The Best Time of Year to Tuckpoint in Chicago: What the Temperature Rules Actually Say

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

Direct answer

In Chicago the tuckpointing season runs roughly from April through October, and the reason is temperature rather than tradition. The National Park Service sets the working window for repointing at wall temperatures between 40 and 95 degrees F, because that range prevents both freezing and excessive evaporation of the water in the mortar. [1] The Brick Industry Association explains why the bottom of that range is where it is: complete hydration of the cement only happens when material temperatures are 40 degrees F or higher, and below that the reaction slows and can stop, leaving soft, friable mortar with reduced durability. [2] Laid against NOAA’s 1991-2020 normals for Chicago O’Hare, April is the first month whose normal daily minimum sits at or above 40 degrees F, at 40.3, and October is the last, at 45.4. [5] Work outside that window is not impossible, but it is governed work: the TMS Specification requires heated materials, heated surfaces, enclosures and protection periods that get progressively more demanding as the temperature drops. [2]

TL;DR

• The governing number is a wall temperature, not a date. NPS puts it at 40 to 95 degrees F (8 to 38 degrees C), the range that prevents freezing or excessive evaporation of the water in the mortar. [1]
• BIA and the TMS Specification treat 100 degrees F down to 40 degrees F as normal weather requiring normal procedures. Below 40 degrees F, cold weather provisions start. [2]
• Cold weather is a curing problem, not a comfort problem. Cement hydration only completes at material temperatures of 40 degrees F or higher. [2]
• By NOAA’s 1991-2020 normals for O’Hare, the months whose normal daily low is at or above 40 degrees F are April through October. November’s normal mean is 41.3 degrees F but its normal low is 34.1. [5]
• Antifreeze in the mortar is not the workaround. NPS does not recommend it, and BIA says most commercial mortar antifreeze admixtures are actually accelerators, and at effective dosages usually cause a significant reduction in compressive and bond strength. [1] [2]
• Summer has its own failure mode. Rapid evaporation starves the cement of water, reducing strength development and bond, and NPS directs that repointing ideally be done in shade, away from strong sunlight. [1] [2]
• The job is not over when the crew leaves. NPS calls for burlap cover for the first three days and says mortar is usually fully hardened after about thirty days, depending on weather and exposure. [1]
• Inspect on a different schedule than you repair. BIA asks for periodic inspections, preferably each season, and NPS Brief 47 puts the annual walls inspection in spring. [3] [4]

One liner: Book the inspection in spring, book the work between April and October, and treat a December quote that promises no heat and no enclosure as a quote to walk away from.

What does “best time of year” actually mean for tuckpointing?

In short: It means the span of the year when the wall itself sits between 40 and 95 degrees F, because that is the range in which pointing mortar can cure properly.

Most seasonal advice about masonry is really advice about crew scheduling. The technical literature is not. The National Park Service treats scheduling as a material question and puts it first: in scheduling, seasonal aspects need to be considered first, and generally speaking, wall temperatures between 40 and 95 degrees F (8 and 38 degrees C) will prevent freezing or excessive evaporation of the water in the mortar. [1]

Read that sentence closely, because two details in it do most of the work. The first is that it is a wall temperature, not an air temperature. A south-facing Chicago wall in direct October sun is warmer than the air around it, and a north-facing wall in shade on the same afternoon is cooler. The second is the reason given for the range: it is about the water in the mortar. Below the bottom of the range, that water can freeze. Above the top of it, that water leaves too fast. Both ends are failures of the same thing, which is keeping enough water in the joint long enough for the cement to hydrate and the lime to carbonate.

The Brick Industry Association arrives at the same boundary from the construction side. Its Technical Note on hot and cold weather construction reproduces the TMS Specification’s requirements, and the band it labels normal weather, requiring nothing but normal procedures, runs from 100 degrees F down to 40 degrees F (37.8 degrees C to 4.4 degrees C). [2] Above and below that band, the specification stops being advisory and starts prescribing what the contractor must do to the materials, the wall and the finished work.

