mortar will not remove the full depth of material without damaging adjacent brick, and the remainder has to come out with a chisel. [2]

TL;DR

• The job is the same either way: remove old mortar to a uniform depth and place new mortar in the joint. Only the cutting tool is in question. [2]
• NPS names hand chisels and mash hammers as the traditional method and says it poses the least threat for damage and produces the best final product, while acknowledging it is labor-intensive. [1]
• NPS also says the most common method of removing mortar is power saws or grinders, and that in the hands of unskilled masons this can be disastrous for historic masonry, particularly soft brick. [1]
• On thin joints, which is most brick walls, NPS says power saws almost always damage the units by breaking the edges and by overcutting on the head, or vertical, joints. [1]
• BIA says a grinder cannot take a head joint to full depth without damaging adjacent brick, so the extra mortar left in head joints must be removed by chisel to achieve uniform depth. [2]
• Grinding is sanctioned as half a method, not a whole one. NPS says automatic tools work best in combination with hand tools, and that final removal from the sides of the joint should still be done with a hand chisel and hammer. [1]
• Damage from an abrasive wheel is not cosmetic. NPS says abrasives do not differentiate between the dirt and the masonry, can remove the outer surface, and permanently damage it. [3]
• The decision is supposed to be made before work starts. NPS says the test panel should determine the acceptability of power tools, and BIA says repointing skills should be tested and evaluated before the contractor is selected. [1] [2]

One liner: The grinder is not the villain and the chisel is not a virtue signal. The question is which joints the wheel is allowed to enter, and the answer in both standards is the horizontal ones only.

What is the difference between grinding and hand-cutting a mortar joint?

In short: Both do the same job to the same depth. One does it with an abrasive wheel spinning inside the joint, the other with a chisel struck by a hammer.

Before the tools matter, the task has to be clear, because it is the same task either way. BIA defines repointing as the process of removing damaged or deteriorated mortar to a uniform depth and placing new mortar in the joint, and notes that it is sometimes referred to as tuckpointing. [2] Nothing in that definition names a tool. The requirement is a depth and a uniformity, and any tool that delivers both is in principle acceptable. That is the honest starting point, and it is why the argument about grinders is narrower than the internet makes it sound.

The depth is specified, and it is specified twice. NPS says old mortar should be removed to a minimum depth of 2 to 2 and a half times the width of the joint, which for most brick joints works out to roughly half an inch to one inch. [1] BIA gives a minimum of twice the joint width, generally three quarters of an inch, or until sound mortar is reached. [2] Those are minimums, not targets. NPS adds that any loose or disintegrated mortar beyond that minimum depth should also be removed. [1]

Now the tools. NPS describes the traditional manner of removing old mortar as the use of hand chisels and mash hammers. [1] BIA names two acceptable options side by side: a toothing chisel or a special pointers grinder. [2] So neither source treats the grinder as forbidden equipment. What they do is attach conditions to it, and the conditions are where the disagreement between a good tuckpointing crew and a fast one actually lives.

One more piece of context sets the scene, and it comes from NPS rather than from any contractor with an axe to grind. NPS states that the most common method of removing mortar is through the use of power saws or grinders. [1] That is a description of the industry, not a recommendation. The brief then spends several paragraphs qualifying it, which tells you the qualification is the point.

So the real question is not grinder versus chisel as a matter of taste. It is which joints the wheel is allowed into, how deep it is allowed to go, and what has to happen with a hand tool after it has gone. Every serious constraint in both documents answers one of those three.

Why does the National Park Service prefer a hammer and chisel?

In short: Because it does the least damage and produces the best final product, and NPS says so in exactly those words while conceding it takes longer.

The preference is stated plainly rather than implied. NPS says that though labor-intensive, in most instances the hand chisel and mash hammer method poses the least threat for damage to historic masonry units and produces the best final product. [1] A photograph caption in the same brief repeats it in shorter form: using a hammer and masonry chisel is the least damaging and, thus, generally the preferred method of removing old mortar in preparation for repointing historic masonry. [1]

Notice what NPS does not claim. It does not say hand-cutting is harmless. It says the opposite in the preceding sentence, that although some damage may be inevitable, careful joint preparation can help limit damage to masonry units. [1] That is a more useful framing than the marketing version of this argument. Every repointing job takes something off the wall. The choice is about how much, and about whether what comes off is old mortar or brick.

