Last summer as I presented a masonry restoration proposal to a building in Chicago, one of the property managers queried, “We haven’t needed any tuckpointing in 30 years, why do we have to do it now?” At first glance, it would seem that some questions do answer themselves, but what this person was really asking was what is tuckpointing and why do we need it done.

Brick and mortar have been utilized in construction for centuries; they have uncovered brick walls that date back 6000 years. They are aesthetically pleasing, extremely durable, and with proper maintenance can last almost indefinitely. The longevity of brick is generally considered in excess of 100 years, while a properly-installed mortar joint should last approximately 25 years. Age, weathering, materials used, and environmental conditions can all contribute to the deterioration of the mortar joints. The removal and replacement of these deteriorated joints is termed tuckpointing.

In tuckpointing, the joints to be replaced are ground out to a sound base, flushed with water or compressed air to remove the dust, and a new tuckpointing mortar is laid into the joints. In considering repointing of joints, it is important to determine which joints need to be replaced. A tuckpointed joint does not have the longevity (15 years) as an original sound mortar joint, so care should be taken to replace only those joints which are in need of repair. Typically joints that are eroded and have loose or crumbling mortar, or have cracks either in the mortar or between the bricks and the mortar, are candidates for replacement.

Technical aspects

Mortar is removed utilizing grinders and/or chisels. The depth of the removal should be equal to or exceed twice the mortar joint thickness in order to have depth to the repair, and is usually specified to a depth of three-quarter inch. This can be exceeded where necessary to reach sound mortar. The back of the joint should be flat and clear of mortar. Great care should be taken during the removal process so as to not damage the adjacent masonry units.

After the mortar has been removed, the joints are cleaned and prepared for the installation of new mortar.

To avoid damage to the existing brick, it is important to select a mortar that has a compressive strength similar to or weaker than the original mortar. A mortar with a higher compressive strength can actually cause the brick to deform and spall (spalling refers to when the face of the brick has fallen off exposing the softer interior of the brick to the elements).

The two bodies that determine the specifications of mortar are the BIA (Brick Institute of America) and the ASTM (American Society of Testing and Materials). They recognize five different Portland cement-hydrated mortars; all a combination of Portland cement, lime, sand, and water. These materials are mixed in different proportions and those proportions determine the strengths and properties of the mortar. Of the five mortar types in use today, M S N O and K (every other letter in the term “mason work” in case you’re ever on Jeopardy), type N is the most commonly used. It has a ratio of one part Portland cement, one part hydrated lime, and six parts sand. This gives it an excellent combination of medium compressive strength and workability — both crucial to a successful project.

It should be noted that there is a lime putty mortar used in historical restoration, but Portland cement has been in wide use since the late 1800s, so most buildings will have a Portland cement mortar.

After a mortar has been selected it is not just a matter of mixing it with water and placing it in the wall; the mortar needs to be pre-hydrated first. This is a process where it is mixed with water and allowed to sit for one hour in order for all the elements to hydrate (take in the water) before retempering with water for use. This greatly reduces the shrinkage in the mortar and provides for a more successful outcome.

The process of repointing can now take place. The replacement mortar should be applied in layers or lifts of a depth of one-quarter inch at a time; this layering and compaction insures bond with the adjacent masonry surfaces. Completed work should be wet down with water to retard the curing process. While care should be taken to place the mortar only into the joints, cleaning of excess mortar smears from the brick faces may be necessary. This should be accomplished with a phosphate type cleaner, not an acidic cleaner, as this burns and ages the mortar.

Aesthetic considerations

Aside from the physical properties of the mortar, consideration should also be given to the color of the mortar and the configuration of the finished joint. Through the use of metallic oxide pigments, most commonly red, black, and buff, in different proportions, it is possible to match the existing mortar quite closely. You really shouldn’t be able to see the repair from three blocks away.

There are many types of finished mortar joints; brushed, concave, roped, etc. The finished joint should match the adjacent joints as closely as possible in shape and appearance.

There are a number of buildings in our area where the mortar joints were placed without grinding out the existing mortar. This process of “buttering” the joints with a thin layer of mortar makes the joint appear much wider and greatly detracts from the appearance of the building. These thin layers can also hold moisture, undermine the masonry, and should be avoided.

Sometimes caulking is used in lieu of mortar. This is most often where areas of movement have occurred within the masonry wall. While this can be effective due to the flexibility of the material, it does need to be installed correctly. This entails grinding the mortar within the crack to a one-quarter inch depth and the installation of bond breaker tape prior to placing the sealant. While this can be useful, it must be remembered that caulking is not breathable like mortar and can trap moisture into the wall. I was called to a parochial school where all the mortar joints had been caulked over. They were extremely flexible but the trapped moisture was causing all the bricks to spall, necessitating the removal and replacement of all the exterior masonry.

Conclusion

As you can see, the tuckpointing process is a bit more involved than the nip/tuck as the title of this article suggests. You should proceed diligently and select a contractor that is familiar with all aspects of the restoration process. Just because a particular contractor is skilled at replacing your roof, painting your siding, or even laying brick doesn’t make them qualified to tuckpoint your building. Of course, being licensed and having proper insurance is important, and you should also ask to see a copy of their safety program (if they don’t care about their workers, why would they care about your building?) You can also ask them to do a “mock-up.” This is where they do an actual sample of the methodology and materials on your building so you can see a representation of what the final results will be. Some companies charge for this, but a small investment in money and time at the onset of a project will insure the finished result and the performance of your masonry structure.

To contact Dakota Evans Restoration, Inc., you may reach out to member representative Mike Landry at  
(847) 439-5367 or mike@dakotaevans.com.