So the honest version of “when should I tuckpoint” is: whenever the wall will stay in that band through placement and through the curing days that follow. In Chicago that turns out to be a fairly generous stretch of the year, but it has hard edges, and the edges are where most of the avoidable damage happens.

Which Chicago months actually sit inside the working window?

In short: On NOAA’s 1991-2020 normals for O’Hare, April through October are the months whose normal daily low is at or above 40 degrees F.

The temperature rule is national. Applying it to Chicago requires Chicago numbers, so here are the 1991-2020 monthly climate normals for Chicago O’Hare International Airport, station USW00094846, as published by NOAA’s National Centers for Environmental Information. [5]

Two readings of that table matter, and they give slightly different answers. If you use the normal daily minimum, which is the conservative reading because it is the overnight number the fresh mortar has to survive, the months at or above 40 degrees F are April (40.3) through October (45.4). [5] If you use the normal mean daily temperature, which is the figure the TMS Specification ties its protection requirements to, November joins the list at 41.3 degrees F. [2] [5]

That difference is not academic. November’s normal mean of 41.3 degrees F is barely above the 40 degrees F trigger, and its normal low of 34.1 degrees F is below freezing-adjacent territory on an ordinary night. A November job is a job where the protection requirements are likely to come into force partway through, which means it needs to be priced and planned that way rather than discovered that way.

At the warm end, Chicago barely tests the ceiling on paper. The warmest normal daily maximum in the table is 84.5 degrees F in July, comfortably under the 95 degrees F NPS limit. [5] But the NPS limit is a wall temperature and these are air temperatures, and normals are thirty-year averages rather than the day your crew is on the scaffold. A sunlit brick face on a 90 degree July afternoon is well past 95 degrees F, which is exactly why NPS directs that repointing ideally be done in shade, away from strong sunlight, in order to slow the drying process, especially during hot weather. [1]

The practical summary: April through October is the season, with the two ends of it deserving more care than the middle, and July and August deserving shade and water discipline rather than avoidance.

Why does cold weather damage fresh pointing mortar?

In short: Because cement hydration only completes at material temperatures of 40 degrees F or higher, and water freezing inside a wet joint expands and breaks it.

BIA is unusually direct about the mechanism. The primary purpose of the cold weather construction procedures, it says, is to achieve complete hydration of the cement, which occurs only when material temperatures are 40 degrees F (4.4 degrees C) or higher. Some heat is generated by the reaction itself, which can keep the material above that threshold when ambient temperatures are slightly lower, but as ambient temperatures fall the chemical reaction slows and may stop completely unless adequate heat is maintained. Incomplete cement hydration can result in soft, friable mortar with reduced durability. [2]

Soft, friable mortar with reduced durability is the whole problem in one phrase. It is not a cosmetic outcome. It is a joint that looks finished, passes a glance from the sidewalk, and then erodes out over a handful of winters, putting you back where you started with the money already spent.

There is a second, faster failure alongside it. Mortar mixed during cold weather often has lower water content, increased air content and reduced early strength compared with mortar mixed at normal temperatures, and BIA lists the consequences as reduced compressive strength, bond strength and extent of bond, as well as reduced water penetration resistance. [2] That last one matters most for tuckpointing specifically, because reducing water penetration is the entire reason the work is being done. BIA’s own maintenance guidance frames repointing as one of the most effective ways to reduce moisture penetration. [3] Cold-weather pointing that comes out less water-resistant than it should be has undermined its own purpose.

Then there is freezing itself. BIA gives a specific threshold: mortar with a water content greater than 6 percent, which it calls the wet condition, will likely be damaged by the volumetric expansion of the water during freezing. [2] A freshly packed joint is a wet joint. That is why the specification does not merely ask for warm mortar at the moment of placement but requires the finished work to be protected for a period afterwards.

Can you tuckpoint in a Chicago winter at all?

In short: Yes, but under prescribed cold weather provisions that escalate in four steps as the temperature falls, and they cost money.

Cold weather masonry is a defined practice, not a prohibition. BIA reproduces the TMS Specification’s requirements as a four-tier table, and the tiers tighten as it gets colder. [2] Here is what each tier adds.

