Masonry Building Problems in Chicago.

Many newer masonry buildings in Chicago suffer from "wet-building syndrome".

By William Decker, CMI

What is Split Faced Block and why was it used:

Split Faced Concrete BlockSince the mid 1990s, especially during the building boom of the early to mid 2000's, there were many new condominium buildings constructed in the Chicago area.  Many of these condominium buildings utilized a newer exterior masonry product that is commonly called split faced concrete block.  This material looked like an 8" thick common "cinder block", but had a rough face, making it look like stone (Right).  The material is manufactured using aggregate, Portland cement and course sand.  During manufacture, a complete 16" block is "split" in two so as form two 8" thick blocks, each with a rough face along the split edge.  The finished product resembles  rock-faced masonry in Richardsonian Romanesque houses popular in the mid-1880s (below).  But, as we shall see, prioritizing form over function can lead to long term problems when building houses.

Split faced block was commonly used as the exterior wall cladding on the sides and rear of 3, 6 and 8 unit condominium buildings and some single family houses  with the front of the buildings, usually, being covered with brick or stone.  "Was used" is the operative phrase because using this material in new construction residential buildings has, largely,  been stopped in the Chicago area, in late 2009.

Split faced block was chosen by builders for a number of reasons, but the biggest one was cost.  Here are the cost factors:

- Split faced block material costs are low.

- Being larger than a brick, it is quicker to lay and faster to install.

- This block is strong enough to use as a structural wall (i.e. a wall that actually supports the building) and attractive enough to use as an exterior cladding wall at the same time (this is, technically, what is called a single wythe wall, a wall that is only one layer of masonry thick).

- The material could be installed by less expensive, sometimes newly immigrated,  non-union masons.

Problems and Causes:

The problems seen with many split faced block buildings have been the result of water intrusion.  The symptoms include water stains and bubbling paint on ceilings and walls, warping and buckling hardwood floors, water dripping from exterior wall outlets and light switch boxes, musty smells and mold formation.  In extreme cases of long term water intrusion, the roof and floor joist ends get wet and rot.  This can lead to catastrophic structural collapse, where roofs and floors collapse!  It is important to realize that these are not the problems, they are merely the symptoms of the real problem which is water intrusion into and through the block.  Many times, home owners will have the roof replaced or "fixed".  When water is coming through your ceiling or walls near the ceiling, people logically thing that the roof is leaking.  I have many clients who had their roofs completely replaced, but the water kept coming in.  The best solution is always to solve the primary issue (the water intrusion) before addressing the secondary symptoms.

PLEASE NOTE: Many fly-by-night predators (and even some reputable masonry companies), seeking a quick fix and a quick buck, are going around promoting "sealing" the exterior of the block as the "easy fix".  While using water proof block or applying an exterior sealer may help in some cases, the block not being sealed is NOT the primary problem with these buildings.  It is only one factor, and a minor factor at that.  In my research I have found that only 8 - 11% of the water entering the building is coming in through the block, laterally.  There are many split block buildings that have never been sealed but have also never had water intrusion problems.  Each building is different in its construction and each building has to be evaluated based upon its individual construction details.  Quick fixes offered by the proverbial "two guys in white panel van" cost you money and time but do not fix the problem.

Why does the water come in?

To fully understand why split faced block houses and buildings have water problems, it is first necessary to understand how these buildings were built.  The first thing to understand is that all masonry is porous and absorbs water.  Brick, stone, cinder block and split faced block will all absorb water.  So why aren't all the old brick and stone houses having water problems?  The reason is that they were built with multiple wythe walls.  Multiple wythe (width) walls are actually two (and sometimes three or four) walls in one.  The inner one or two widths are structural and support the building's weight, while the outer wall (sometimes called a veneer wall) does not.  Between the inner and outer walls is an air gap, usually about 1" wide.  Water will travel in pretty much any direction, based upon gravity, pressure differences, humidity, capillary action and heat gradients, but the one thing that water will not cross is an air gap.  This is the biggest issue with split faced block buildings.  They were, almost always, built without an air gap as a single wythe walls.

Even when built in the single wythe configuration, split faced block buildings can avoid water intrusion problems if they are properly designed and built.  Looking at the diagram to the left, we see how a split faced block wall should be built, based upon building science best practices and industry standard specifications.  But these details are rarely used.

Coping flashing - The top of the exterior walls (also called the parapet) must be properly sealed.  The top of the wall is usually covered with a piece of stone.  This stone is supposed to keep rain water from entering the top of the wall and seeping through the masonry.  Think of an umbrella.  Many masons are not aware that this stone, itself, is porous and, given time, moisture will still get through.  Older buildings were constructed using limestone that was 3 - 4" thick and would dry out faster than the rain made it wet.  The newer product (which is much less expensive) is a small aggregate concrete block that is polished to resemble limestone (Renaissance stone) and is usually 1 3/4 - 2" thick.  It is also very porous to water.

