Types of Damage Caused by Incorrect Mortar in Brick Pointing

In this week’s blog article, we look at why improper brick pointing doesn’t actually save money. Scam pointing for example is very cheap. But it damages the brickwork and masonry and actually costs more money in the long term.  Proper tuckpointing, by comparison, is a more tedious but essential process to preserve masonry architecture and historic brick facades.

old-articleClick the adjacent image to take a look at last week’s blog article about visual examples of improper brick pointing. In this article, you can see several photographs from the field of actual brick walls which were pointed improperly. This week we talk about those issues and the resultant damage.

Scam pointing is also sometimes called strap pointing, in certain circumstances.   Improper tuck pointing, in general, is insidious, and the name strip pointing doesn’t sound quite as dangerous and bad as scam pointing. Nonetheless, both things are really similar and very destructive.   Scam pointing, unlike other types of improper pointing, is the application of a thin layer of mortar on top of a brick joint surface without prior raking of the joint or removal of the outer deteriorated mortar.

In last week’s article, we talked about visually apparent signs that indicate improper pointing has taken place.   In this article, today, we talk more about the long term negative effects of improper pointing. We look at what happens overtime to the building after pointing has been completed improperly. Tuck pointing, when done improperly, with the incorrect mortar or without proper joint raking or proper substrate hydration, causes significant long term damage to the building.

By using improper mortar, in historic masonry, the common type of mortar sold on the shelf at big box stores such as Home Depot and Lowe’s, for pointing and brick restoration, historic bricks will fail.  Historic bricks are comparatively softer and weaker,   Historic brick kilns used lower temperature fuel sources and therefore do not reach the high strength created from modern kilns today.  This mistake is easy to prevent, however the vast majority of contractors or construction workers in the historic neighborhoods of Washington DC and surrounding areas are untrained and unknowledgeable about the proper methodologies for historic masonry restoration.  Understanding the key characteristics such as compressive strength and moisture retention capacities requires knowledge and experience. Most of the masons in this area lack that knowledge.

Brick mortar, includes several different types of subcomponent materials but by-and-large all of those individual subcomponent materials can be broken down into 2 main classifications:

Brick mortar, includes several different types of subcomponent materials but by-and-large all of those individual subcomponent materials can be broken down into 2 main classifications:

  1. Sand or aggregate.
  2. A binder such as Portland cement or lime.

Using hard mortars, such as the Portland based mortars sold at the big box stores, causes pressure points in the masonry walls.  Bricks are generally heavy and hard, but they are not hard enough to withstand the pressure points caused by improper mortar at the outer edge of the joints. Using improper mortar or pointing improperly will cause brick spalling. Spalling may happen overtime and can actually take years to occur but can cause extremely expensive damage.   Surprisingly, the DC adopted Building Code does little to set guidelines for proper pointing.   It is largely incumbent upon building owners themselves to qualify and find Contractors who will tuckpoint historic masonry properly. There’s near nothing in code or regulation to protect them from all the other contractors who do work improperly.

The picture below shows an example of a brick with a spalled face.  The original clay brick face has cracked and fallen away from the masonry wall.  The only real way to fix this type of damage properly is to remove the brick and its entirely and install a new brick. Such work is costly, but the bigger problem is that the damage is more extensive than this one single brick.  Other bricks which have not yet cracked also have damage or pressure being applied to them which will cause damage in the future. The mortar used to point this wall is an improper type of mortar, a Portland mortar which is too hard for the strength of the brick.

brick-with-a-spalled-face

Even without knowing  more about the wall itself, you can identify a lot of information just from the photograph above. There is bio-colonization, the green growth shown on the surface of the wall. That indicates that the wall might be in a shaded area where it does not receive a lot of direct sunlight and therefore has slow dry-out. After heavy rains, this wall will take more time to dry out than the average wall because it doesn’t have direct exposure to typical ventilation, wind, or direct sunshine. These types of conditions are exacerbated or made worse from improper repointing. As moisture builds up in the joints of the walls, the mortar should breathe. A proper historic brick mortar is breathable, even more so than the brick itself. However, in a condition like this where a Portland mortar is used for tuckpointing instead of a proper historic mortar, that moisture becomes trapped and then builds up and leads to acute saturation of the brick which leads to freeze-thaw expansion in the Winter. Those conditions cause spalling and destruction of bricks.

freeze-thaw-expansion-brick

The picture above shows signs of overhydration and efflorescence in the brick wall.   Particular area of brick is lower in the wall and is possibly also impacted by rising damp, then the issue of rising damp is exacerbated by improper pointing.

This week, we had the opportunity to talk to John Speweik, a founding member of Speweik Preservation Consultants, Inc. in Elgin, Illinois.  Speweik is a renowned and accomplished expert in the field of proper historic masonry pointing and restoration and he explains that proper preservation should be taken seriously.  “Repointing mortar should be considered sacrificial, meaning that the mortar should intentionally be the part of a brick masonry assembly which is selectively weaker than the brick.  Not only should the mortar be intentionally weaker than historic brick, it should also have a greater permeability and breathability.”

A picture of John Spiewiek follows below, used with permission.

john-spiewiekSpalling is similar to delamination at stratification layers  common in sedimentary rock.  Sedimentary stone is formed by deposits laid over thousands of years, essentially like sheets that follow a grain.  (You can learn more about sandstone and brownstones at these links.)  The grain and individual layers in sedimentary rock are a type of stratification and variation in the internal parts of the stone.  Bricks also have a gradient, a differential and continuum of characteristics which change from the outer face to the inner center of the brick.  In historic kiln firing, for example, bricks reached different temperatures at different parts of the kilns.  Modern kiln firing uses higher temperature combustion fuels. However, in historic times with beehive kilns and in Washington DC, bricks were not fired at continuously even temperatures throughout. The outer parts of the brick will achieve a higher temperature and become more vitreous.