Below 40 degrees F down to 32 degrees F, the crew may not lay units that are below 20 degrees F or that carry frozen moisture, visible ice or snow on their surface. Visible ice and snow must be removed from existing foundations and masonry that will receive new work, and those surfaces heated above freezing by methods that do not damage them. Mixing water or sand must be heated to produce mortar between 40 and 120 degrees F, and neither water nor aggregates may be heated above 140 degrees F. The completed work must be covered with a weather-resistive membrane for 24 hours. [2]

Below 32 degrees F down to 25 degrees F, everything above still applies and mortar temperature must be maintained above freezing until it is used in the masonry. [2]

Below 25 degrees F down to 20 degrees F, masonry surfaces must be heated on both sides to 40 degrees F, windbreaks or enclosures are required when wind velocity exceeds 15 mph, and newly constructed masonry must be covered completely with weather-resistive insulating blankets or equal protection for 24 hours after completion. [2]

Below 20 degrees F, the crew must provide an enclosure and auxiliary heat to hold the air temperature above 32 degrees F inside it, and the new masonry must be kept above 32 degrees F for at least 24 hours afterwards. [2]

One detail in that table is easy to skim past and worth stating plainly, because it changes how a winter quote should be read. BIA notes that preparation and construction requirements are based on ambient temperatures, the outdoor temperature at the time considered, while protection requirements are based on mean daily temperatures, which are calculated by adding the maximum and minimum temperature for a 24-hour day and dividing by two. [2] A crisp, sunny 45-degree afternoon in late November can carry a mean daily temperature under 40 degrees F once the overnight low is averaged in. The work may proceed under normal procedures while the protection requirements are already triggered.

There is also a flat prohibition worth knowing. If snow or ice is visible on existing foundations or masonry, the TMS Specification prohibits building new masonry on them, because there is danger of movement when the base thaws and bond cannot be developed between the mortar bed and frozen supporting surfaces. [2] A crew that scrapes a joint clear and points into a wall that still has ice in it is not cutting a corner on comfort. It is building a bond that will not form.

None of this is free. Heated water and sand, enclosures, insulating blankets and auxiliary heat are labour and equipment that a May job does not need, which is the practical reason winter tuckpointing is both more expensive and more dependent on the contractor doing things you cannot see from the ground. If you are weighing that trade-off, our breakdown of what tuckpointing costs in Chicago covers where the money goes on an ordinary job.

Why is antifreeze in the mortar the wrong answer?

In short: Because most mortar antifreeze admixtures are accelerators rather than antifreezes, and at effective dosages they significantly reduce compressive and bond strength.

This is the single most common shortcut offered when a homeowner asks about cold weather work, and both primary sources reject it independently.

BIA’s instruction is a flat one: do not use antifreeze compounds. These admixtures are made with alcohols or combinations of salts intended to reduce the freezing point of a substance, but most commercial mortar antifreeze admixtures do not lower the freezing point of mortar or grout and are actually accelerators. If antifreeze compounds are used in the quantities required to be effective, BIA says the result is usually a significant reduction in mortar compressive strength and bond strength. [2]

NPS reaches the same conclusion by a different route, aimed at older buildings. The use of antifreeze compounds is not recommended; they are not very effective with high lime mortars and may introduce salts, which may cause efflorescence later. NPS then gives the alternative in one line: a better practice is to warm the sand and water, and to protect the completed work from freezing. [1] That is precisely what the TMS tiers require, which is a useful sign that the two documents are describing one consensus rather than two opinions.

Accelerators proper are a narrower question. NPS notes that accelerators are used to reduce mortar freezing prior to setting, and that selection of admixtures should be made by the architect or architectural conservator as part of the specifications, not something routinely added by the masons. [1] BIA is similarly cautious: calcium chloride, while effective and used in the past, is not recommended because it corrodes metals used in masonry such as ties, anchors and reinforcement, and admixtures with more than 0.2 percent chloride ions are prohibited for use in mortar under the TMS Code. Non-chloride compounds such as calcium nitrite and calcium nitrate are the recommended alternative where an accelerator is approved. [2]

And the decisive point for anyone being sold a winter job on the strength of an additive: BIA says the use of accelerators alone is not recommended, because they do not address all concerns related to cold weather construction, and masonry constructed using accelerators in mortar or grout must still be protected from freezing. [2] The additive never replaces the heat and the cover. If a quote offers it as a substitute for them, the quote is wrong on the specification.