It is also worth being precise about what NPS is objecting to, because the word “power” is doing less work here than people assume. NPS says small pneumatically-powered chisels generally can be used safely and effectively to remove mortar on historic buildings, as long as the masons maintain appropriate control over the equipment. [1] A pneumatic chisel is a power tool. It is explicitly endorsed. So the objection is not to electricity or to speed in the abstract.

The objection is to a rotating abrasive wheel, and specifically to what a rotating abrasive wheel does when it is a fraction of an inch from something you cannot replace. A chisel removes what the mason drives it into and stops where the mason stops it. A wheel spinning at speed carries its own momentum into whatever it meets, and the brick it meets is softer than the diamond on the blade. That distinction, rather than any general suspicion of machinery, is what runs through the rest of the brief.

The labor-intensive part is real and no one should pretend otherwise. Hand-cutting a wall takes longer than grinding one, and on a large elevation it takes substantially longer. That is the actual trade being made when a bid comes in low, and it is worth knowing you are making it.

What does a grinder actually do to brick when it goes wrong?

In short: It breaks the edges of the units and overcuts the vertical joints, and on brick that surface loss does not grow back.

NPS gives the failure mode in one sentence with no hedging. Using power saws on walls with thin joints, such as most brick walls, almost always will result in damage to the masonry units by breaking the edges and by overcutting on the head, or vertical joints. [1] The phrase worth sitting with is “almost always,” and the qualifier worth sitting with is “thin joints, such as most brick walls.” This is not a warning about exotic buildings. It is a warning about the normal case.

NPS is equally direct about who is holding the tool. The use of power tools by unskilled masons can be disastrous for historic masonry, particularly soft brick. [1] Two variables are named there, skill and the hardness of the unit, and a Chicago wall frequently supplies the second one. NPS elsewhere groups common brick with limestone and sandstone as extremely absorbent masonry needing a continual mist of water before repointing begins. [1] Common brick is the material behind and beside a great deal of Chicago face brick.

The second primary source describes what an abrasive tool does to a masonry surface in general terms, and it applies directly. NPS Preservation Brief 1 says grit blasters, grinders and sanding discs all operate by abrading material off the surface of the masonry, and that since the abrasives do not differentiate between the dirt and the masonry, they can remove the outer surface of the masonry at the same time and result in permanently damaging it. [3] It names brick specifically: brick and architectural terra cotta are fired products with a smooth, glazed surface which can be removed by abrasive blasting or grinding. [3]

The consequences listed there are not only visual. Abrasively treated masonry is left with a rough surface which tends to hold dirt and which makes future cleaning more difficult, and the process can increase the likelihood of subsurface cracking of the masonry. [3] Abrasion of sharp corners rounds them off. [3] Brief 1 also notes that mortar joints, especially those with lime mortar, can be eroded by abrasive or mechanical cleaning. [3] A wheel that skips out of a joint and runs across a brick face is doing a small, fast version of exactly this.

Here is why that matters more than it looks on a finished wall. A brick with a broken arris, the crisp edge where the face meets the joint, has permanently widened the joint at that point. The new mortar fills the widened gap, and from six feet away the wall looks pointed. What has actually happened is that the joint line has been made irregular and the fired surface protecting the brick edge has been removed, and neither can be put back. That is our judgment about the consequence, not a claim from the briefs, but it follows directly from what Brief 1 says about the fired surface being removable and not restorable. [3]

Why can a grinder never finish a head joint?

In short: A cutting wheel is round and a head joint is short, so the wheel runs out of geometry before it runs out of mortar. Both sources stop the tool at the vertical joint.

This is the single most useful sentence in either document, and it comes from BIA. Using a grinder to remove head joint mortar will not remove the full depth of material without damaging adjacent brick, and the extra mortar left in the head joints must be removed by a chisel to achieve a uniform depth. [2] Read it twice. BIA is not saying a grinder on head joints is inadvisable. It is saying the tool cannot physically complete the task, and that a chisel has to come in behind it regardless.

NPS reaches the same place from the safety and damage side. Although mechanical tools may be used safely in limited circumstances to cut out horizontal joints in preparation for repointing, they should never be used on vertical joints because of the danger of slipping and cutting into the brick above or below the vertical joint. [1] “Never” is a strong word in a document that otherwise spends its time qualifying things, and NPS spends it here.

