A very disturbing new finding. Will these buildings fall apart?
By William Decker, CMI
The history of problems with split faced concrete block buildings:
As some of you may know, I have been inspecting, studying and writing about the issue and problems with houses and condominiums constructed using split-faced concrete block for many years. Here is a summary of the evolution of this issue and summaries of my work.
My first article explained the type of construction and the problems of water damage and mold:
The next article dealt with a new wrinkle, the effects of the water on the wooden structural floor and roof trusses:
This was followed by a paper on the problem of removing water that was being retained in the block, even after the sources of the water intrusion were fixed:
I then wrote an article on a new, innovative solution to the problem, highlighting the research that myself and others have been applying to this problem:
Then an article addressing the popular, “quick-fix” solution of sealing the block and why this does not solve the problem:
The disturbing new findings:
The other day, I was doing a water intrusion assessment for a condominium owner in Chicago, According to public records from the Building Dept., the building started construction in 2000 and had its final inspection in 2002. The building had 4 stories at the front and 3 in the rear with the top story unit having a duplex up space leading to a roof deck at the rear. I was inspecting the clay tile coping covering the parapet wall and noticed that the tiles had been incorrectly installed. The masons had just laid a line of mortar and slapped the tile down on top. as a result, the sides of the coping tiles, which usually have an open space to allow the wall to “breath”, were closed, clogged with mortar. The mortar joints were also cracked, typically, with age. The clay coping tiles serve two functions; a) To serve as sort of an umbrella and keep water from entering the wall and b) to allow any water that does enter the wall assembly to evaporate out through the vents on the edges.
Then I turned and looked back at the exterior side wall. It’s end was exposed as it only extended back half the depth of the building, providing a exterior side wall for the 4th story at the front. Running down the end side was a vertical crack. This crack extended from the top of the wall, all the way down to the lower parapet. There was also signs of efflorescence coming out of a cracked area, indicating that there was significant water in the wall. This crack ran vertically, down the length of the block and was through the entire block, not like the more commonly seen mortar joint cracks.
What was causing this crack?
BTW: It should be noted that the paint that is evident on the picture on the right was a cosmetic paint that the unit owner had applied. I mention this because many masonry contractors and builders seem to believe that “sealing” the block will stop all the water intrusion. As seen in the diagrams, below, this is definitely not the case.
Split block CMU (above) has air cells inside the block. This reduces the cost and weight of the block. These air cells can also be used for metal reinforcing bar placement and filled with concrete, but I have rarely seen this done in this area. The coping tile, stone coping or metal capping at the top of the wall should serve to keep water from entering the walls and filling these cells. Water in the cells can leak into the interior wall cavity and insulation, causing water damage, mold and even rotting of the support trusses (as we have seen in previous articles).
And here is the new concern. No coping or flashing system is perfect and the coping tiles or stones or metal capping are not ventilated, the wall cannot “breath”. Any water that does enter the wall assembly is trapped, not allowed to escape through drainage holes or evaporation. If the coping is cracked or not properly flashed, a significant amount of water can accumulate, filling these air cells.
During the winter, this trapped water freezes and expands (this is called the freeze / thaw cycle). The force of the this expanding water should not be underestimated. We see examples of the force of freezing water every day. Usually, they show themselves as minor cracks and openings occur in brick mortar joints and are easily repaired. Over time, brick walls have to be re-pointed, where the old mortar is ground out and new mortar applied.
But the situation with split faced block is much more serious. The expanding water in the air cells exerts so much pressure that it is, slowly, exploding the block from within. Once the block cracks, these openings will only get larger. With the connecting webs of block split apart, there is nothing to hold the block together laterally. As the two sides of the block move outward the block will loose its structural integrity and the wall assembly will fail. Simply put, with nothing to hold the exterior structural walls together, the building will collapse.
I have shared these findings with some Architects and Structural Engineers I work with and they agree that the this is a potentially frightening situation. People just do not expect newer, 10 – 20 year old buildings to fall apart.
So, what are the concerns, aside from the possibility of personal injury. What will the owners of these properties do? How do you sell a properly that is splitting itself apart? Who is responsible, and who is liable, for this problem? The Chicago Building Department, based upon Illinois Appellate Court ruling, has no liability. The developers of such properties will usually limit their liability by dissolving the corporate LLC they formed to build the building soon after is is sold. Will real estate agents even list these type of buildings. Will insurance companies continue to insure these type of buildings, they will not pay for the collapse damage because they attribute the damage to the builder’s errors.
As you can seen, this is a problem much more complex than just a little water damage and possible mold growth.
If you own one of these type of buildings, you can find contractors who can fix them and fix them properly. Look for the new “Split Block Certified” inspection logo. Making sure that the parapet wall flashings are intact and properly vented is the key. A professional home inspector who has experience with these types of problems could be your first step in the process.
As our company’s motto states, “Hope this helps.”