What goes wrong in a Chicago July?

In short: Water leaves the joint faster than the cement can use it, which costs strength and bond, so hot-weather work is about shade, timing and wetting.

Summer failures are quieter than winter failures, which is part of why they are more common. Nothing visibly goes wrong on the day.

BIA describes the mechanism as rapid evaporation and absorption of water from the mortar. Rapid water loss due to evaporation reduces the amount of water available for hydration and reduces the strength development of the mortar; without sufficient water, cement hydration slows or stops, which reduces the bond strength and extent of bond between brick and mortar. The integrity of the masonry may also be compromised by mortar that flash sets before completing hydration. [2] Notice that the end state is the same as the cold weather end state: incomplete hydration, weak bond. Only the route there differs.

NPS adds the lime-mortar version of the same warning, which is the relevant one for Chicago’s older building stock. Preliminary hardening of high-lime mortars takes place fairly rapidly as water in the mix is lost to the porous surface of the masonry and through evaporation, and a high lime mortar left to dry out too rapidly can result in chalking, poor adhesion, and poor durability. [1]

The countermeasures are ordinary and checkable. NPS says repointing should ideally be done in shade, away from strong sunlight, and that for large-scale projects shade can be provided with appropriate modifications to scaffolding. [1] It also handles the substrate: at the time of filling, joints should be damp but with no standing water present, and for extremely absorbent masonry such as limestone, sandstone and common brick, a continual mist of water should be applied for a few hours before repointing begins. [1] BIA’s version is the same instruction from the other side: the joints should be dampened, but to ensure a good bond the brickwork must absorb all surface water before the repointing mortar is placed. [3]

Mix discipline tightens in heat too. NPS notes the total volume of water needed may vary from batch to batch depending on weather conditions, that mortar should be used within approximately 30 minutes of final mixing, and that retempering, meaning adding more water later, should not be permitted. [1] On a 90-degree afternoon those are not formalities.

One reassurance from the Chicago numbers: the TMS hot weather provisions proper, which start above 100 degrees F or 90 degrees F with a wind velocity greater than 8 mph, are not routine here. [2] O’Hare’s warmest normal daily maximum is 84.5 degrees F. [5] Chicago summer tuckpointing is a workmanship question rather than a code-provision question, which means it depends almost entirely on whether the crew bothers.

Is spring or fall the better half of the season?

In short: Both sit comfortably inside the window; spring has the advantage that the inspection literature points there, and that the repair gets a full season to cure before winter.

Once you are inside April to October, the temperature rule stops discriminating. May’s normal mean of 60.6 degrees F and September’s of 66.3 degrees F are both squarely in range, and neither month’s normal extremes come near either boundary. [5] So the choice gets decided by things other than the thermometer.

The inspection literature leans spring. NPS Preservation Brief 47 publishes an inspection frequency chart for building exteriors and places exterior walls and porches at annually, in spring. [4] Chimneys are the exception in that chart, placed in fall, prior to the heating season, with a mason’s inspection every five years. [4] Foundations and grade are listed as spring or during the wet season. [4] If you inspect in spring and the inspection finds deteriorated joints, booking the work for late spring or summer follows naturally, and the repair has months of above-40 weather ahead of it rather than weeks.

That last point is the practical argument for the front half of the season, and it rests on how long mortar actually takes to finish. NPS says new mortar joints are especially susceptible to damage because they do not become fully cured for several months, and that thirty days is usually sufficient for the mortar to be fully hardened, depending on weather and exposure. [1] Work finished in early October in Chicago has its thirty-day hardening period running into November, whose normal daily low is 34.1 degrees F. [5] Work finished in June does not have that conversation at all.