The geometry is easy to picture once it is pointed out. A head joint in a brick wall is about the height of one brick, bounded top and bottom by the horizontal joints and left and right by brick. A circular blade entering that short slot meets its own curvature. To reach full depth in the middle of the joint, the outer edge of the wheel has to travel past the ends of the joint, and past the ends of the joint is brick. Either the cut stops short of full depth, or it goes into the units. BIA describes precisely that fork and says the first option is what you get if you want the brick intact. [2]

Now connect it to the depth requirement, because this is where a grinder-only wall quietly fails. BIA requires a uniform depth across the work. [2] NPS requires the minimum depth specifically to ensure an adequate bond and to prevent mortar popouts. [1] If the bed joints have been cut to three quarters of an inch and the head joints have been left at a quarter because the wheel could not get in, then the depth is not uniform and a portion of the wall has new mortar sitting in a cut too shallow to develop the bond the standard is asking for. The wall looks finished. Part of it is not.

And you cannot see it afterward. Once the joints are filled and tooled, cut depth is invisible from the sidewalk and invisible from a ladder. This is the reason both documents push the decision about tools to before the work starts rather than after, which is the subject of a later section here.

None of this makes the head joint an exotic detail. In a running bond wall there is a head joint every four inches or so, on every course, across the whole elevation. Whatever happens to the head joints happens to roughly half the joint length on the building.

When is grinding actually acceptable?

In short: Horizontal joints only, on hard portland cement mortar, wide and uniform, by a skilled mason, and finished by hand. Remove any one condition and the allowance lapses.

NPS grants the exception in a single carefully bounded sentence. Under certain circumstances, thin diamond-bladed grinders may be used to cut out horizontal joints only on hard portland cement mortar common to most early-20th century masonry buildings. [1] Every clause is a condition: thin blade, diamond, horizontal joints only, hard portland cement mortar. A photo caption in the same brief adds the operator: a power grinder operated correctly by a skilled mason may be used in preparation for repointing to cut wide horizontal joints typical of many early-20th century brick structures without causing damage to the brick, and the caption notes the use of protective safety equipment. [1]

The most commonly ignored condition is the last one, and it converts the grinder from a method into half a method. NPS says that usually, automatic tools most successfully remove old mortar without damaging the masonry units when they are used in combination with hand tools. [1] It then describes exactly what that combination looks like. Where horizontal joints are uniform and fairly wide, it may be possible to use a power masonry saw to assist the removal of mortar, such as by cutting along the middle of the joint, but final mortar removal from the sides of the joints still should be done with a hand chisel and hammer. [1]

That is the sanctioned technique in full. The wheel takes a relief cut down the centre of the bed joint, well away from both bricks. The chisel takes the mortar off the two faces where the joint meets the units, which is the only place a tool can damage a brick edge. A field photograph in the brief shows the same sequence on granite steps, cut out mechanically with a vacuum attached to the cutting tool to cut down on dust, with final removal of the old mortar done by hand to avoid damage to the edges of the joints. [1] The caption adds that mechanical preparation of horizontal joints by an experienced mason may sometimes be acceptable, especially where the joints are quite wide and the masonry is a very hard stone. [1]

The substrate matters as much as the tool. NPS says using any of these power tools may be more acceptable on hard stone, such as quartzite or granite, than on terracotta with its glass-like glaze, or on soft brick or stone. [1] Read against the Chicago building stock, that sentence sorts walls into two piles. A hard-fired face brick with wide, hard portland cement bed joints is near the favourable end of the range NPS describes. Soft common brick with thin joints is at the other end, and it is the case NPS singled out as almost always resulting in damage. [1]

There is also a third tool that gets left out of the argument entirely, and it deserves a mention because it dissolves the false choice. NPS says caulking cutters with diamond blades can sometimes be used successfully to cut out joints without damaging the masonry, and explains why: caulking cutters are slow, they do not rotate but vibrate at very high speeds, thus minimising the possibility of damage to masonry units. [1] The mechanism is the whole explanation. Remove the rotation and you remove the tool’s ability to run away from the joint. What is left is slow, which is the same cost hand-cutting carries.

How deep does the cut have to be, and why do NPS and BIA give different numbers?

In short: NPS says 2 to 2 and a half times the joint width. BIA says twice, generally three quarters of an inch. Both also say “until sound mortar is reached,” and that clause outranks both numbers.

