Things to Know About Split Face Block

  • Split face block works on:

single story strip malls, warehouses, Big Box stores, and similarly industrial or mercantile structures.

  • Split face block doesn’t work on:

Multiple floor residential structure with wood floor platforms.  Most of them leak. Some leak a lot. I have looked at hundreds of split face block residential buildings and I’ve never found one that didn’t have moisture intrusion problems.  I do not know anyone that has worked on or inspected one of these buildings that hasn’t seen water problems.  The problem with this material and wood floor platform construction is the water leaks cause the joists and wood structure to rot.  The rot occurs where you can’t see it unless you open up walls, floors, or ceilings.

  • The problems are not necessarily with the block.

The problems are with the methods of construction. There’s nothing in the building code that prohibits it, but there are major problems with the methods of construction used in Chicago.  The codes that regulate split face block installations were not followed, and in some specific instances, the codes regulating split face block are simply wrong.  You cannot rely on an inspection that “certifies” the block as being satisfactory.

  • Major problems are often not visible.

The video was taken at a Lincoln Park house, beautiful, absolutely perfect in every way on the interior, nothing, no stains, didn’t read on IR, moisture measurements didn’t show anything, but this video shows the story.

  • The current method of repair involves sealant and caulk.  There isn’t any masonry industry body that approves sealant or caulk for masonry repair, let alone long term performance repairs.

Let me repeat……  There is no masonry industry code authoring agency or supervisory body that approves caulk or sealant for masonry repairs. I will grudgingly concede that sometimes these repairs “work”, but the repairs are, at best, temporary.  The “repairs” do not last. There are vast differences between sealant; some work OK, some don’t.  More importantly, these repair methods work against basic masonry engineering involving water management. Applying sealant is an attempt to turn these building envelopes into barrier systems. IOW, the repairs contradict how the buildings are supposed to function. See this related article.

  • Sealing masonry buildings with sealant and caulk can (and usually does) retain moisture in the floors, walls, or ceilings where you can’t see it.

The retained moisture causes poor interior air quality, mold growth (sometimes a LOT of mold growth), and structural damage.

  • The rodeo of waterproofing contractors currently “repairing” these buildings are not regulated.

There is no professional organization promulgating standards of practice, there is no license,  and it’s essentially a free for all of independent contractors making up their own methods for fixing these buildings with widely varying results.

  • We think there’s more than 20,000 of these things scattered all over Chicago.

In other words, there’s a lot of buildings with serious issues. This is becoming a well known problem.

  • This video from WickRight VRS explains it as well as anything I’ve found.

This topic needs a serious discussion.

And….coming to a building near you…..

These buildings have wood truss that bear on the block.  The truss are tree farm wood and highly susceptible to rot if they get wet.  They all get wet because they’re bearing on wet masonry.  They should be installed with a prophylactic sleeve or capillary break to isolate them from the masonry.  I, nor anyone I know, have ever seen any builder use sleeves or capillary breaks.  Like every other detail of split face block construction in Chicago, it’s wrong.

Note the method of assembly. The truss are bearing directly on masonry.  Note the rotten wood in the following pictures.  The two pictures of rotten joists bearing directly on wet block are not technically truss, but the pics illustrate the condition much better than the (extremely hard to access and photograph) truss ends. Different member, same problem, same results.

Wet interiors, rot, and mold is just the first chapter.  Rotting structural members is the next chapter.


I'm a home inspector and carpenter in Chicago and this site is built from things I’ve learned from 30 years inspecting houses in this town.

'Things to Know About Split Face Block' have 10 comments

  1. August 24, 2021 @ 3:43 am YV

    What’s the solution to a split block building?


    • August 25, 2021 @ 4:24 am Kurt Mitenbuler

      That’s a little too broad a question. Can you narrow it down a little?


  2. February 15, 2022 @ 1:23 am Alex

    After reading this, it seems that you would suggest to avoid purchasing a unit in a 3 flat that is build with split face block on the sides. Basically every single one will have these wood rot issues then, is that correct?


    • February 15, 2022 @ 1:40 am Kurt

      I will avoid answering the question as asked, as the State of Illinois prohibits my commenting on “advisability of purchase”. I can say unequivocally that I’ve looked at hundreds of them over 30 years time and never found one constructed correctly. No one I know in the HI business has found one built correctly. Dozens of my customers that purchased them…even after my damning reports…have had recurring long term water issues, with several requiring major repairs to the tune of tens, and sometimes hundreds, of thousands of dollars. The problems are well documented. It’s only the realtors and folks selling these things that don’t seem to know anything about the problems. Feel free to call me on my mobile if you want to discuss.


  3. August 13, 2022 @ 2:35 am YV

    What construction method alternative to split block would be optimal to deal with moisture and hold off leakages?


    • August 13, 2022 @ 3:26 am Kurt

      The $64,000 dollar question…. Cavity wall/double wythe drained assemblies are the established Gold Standard, except they are significantly more expensive to build. Due to City of Chicago building and fire code requirements, wood options can be limited, and depending on zoning and specific locations, may or may not even be approved for use. Wood frame assemblies are the only other viable cost effective alternative, but wood structures are subject to different codes in different administrative districts. It gets complicated in Chicago. I do want to make clear that split face block is appropriate if installed correctly and used in certain applications.. The problems come from the multiple opinions on what uses and applications are deemed appropriate and the definition of “correctly”.

      The “best” material is specific to the use, type, and location of a building. If you gave me the parameters and use, I could distill this down.


  4. October 29, 2022 @ 12:23 am Emily

    We are renting a property that is currently in the resealing process for the split block. My husband also just started to develop allergies and having trouble breathing. Does the resealing process pull the mold spores into the air?


    • October 29, 2022 @ 1:20 am Kurt

      I wouldn’t describe it as “pulling mold spores into the air”. It could be many things. Your husbands allergenic reaction could be mold. It could be reaction to the sealing chemicals. It could be that the sealing is holding moisture into the wall and increasing mold in your unit (the sealant holds water out, but it also hold vapor/moisture in). It could also be something totally unrelated and outside your home. It is hard or impossible to know what it is without knowing your husbands health and medical conditions.

      More is not known about how all these conditions “work”, than is known. Anyone insisting on absolute accurate information is mistaken. It is an evolving situation where we know more with passing time. I can say with certainty that there are many buildings that are highly problematic with mold and related moisture issues. Your building may be one of them.


  5. January 26, 2023 @ 2:05 am Staci

    Is there a possibility to use traditional brick on the outside of these buildings to act as a “layer” of protection?


    • January 26, 2023 @ 2:39 am Kurt

      Sure, you could do that, but it would entail all sorts of additional expensive rebuilding of details at windows, parapets, and elsewhere that would tend to preclude using an exterior brick veneer. If one was committed to redoing the building envelope, a stucco with drainage plane membrane or some similar draining substrate would be a better choice economically. Even wrapping it in vinyl siding with a drainage plane membrane would be better than what’s there, albeit it would be ugly as sin.

      Read my posts on “How Masonry Works” which will outline why just putting a brick veneer over it would entail a lot of steps most folks aren’t aware of.


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