Fall has a real advantage of its own, which is that the wall has just been through a full wet season and is showing you its worst. NPS Brief 47 says it is best to inspect walls during dry as well as wet weather, looking for moisture patterns that appear after heavy or sustained rainfall or snow. [4] A crack that only reveals itself as a damp patch after three days of rain is invisible on a dry afternoon in May.

The defensible answer is therefore a sequence rather than a single month: inspect in spring as Brief 47 suggests, confirm what you found after the next sustained rain, and schedule the work with enough of the warm season left that the mortar gets its thirty days and then some. [1] [4]

What has to happen after the crew leaves?

In short: Curing is protected work: damp joints, burlap for three days, misting as needed, and roughly thirty days before the mortar is fully hardened.

A tuckpointing job is not finished when the last joint is tooled, and the aftercare is temperature-dependent in both directions. This is the part of the specification most likely to be silently dropped, because nobody is watching by then.

NPS gives the routine. Once the joints are thumb-print hard and have been finish tooled, periodic wetting of the repointed area may significantly accelerate the carbonation process; where feasible, misting with a fine-nozzle hand sprayer can be done for a day or two after repointing. Local conditions dictate the frequency, but initially it may be as often as every hour, gradually reduced to every three or four hours. Walls should be covered with burlap for the first three days after repointing, and if plastic is used it should be tented out and not placed directly against the wall. [1]

In cold weather the protection is mandated rather than recommended, and it is keyed to the mean daily temperature. When the mean daily temperature falls to 40 degrees F or below, newly constructed masonry must be covered with a weather-resistive membrane for at least 24 hours after completion, and the covering should extend a minimum of 2 ft down each side of the wall. [2] BIA adds a genuinely useful piece of salvage guidance: if newly constructed masonry is frozen, it may be moistened after thawing to reactivate the hydration process and allow the masonry to continue developing strength. [2]

Two timelines are worth writing into your own calendar. BIA’s maintenance note says replaced masonry should be properly cured, which it puts at five to seven days, before intermediate sections or supports are removed. [3] NPS says mortar should be fully hardened before any cleaning, which is usually thirty days depending on weather and exposure, and that the mortar continues to cure even after it has hardened. [1] If a contractor proposes to acid-wash the elevation the week after pointing it, that is a specification problem, not a scheduling preference.

Cleaning has its own weather rule, and it is stricter than the pointing rule. BIA says masonry should not be cleaned during freezing weather or when freezing weather is expected, because many cleaning methods require the wall to be saturated with water, and it recommends that water-based cleaning methods be used only if the ambient temperature will be 40 degrees F or above and will remain so until the brickwork is dry. [2] In hot weather the opposite risk applies: the area must be thoroughly saturated before the cleaning solution goes on, water may need reapplying, and if cleaning solutions are allowed to dry on the brickwork, damage or staining of the masonry can result. [2]

When should you inspect, and when should you book?

In short: Inspect each season and formally each spring; book the work for the April to October window; do not let a seasonal rule delay a structural finding.

Inspection and repair run on different clocks, and conflating them is how people end up either over-servicing a sound wall or sitting on a moving one.

BIA’s maintenance guidance asks for periodic inspections, preferably each season, and explains why: seasonal inspection periods are recommended so that the behavior of building materials in various weather conditions can be observed. [3] It also tells you how to see the parts you cannot reach, suggesting binoculars and the use of adjacent roof areas and balconies for close-range observation of conditions at upper floors. [3] NPS Brief 47 adds the trigger that no calendar covers: all building features should be inspected after any significant weather event such as a severe rainstorm or unusually high winds. [4]

What you are looking for, when the question is whether joints need pointing, is specified. BIA lists the conditions that call for repointing as mortar erosion exceeding a quarter inch (6.4 mm), crumbling mortar, mortar with voids, hairline cracks in the mortar, and cracks between the brick and mortar. [3] If none of those are present, the seasonal question is moot. For the difference between what tuckpointing addresses and what full repointing means, our post on tuckpointing versus repointing covers the terminology.