The two figures are genuinely different and it is worth setting them side by side rather than picking the one that suits. NPS requires removal to a minimum depth of 2 to 2 and a half times the width of the joint, to ensure an adequate bond and to prevent mortar popouts, which for most brick joints means approximately half an inch to one inch, and for stone masonry with wide joints may mean several inches. [1] BIA requires removal to a uniform depth that is the minimum of twice the joint width, generally three quarters of an inch, or until sound mortar is reached. [2]

The gap is smaller than it looks and the reason for it is structural rather than a contradiction. NPS Preservation Brief 2 is a historic preservation document, written for buildings where the units are soft, irreplaceable and often bedded in lime mortar. BIA Technical Note 46 is a general masonry maintenance document covering the modern stock as well. The preservation standard is the more conservative of the two, which is what you would expect. BIA itself directs readers to Preservation Brief 2 when repointing for historic preservation purposes. [2] The documents are not arguing. One defers to the other for the harder case.

What matters more than the difference is the word both of them use, which is minimum. NPS follows its figure immediately with the instruction that any loose or disintegrated mortar beyond this minimum depth also should be removed. [1] BIA writes the same idea into its own requirement with the clause “or until sound mortar is reached.” [2] Neither standard describes a fixed setting. Both describe a floor, followed by a condition that can push the cut deeper on any given joint.

This is where the depth question and the tool question meet, and it is not a point either document makes explicitly. A grinder set up for a job cuts to the depth it is set to, joint after joint, because that is what a depth stop is for. The standards do not ask for a depth. They ask for a minimum depth and then for a judgment, joint by joint, about whether the mortar behind it is sound. A mason with a chisel is making that judgment continuously because the tool reports back through the handle. That inference is ours, but the two requirements it rests on are quoted above from both sources. [1] [2]

The depth also governs what happens next, which is worth knowing when you are watching work go in. NPS says that where existing mortar has been removed to a depth of greater than one inch, those deeper areas should be filled first, compacting the new mortar in several layers, with the back of the joint filled successively by applying approximately a quarter inch of mortar and packing it well into the back corners. [1] A deep cut is not a licence to fill the void in one pass.

What should a correctly prepared joint look like before new mortar goes in?

In short: Square corners at the back of the cut, no slivers of old mortar left on the brick, no dust, and damp but not wet.

There is a checkable standard for the empty joint, and it is short enough to hold in your head while you look at a wall mid-job. NPS: mortar should be removed cleanly from the masonry units, leaving square corners at the back of the cut. [1] That phrase is the quiet test of the whole tool argument. A square corner at the back of a cut is what a flat chisel edge produces. A rotating wheel produces an arc, deepest at the centre of its travel and shallowing toward each end. The requirement is written in the shape of the hand tool.

BIA covers the faces of the cut. Care must be taken not to damage the brick faces and edges, and thin slivers of mortar remaining on the brick must be removed in order to obtain good bond between the new repointing mortar and the brick. [2] Those slivers are precisely what a centre-cut relief pass leaves behind on both sides of a bed joint, which is why NPS routes the finishing work to a hand chisel and hammer. [1] The two requirements describe the same operation from opposite ends.

Then the joint has to be clean. BIA says remove all dust and debris from the joint by brushing, blowing with oil-free compressed air or rinsing with water. [2] NPS says before filling, the joints should be rinsed with a jet of water to remove all loose particles and dust. [1] Grinding generates a great deal of fine dust inside the cut, which is one reason the NPS field photograph of mechanical cutting shows a vacuum attached to the tool. [1] Dust left in a joint sits between the new mortar and the brick, in the exact plane where bond is supposed to form.

Moisture condition is the last item and it is specific. NPS says that at the time of filling, the joints should be damp, but with no standing water present, and that for masonry walls that are extremely absorbent, naming limestone, sandstone and common brick, it is recommended that a continual mist of water be applied for a few hours before repointing begins. [1] Common brick appears by name on that list, which is worth noting on a housing stock where common brick is doing a lot of the structural work behind the face.

None of these four checks requires a tool or any expertise to observe. Square backs, clean brick faces, no dust, damp not wet. If you are on site while a wall is open, that is the moment when the quality of the preparation is still visible. After the joints are filled it is not.

What should you require from a Chicago tuckpointing contractor before work starts?

In short: A test panel that decides the tool question in writing, proof the crew can run whatever is approved, and an understanding that being a good mason is not the same as being a good repointer.

BIA puts the tool risk first on the list of things to consider before undertaking a repointing project, ahead of mortar, ahead of scheduling: the potential for power tools to damage the brick surrounding the mortar being removed. [2] The second item on that same list is about people, and it is the most quietly devastating sentence in the document. Repointing operations should be performed only by qualified and experienced repointing craftspeople. An individual who is an excellent mason may not be qualified for repointing. Skills should be tested and evaluated prior to the selection of the contractor. [2]

That distinction is not a technicality. Laying new brick and cutting old joints out of a standing wall are different crafts with different failure modes, and BIA is warning you that a strong reference for one does not transfer to the other. The instruction is also actionable in a way most advice is not, because it tells you when to do the testing: before selection, not after award.

