Chicago Home Primer - Blog

We’ve all heard the term “tuckpointing”. It is the standard designation for every method of smearing cement mortar on bricks. But, almost no one knows what this word really means, and because of it………

We Are Destroying Our Masonry City

Chicago is a masonry city. Yes, there thousands of wood frame buildings throughout our city, but when one travels the neighborhoods, it becomes obvious very quickly that this is a city built with bricks and mortar. Competently constructed masonry buildings need very little repair or maintenance, but it sometimes becomes necessary to perform repairs. The problems come from how those repairs are made.

On its face, it seems relatively simple. Take out the old stuff and put in some new stuff, or smear some new stuff over the old stuff. The problems come from the “stuff”. Most folks don’t realize it, but the masonry materials we use in modern construction are completely different, (like, down to a molecular level different), than the materials our masonry homes were built with several decades ago.

The old original salmon colored Chicago Common brick was softer and and more absorbent than modern brick. It also expanded and contracted with atmospheric changes, so it was necessary to use a softer mortar that had similar expansion characteristics as the brick. The mortar that was used in the original construction was lime based, either lime mortar, or a mixture called lime putty.

Lime rich mortar has several characteristics that are completely different than modern additive laden mortars. As water migrates through lime mortar, molecules of lime travel with the water and refill small cracks that occur due to settlement (called autogenous healing). Lime mortar will expand & contract to account for movement caused by atmospheric changes. It also was compatible with the moisture permeability of the bricks so water was absorbed and evaporated equally from both materials. The older (solid) masonry would absorb some amount of moisture, but the sheer mass of the wall would limit the amounts of moisture & the depth of penetration, and the moisture will evaporate back out of the wall with atmospheric change.

Modern Portland cement mortars are hard, brittle, and moisture resistant. When new Portland cement mortars are laid over the old original lime mortar(s), the water resistant mortar retains water in the wall. When the walls freeze and thaw in winter, the retained water expands and the walls fracture and fall apart. Building owners see the deterioration occurring, and mistakenly think they need to add more and more Portland cement to “keep the water out”. What they are actually doing is keeping the water “in”. Subsequent repairs with modern mortars accelerate the deterioration of the wall, as each new application seals the wall tighter and tighter. The end result is substantially damaged masonry.

Many restoration masons utilize modern Portland cement mortars because they are readily available at the big box stores, they are fast to mix and apply, and most significantly, the masons don’t have a clear understanding of what is necessary to perform a proper long lasting repair in the first place. In the end, the less savvy building owner thinks that since the entire wall is clean looking and appears to have been “re-pointed” uniformly, he has received a good and very affordable repair. In fact, what they receive was a cosmetic overlay, which in most cases, accelerates the deterioration of the masonry.

The most common result of improper mortar application is that the thin layer of scrub mortar cracks & falls off within a few years. In the areas where the new mortar extends deep enough to remain in place, moisture tends to be trapped in both the mortar bed joints and the edge surfaces of the brick. This causes the moisture laden brick to deteriorate through the expansion that occurs as it freezes. This condition is called spalling. Entire faces of brick can literally begin to progressively fall away. In many cases, the trapped moisture will cause entire sections of brick to bulge out away from the building due to freeze/thaw cycles. In both cases, the result is substantially damaged masonry.

The other large problem with old masonry is the steel lintels over the windows and doors. Over the years, moisture migrates into the wall, where it attacks the steel and causes it to rust and delaminate. When the steel delaminates, it flakes and expands, very slowly, but w/thousands of pounds of force. The expanding steel causes the brick around the windows to bulge, and causes decorative stonework to crack. The most common (and mistaken) repair is to caulk and seal the lintels, which the repairman imagines is keeping water out of the wall. What is happening is water is being held/retained in the wall, and the lintels deteriorate faster.

Another common problem with the lintels is the relatively recent practice of wrapping the window trim and steel lintels with aluminum when windows are replaced. The intent is to protect the lintels, but the aluminum wrap holds water into the wall, which accelerates the deteriorioration of the lintel.

These misbegotten repair practices are so ingrained in Chicago culture, it has become standard practice to keep applying new mortars over the old mortars until there is a convex bulging mortar joint instead of a nicely struck flush joint. There are some new masons that have labeled this “European Tuckpointing”, as if the practice has some centuries old roots going back to the “olde” country. While the new masons understanding of American marketing is admirable, the practice is a disaster for some buildings because the bulging joint has thousands of little ledges and gaps that trap moisture and actually funnel increased amounts of moisture into the wall.

There are a couple simple lessons in all of this.

First, it is not necessary to “protect” the older mortars. If we don’t actively abuse our buildings by applying the wrong principles, materials, and methods, they will last. They have withstood thousands of years of use all over the world, and if the building is reasonably maintained, tuckpointing is most likely only necessary every 25-30 years at most. Yes, there might be miscellaneous spot repairs necessary, or the building owner might want to clean the masonry to make it look better, but plainly and simply, the original mortars will function just fine for decades if they are not slathered with Portland cements, or otherwise abused by not maintaining roofing or other waterproofing components of the building.

Second, if one is doing repairs to their masonry building, they should be aware that there are vast differences in the mortar, and using the wrong mortar is detrimental to the building. When talking to your repair mason, make sure they understand these things. If they don’t, the likelihood is they are going to damage your building, not repair it.

Which finally brings us to tuckpointing.

Tuckpointing was originally a nineteenth century old English decorative masonry jointing technique that uses two different color mortars to simulate the appearance of narrow mortar joints. The primary mortar joint is applied in a color similar to the bricks, then a second lighter shade mortar is “tucked” into a groove in the primary joint. Americans imported the technique, but the terminology was changed right here in Chicago in the mid-nineteenth century and the new meaning was eventually adopted throughout the Midwest as a masonry repair technique instead of it’s original decorative meaning. (Michael Shellenbarger, 1991, The Journal of the Association for Preservation Technology)

The correct term for this repair work is “repointing”, or simply “pointing”. What this means to us is even the terms that the new generation of masons not only use the wrong mortars, they don’t even use the proper terminology for their work. Call me old fashioned, but if someone doesn’t even know the correct terminology for the processes they employ, I tend to distrust their knowledge and skill for executing the work.

We are blessed with a very unique architecture and building material in this City we call home. If we want our masonry homes to continue on, we must educate ourselves, and then the tradesman that work on our properties. If we don’t do these things, we can expect that our homes will fall apart rapidly and have excessive repair costs. It’s always cheaper to do things right the first time.

If you are contemplating masonry repair, you want to know that your mason understands these very basic fundamentals.