There is one category where the seasonal window should not govern your timing at all. BIA keeps a separate list of conditions that are structural rather than maintenance, outside the scope of its maintenance guidance and warranting investigation by a professional engineer: cracks exceeding 0.075 in. (2 mm) in width, cracks through multiple brick units, cracks following a stepped or diagonal pattern, widespread spalled brick, accumulated rust on lintels or shelf angles, out-of-plane movement, and neutral or negative slope on masonry sills and water tables. [3] If your spring inspection turns up one of those, the answer to “when should we do this” is not “May”. It is “get an engineer to look at it now”.

Equally, NPS is clear that a seasonal window does not fix a drainage problem. The root cause of deterioration, whether leaking roofs or gutters, differential settlement, capillary action causing rising damp, or extreme weather exposure, should always be dealt with prior to beginning work; without appropriate repairs to eliminate the source, mortar deterioration will continue and any repointing will have been a waste of time and money. [1] Perfectly timed tuckpointing under a broken downspout is still wasted tuckpointing.

Finally, a note on who does it, because the season does not compensate for the crew. BIA says repointing operations should be performed only by qualified and experienced repointing craftspeople, that an individual who is an excellent mason may not be qualified for repointing, and that skills should be tested and evaluated prior to selecting the contractor. [3] That is a strong statement from a trade body, and it is the reason the temperature rules above are worth asking about directly. A crew that can answer them is a crew that has been taught them.

Tuckpointing season questions Chicago owners ask

What is the best month to tuckpoint in Chicago?

Any month from April through October satisfies the temperature rule. On NOAA’s 1991-2020 normals for O’Hare, those are the months whose normal daily minimum is at or above 40 degrees F, from 40.3 in April to 45.4 in October. [5] NPS sets the working window at wall temperatures of 40 to 95 degrees F. [1] Within that span, finishing earlier leaves more warm weather for curing, since NPS puts full hardening at about thirty days depending on weather and exposure. [1]

Can you tuckpoint in winter?

Yes, under the cold weather provisions of the TMS Specification, which escalate in four steps below 40 degrees F. They require heated mixing water or sand, mortar between 40 and 120 degrees F, heated masonry surfaces, windbreaks or enclosures above 15 mph wind, and covered or heated protection of the finished work for 24 hours or more. [2] It is legitimate work, but it costs more and depends on the contractor actually doing it.

What temperature is too cold to tuckpoint?

Below 40 degrees F, cold weather provisions apply rather than normal procedures. [2] Complete hydration of the cement occurs only at material temperatures of 40 degrees F or higher. [2] Masonry units below 20 degrees F, or carrying frozen moisture, visible ice or snow, must not be laid at all. [2]

Is it bad to tuckpoint in the rain?

The sources address dampness rather than rain directly, and they are specific about it. At the time of filling, joints should be damp but with no standing water present. [1] BIA says the joints should be dampened but the brickwork must absorb all surface water before the repointing mortar is placed, because surface water prevents good bond. [3]

Does antifreeze in mortar work?

No. BIA says most commercial mortar antifreeze admixtures do not lower the freezing point of mortar or grout and are actually accelerators, and at the quantities required to be effective the usual result is a significant reduction in compressive and bond strength. [2] NPS does not recommend them either, noting they are not very effective with high lime mortars and may introduce salts that cause efflorescence later. [1]

How hot is too hot for tuckpointing?

NPS puts the ceiling at a wall temperature of 95 degrees F. [1] The TMS hot weather provisions start above 100 degrees F, or 90 degrees F with a wind velocity greater than 8 mph. [2] Chicago rarely reaches those on normals, with a warmest normal daily maximum of 84.5 degrees F in July, [5] but a sunlit wall runs hotter than the air, which is why NPS directs repointing be done in shade away from strong sunlight. [1]

How long does tuckpointing take to cure?

NPS says mortar is usually fully hardened after about thirty days, depending on weather and exposure, and that new joints do not become fully cured for several months. [1] BIA puts the shorter figure for replaced masonry at five to seven days before intermediate sections or supports are removed. [3]

What should the crew do after they finish pointing?