NPS supplies the mechanism for that testing. Test panels are prepared by the contractor using the same techniques that will be used on the remainder of the project, and several panel locations may be necessary to include all types of masonry, joint styles and mortar colours, preferably not on the front or other highly visible location of the building. [1] Then the decisive line: the test panel should determine the acceptability of power tools. [1] The tool question is meant to be settled by evidence from your own wall, not by the contractor’s habit and not by an argument on the phone.

NPS adds two conditions that attach if power tools are approved. Contractors should demonstrate proficiency with power tools before their use is approved. [1] And if power tools are to be permitted, the contractor should establish a quality control program to account for worker fatigue and similar variables. [1] The fatigue clause repays attention. NPS is not only saying the crew must be skilled. It is saying that skill degrades over a shift, that a grinder is unforgiving of the degradation, and that somebody has to own that on paper. The brief also states outright that using power tools without damaging the surrounding masonry units necessitates highly skilled masons experienced in working on historic masonry buildings. [1]

Translated into questions you can actually ask a bidder, it comes to four. Will you cut a test panel somewhere inconspicuous before you price the elevation. Which joints do you intend to grind and which do you intend to chisel. Who takes the head joints to full depth, and with what. And what happens to the sides of the bed joints after the relief cut. A crew that works to the standard has ready answers, because the standard already wrote them. If you want those answers in writing for your building, get in touch and we will put them in the proposal.

When does a joint need cutting at all?

In short: BIA lists the triggers. Where none of them are present, the least damaging tool is no tool, and sound joints should be left alone.

The safest grinder is the one that never comes off the truck, and there is a sourced test for when that applies. BIA lists the conditions that require repointing: mortar erosion exceeding a quarter of an inch, crumbling mortar, mortar with voids, hairline cracks in the mortar, and cracks between the brick and mortar. [2] The assessment method is equally low-tech. Visual observation of the joints, along with light scraping using a metal tool, are the common methods for determining areas where repointing may be necessary. [2]

The timescales explain why wholesale cutting of a sound elevation is the wrong instinct. BIA Table 1 estimates time to repair for brick in walls at 100 to 150 years and beyond, and for mortar in walls at 50 years and beyond. [2] Mortar is the shorter-lived component by design, so repointing is a normal event in the life of a wall, not a failure. But the ratio also means the brick is expected to outlast two or three cycles of mortar. Every cutting operation that takes material off the units is spending down an asset that was supposed to last centuries in order to service one that was always going to be replaced.

Catching the triggers early is a matter of looking regularly. BIA says periodic inspections should be performed to determine the condition of the various materials on a building, that these can be performed monthly, yearly, biennially or on any schedule deemed appropriate, and that seasonal inspection periods are recommended so the behaviour of building materials in various weather conditions can be observed. [2] Exterior surveys should be performed with binoculars to permit close-range observation of conditions on upper floors, using adjacent balconies or roof areas where available. [2] Documentation should include comments, photographs and sketches. [2]

The reason to bother is that the joint is the water route. BIA notes that moisture may penetrate brick masonry through unbonded, cracked or deteriorated mortar joints, and that where that is the case repointing is one of the most effective ways to reduce moisture penetration. [2] Joints caught at the hairline-crack stage need less removal than joints left until the mortar crumbles, and less removal is less exposure to whatever tool is doing the removing.

One last thing belongs here for completeness, because cutting the joint correctly is only half of a repointing job. BIA states that the compressive strength of the repointing mortar must be equal to or lower than that of the original, that using a stronger mortar may significantly impair the surrounding brickwork, and that stronger repointing mortar increases stress concentration at the brick and mortar interface and can lead to spalling of the brick face. [2] A perfectly hand-cut joint filled with the wrong mix is still a failed repair. That is a topic of its own, and it is the next one we will cover.

Grinding and hand-cutting questions Chicago homeowners ask

Is grinding mortar joints bad for brick?

Not categorically, but the conditions attached to it are narrow. NPS permits thin diamond-bladed grinders under certain circumstances, on horizontal joints only, on hard portland cement mortar, operated by a skilled mason. [1] Outside those bounds NPS says the use of power tools by unskilled masons can be disastrous for historic masonry, particularly soft brick, and that on thin joints like most brick walls power saws almost always damage the units by breaking the edges and overcutting the vertical joints. [1]

Can a grinder be used on head joints?