Speweik talked about the uneven or inconsistent firing processes of historic bricks.  “The historic bricks were stacked, by hand, in the historic kilns and once fired were removed and sorted by their position in the kiln. For example, bricks around the perimeter of the kiln would reach a higher temperature and therefore be separated and staged aside. Then, later in construction, those bricks fired at a higher temperature were more vitreous and would perform better at the exterior part of a partition.  The bricks fired at the center of the kiln would perform differently in terms of permeability and structural capacity and therefore be used on the inner parts of the exterior partitions.”  The lower temperature fired bricks still had the structural capacity to be part of a load bearing structural wall, but they would not perform as well to stand up to the elements of weather and nature.  Speweik also described the differences between the triple wythe wall and the double wythe above-grade walls common in Washington DC,  and historic masonry’s natural breathability which allows for self balancing of moisture retention and dissipation of moisture.

poor-repointing-2

The image below shows a lineup of 3 different examples of poor repointing.   In this case, you can see the pointing errors from far away.   In this case, the brick happens to be a bit more modern than traditional historic brick. This brick is called a tapestry brick. Tapestry bricks were fired at a slightly higher temperature than traditional historic bricks.  The Portland mortar used in this case, is not as damaging to a tapestry brick as it would be to a historic brick.

Since the tuckpointing and new mortar was applied in such a sloppy unprofessional way, it looks very bad. That issue alone is mostly aesthetic. Nonetheless, the aesthetic damage is significant and detracts from the value of the otherwise beautiful historic facade.

poor-repointing

The picture below shows the same wall, as the 3 instances shown in the image above, but this picture shows that wall from a greater distance. Even from across the street the naked eye can easily point out and identify the areas of improper tuck pointing. The aesthetic is so bad, that it’s obvious from a distance of over 75′ away.   The building has several beautiful architectural features such as stone quoining, a simple but visually pleasing running bond (similar to but weaker than the more prolific common bond), stone frieze; all well executed architectural elements, the value of which have been completely disregarded in the poor workmanship of the pointing work.

improper-tuck-pointing

This type of poor work is very disappointing, even if you just consider the aesthetic damage.   It’s disappointing because it’s so easy and inexpensive to avoid but so expensive to repair.  In the case of a tapestry brick, the work required to remove Portland mortar from the texture of the brick face is extremely tedious. In most cases, most methods of removal would require damage to the clay face of the brick.  The only methods of removal which would not damage the face of the brick would be extremely tedious and therefore very expensive.

proper-brick-tuck-pointing-exampleBy comparison, the picture below shows an example of proper brick tuck pointing. This work was done by our own company. We present the overall issue as an informative topic so that the building stakeholders of Washington DC who value and care about historic buildings can learn and understand the issues associated with improper tuckpointing. Infinity Design Solutions (IDS) is one of the few and rare companies, serving the Washington DC area, who care about the historic fabric of our city.

The building wall shown in the photo below is a historic common brick in Northwest Washington DC. The lime mortar used is a low PSI, high permeability mortar, intended to serve as a sacrificial buffer, protecting the historic bricks.

20220720_090236

Speweik discussed the general misunderstanding of historic brick masonry in today’s contemporary construction industry,

In 1997, in the Old House Journal, John Speweik wrote Old mortar, made from lime, sand, and water, is softer than historic brick. But modern portland cement mortar can be many times harder. The problem is, if portland cement is used for historic masonry, the bricks become the weakest part of the system. When the wall flexes with climatic change, the bricks absorb the force. This stress can crack, chip, and delaminate the brick. Plus, portland cement mortars do not breathe like lime mortars. Moisture may get trapped in the wall or may be forced into the masonry units.

Here in Washington DC, historic masonry buildings are extremely expensive and the amount of financial loss caused by improper repointing is staggering.   However, in addition to the direct financial value of the property, there is also a cultural loss when historic buildings are damaged. By comparison, consider neighboring poor cities, when historic buildings are damaged, it’s not just the loss of value to the property owner, there’s also a loss to all inhabitants and visitors of a city, present and future, who care about architecture, history, and culture.

We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the historic built environment of Washington DC and neighborhoods such as Capitol Hill, Dupont Circle, and Georgetown and become educated on on the difference between proper historic preservation versus improper work which leads to significant damage to the historic fabric of a building.

From a conservation and preservation perspective, several approaches can be taken to improve conditions related to deteriorated historic brick masonry. Primarily, lime mortar brick joints and low

temperature fired soft red clay bricks should be inspected and checked on a routine maintenance schedule, either seasonally or at least annually.   If brick masonry is kept in good condition, the life of embedded wood elements can be significantly extended.  Hire a professional contractor which specializes, understands and appreciates historic construction elements and buildings.

In this article we talked about the following terminology and  concepts, follow the links below for more related information from the IDS website:

These concepts are part of the fundamentals of historic masonry restoration, tuckpointing, and brick repair.

The links in the list above will take you to other articles with more information on defects, failures, preservation and repair of historic masonry.  You can learn a lot more on our blog.  Feel free to check it out.  If you have questions about the historic masonry of your building in Washington DC, fill out the webform below and drop us a line.  We will be in touch if we can help.