NPS calls for covering the walls with burlap for the first three days after repointing, tenting any plastic out rather than placing it against the wall, and misting the repointed area once the joints are thumb-print hard and finish tooled, initially as often as every hour and reducing to every three or four hours. [1] In cold weather, a weather-resistive membrane for at least 24 hours is required once the mean daily temperature falls to 40 degrees F or below. [2]

When should I inspect my brickwork?

BIA recommends periodic inspections, preferably each season, so the behavior of the materials in different weather can be observed. [3] NPS Preservation Brief 47 puts the annual inspection of exterior walls in spring, and chimneys in fall prior to the heating season. [4] Both add that any significant weather event warrants an extra look. [4]

Does the season matter if my wall has a structural crack?

No, that changes the question. BIA lists cracks exceeding 0.075 in. (2 mm), cracks through multiple units, stepped or diagonal cracks, widespread spalled brick, accumulated rust on lintels or shelf angles, out-of-plane movement, and neutral or negative slope on sills as structural conditions warranting investigation by a professional engineer. [3] Those are assessed when found, not when the weather is convenient.

Stats box

Definition bank

Entity cards

Tuckpointing season in Chicago

Cold weather masonry provisions

Hot weather masonry provisions

Curing and aftercare

Getting the season right, and the questions that prove it

In short: Ask a prospective contractor what wall temperature they work down to and what they do to the finished joints for the first three days. The answers tell you everything.

The season is the easy part of this. April through October in Chicago satisfies the temperature rule with room to spare, and outside that window the TMS Specification tells a competent contractor exactly what to do instead. [2] [5] The harder part is that almost none of it is visible from the ground after the fact. A joint pointed at 35 degrees F without heat looks identical to a joint pointed at 60 degrees F, for about three winters.

So the useful questions are narrow ones. What wall temperature do you stop working at, and do you go by ambient or mean daily? [2] Do you prehydrate the pointing mortar, and how long before placement? [3] Do you dampen the joints and let the brickwork absorb the surface water before packing? [1] [3] What goes over the work for the first three days? [1] And if it is November, what is the protection plan when the mean daily temperature drops below 40? [2] A crew that has been trained on this literature answers those in a sentence each. A crew that has not will change the subject to price.

One last thing worth repeating, because it outranks every scheduling question on this page: if the inspection turns up cracking over 0.075 in., stepped or diagonal cracking, widespread spalling, rust on lintels, out-of-plane movement or sills sloping the wrong way, BIA puts those outside maintenance entirely and calls for a professional engineer. [3] That is not a spring job or a fall job. That is a now job.

If you want someone to look at your joints and tell you honestly whether this year’s window still has room in it, get a free quote, or read more about how we approach tuckpointing in Chicago.

Sources

1. National Park Service, Preservation Brief 2, “Repointing Mortar Joints in Historic Masonry Buildings”, Robert C. Mack, FAIA, and John P. Speweik, rev. 1998. https://www.nps.gov/orgs/1739/upload/preservation-brief-02-repointing.pdf
2. Brick Industry Association, Technical Note 1, “Hot and Cold Weather Construction”, June 2018. https://www.gobrick.com/media/file/1-tn1.pdf
3. Brick Industry Association, Technical Note 46, “Maintenance of Brick Masonry”, December 2017. https://www.gobrick.com/media/file/46-maintenance-of-brick-masonry.pdf
4. National Park Service, Preservation Brief 47, “Maintaining the Exteriors of Small and Medium Size Historic Buildings”, Sharon C. Park, FAIA, June 2007. https://www.nps.gov/orgs/1739/upload/preservation-brief-47-exteriors-small-medium-buildings.pdf
5. NOAA National Centers for Environmental Information, U.S. Monthly Climate Normals 1991-2020, Chicago O’Hare International Airport, station USW00094846. https://www.ncei.noaa.gov/access/services/data/v1?dataset=normals-monthly-1991-2020&stations=USW00094846&format=json&startDate=0001-01-01&endDate=9996-12-31&dataTypes=MLY-TAVG-NORMAL,MLY-TMIN-NORMAL,MLY-TMAX-NORMAL