No, and both sources say so for different reasons. NPS says mechanical tools should never be used on vertical joints because of the danger of slipping and cutting into the brick above or below. [1] BIA says a grinder will not remove the full depth of head joint material without damaging adjacent brick, and that the extra mortar left in head joints must be removed by chisel to achieve uniform depth. [2] Even where a grinder is permitted on bed joints, a chisel still has to do the head joints.

How deep should mortar be removed for tuckpointing?

NPS specifies a minimum of 2 to 2 and a half times the joint width, approximately half an inch to one inch for most brick joints, to ensure adequate bond and prevent mortar popouts. [1] BIA specifies a minimum of twice the joint width, generally three quarters of an inch, or until sound mortar is reached. [2] Both are minimums. NPS adds that any loose or disintegrated mortar beyond that depth should also be removed. [1]

Does using a power tool always mean damage?

No. NPS explicitly endorses one powered tool, saying small pneumatically-powered chisels generally can be used safely and effectively as long as masons maintain appropriate control over the equipment. [1] It also allows diamond-bladed caulking cutters, noting that they are slow and that they do not rotate but vibrate at very high speeds, thus minimising the possibility of damage to masonry units. [1] The concern in both briefs is the rotating abrasive wheel, not power as such.

Should the grinder do the whole bed joint?

No. NPS says automatic tools most successfully remove old mortar without damaging the units when used in combination with hand tools, and that where a power masonry saw is used to assist by cutting along the middle of the joint, final mortar removal from the sides of the joints still should be done with a hand chisel and hammer. [1] BIA reinforces the reason: thin slivers of mortar left on the brick must be removed to obtain good bond. [2]

How can I tell after the fact whether my joints were ground badly?

Look along the joint line at the edges of the bricks rather than at the mortar. NPS describes the damage signature as broken edges on the units and overcutting at the head joints. [1] Preservation Brief 1 adds that abraded masonry is left with a rough surface which tends to hold dirt and makes future cleaning more difficult. [3] Cut depth itself cannot be inspected once joints are filled, which is why NPS puts the tool decision on a test panel before the work rather than after it. [1]

How do I know whether my joints need repointing yet?

BIA lists the triggers: mortar erosion exceeding a quarter of an inch, crumbling mortar, mortar with voids, hairline cracks in the mortar, and cracks between the brick and mortar. [2] The check is visual observation plus light scraping with a metal tool, and BIA recommends seasonal inspections with binoculars for upper floors. [2]

Stats box

Definition bank

Entity cards

Diamond-bladed grinder

Hammer and masonry chisel

NPS Preservation Brief 2

BIA Technical Note 46

Abrasive surface damage

Ask which joints the wheel is going into

In short: One question separates a crew working to the standard from a crew working to the clock: who takes the head joints to full depth, and with what.

Almost everything in both documents converges on a single practical distinction. Bed joints can sometimes be cut with a thin diamond blade under conditions, and the sides still get finished by hand. [1] Head joints cannot be cut with a wheel at all, and NPS says never while BIA says the tool physically cannot reach depth without taking brick with it. [1] [2] A crew that grinds everything is not using a faster method. It is skipping the half of the method that protects the units.

The standards also tell you when to settle this, and it is before anyone is on scaffolding. NPS puts the decision on a test panel cut somewhere inconspicuous on your own wall. [1] BIA puts the skills assessment prior to the selection of the contractor, and warns that being an excellent mason is not the same qualification as being a repointer. [2] Both are asking you to make the tool question part of the bid rather than a discovery you make afterward, when cut depth has already disappeared behind fresh mortar.

If you are getting tuckpointing quotes on a Chicago building and want the tool method written into the proposal rather than left to the crew on the day, get a free quote and we will put in writing which joints get a blade, which get a chisel, and to what depth.

Sources

1. National Park Service, Preservation Brief 2, “Repointing Mortar Joints in Historic Masonry Buildings”, Mack and Speweik, rev. 1998. https://www.nps.gov/orgs/1739/upload/preservation-brief-02-repointing.pdf
2. Brick Industry Association, Technical Note 46, “Maintenance of Brick Masonry”, December 2017. https://www.gobrick.com/media/file/46-maintenance-of-brick-masonry.pdf
3. National Park Service, Preservation Brief 1, “Assessing Cleaning and Water-Repellent Treatments for Historic Masonry Buildings”, Mack and Grimmer, 2000. https://www.nps.gov/orgs/1739/upload/preservation-brief-01-cleaning-masonry.pdf