Best practices call for the installation of a non-porous membrane of rubber or metal (called flashing) over the entire width of wall and under the coping stone.  This serves as a barrier to water intrusion.  This construction detail is crucial because the majority (70 - 80%) of the intruding water enters the wall through the coping stone.

Parapet wall ventilation - While the top of the parapet wall should be covered and sealed to keep water from entering the top of the wall, the wall itself should also be ventilated.  This is a classic construction technique that has been used for hundreds of years but seems to be lost to most modern Architects and Builders.

Ventilated parapet wall coping

Split faced concrete block wall

The blocks themselves have air cells inside (left).  If these internal cells are allowed to ventilate to the outside (above), to "breath", moisture that is in the wall will be able to evaporate and be less inclined to pass through to the interior.  This is was done in the older brick buildings in Chicago, where the parapet wall was "capped" with clay coping tiles and many of these buildings are over 80 years old and still in good condition.  The inside and outside edges of these tiles provided an air space that allowed the interior of the brick walls to breath.

Mortar and block cracks - Another concern is cracking of the mortar.  Intuitively, we think that big cracks in the mortar between the block will allow more water to enter the wall.  In fact, the opposite is true.  Big cracks do allow waster to enter, but they also allow this same water to drain out.  Small, hairline cracks are much more of a problem.  They do not just "allow" water to enter the crack, that actually suck it in through a process called capillary action.  Because the crack is so narrow, the surface tension of the water draws rain into the crack where it is soon absorbed by the blocks natural porosity.  Another problem with the mortar is caused by the employment of masons who do not understand the local conditions.  Many newly immigrated masons have a long tradition, "from the old country" to add extra sand to the already pre-mixed mortar.  They believe that this will make the mortar stronger, when it also makes the mortar more water absorbent.  Both these factors lead to water being absorbed into the block. 

Flashing - When building a house, all areas that can possibly allow water to enter the building should be, so to speak, waterproofed.  The problem is that almost impossible because most building materials (wood, stone, masonry, siding) are porous.  The exterior of a building is not "waterproof" but merely water resistant.  It allows waster to "shed" off the exterior surface.  These susceptible areas must be "flashed".  Flashing involves installing a water impermeable barrier (vinyl, rubber or metal) between the outside and the inside of the house, and between building materials of different water absorptive levels (i.e., between wood and masonry).  Flashing materials do not allow water (or water vapor) to pass through them and act to drainage plane to further shed any moisture absorbed in the wall down and out.  This is why some better built properties have the flashing, along with small pieces or rope (weep wicks, left) sticking out of the side walls at the level of the floor joists.

BTW:  Home Inspection Rule # 101: "Caulking is NOT flashing!".  Caulk will crack, come loose and deteriorate.  Any opening that is caulked (window and door frames, roof penetrations, bathtub / tile corners) must also have flashing of some sort behind the caulk.  Caulk alone will not stop water and, in most cases, is more cosmetic than functional.  Many times, in an effort to "fix" water intrusion problems, inexperienced workers will caulk an opening that should be left open to allow for water drainage.  This is commonly seen above windows and doors where the drainage space between the steel lintel and the block / brick is caulked or mortared shut.  Rather than stop water from entering the wall, it blocks the designed drainage opening and causes water to back up and drain down from the top if the windows and doors on the inside.

Joist flashing - The floors and roof of these buildings are supported by floor and roof joists.  Commonly, these joists are engineered wooden trusses, specially designed and manufactured assemblies that are much stronger than a normal solid piece of lumber.  They are usually constructed of lengths of 2 x 4 lumber secured with metal plates called gussets.  These truss joists are inserted into pockets in the block masonry walls.  There should also be a flashing membrane installed between the block and the wooden trusses to keep water away from the wood.  The truss should also be installed with supporting shims and there should be an air gap between the truss's wood and the masonry.  The membrane and the air gap both provide protection against water wicking into the truss.  It is never a good idea for wood to get wet or be in contact with masonry.  Problems occur when the builders, a) do not install the flashing properly and / or,  b) grout the truss end pocket instead of shimming.  In both cases, moisture from the masonry wicks into the wooden truss ends, rotting the wood and rusting the securing gussets.  As we shall see, later, this can lead to a very serious problem.

Exterior wall flashing - The other reason for the joist flashing is to catch any moisture that is draining down, within the wall, and direct it outward, away from the building.  This flashing membrane should be upturned on the interior side of the wall (so as to catch and drain the water outward)  and extend out of the exterior side of the wall, forming a drip edge.  The drip edge should extend, at least, 5/8" away from the wall.  Current national construction standards call for the exterior drip edges to be made of stainless steel or copper, for durability.

Many times, the masons (or the insulation sub-contractors) do not properly turn up the interior end of the flashing and this allows water to drain into the building, warping hardwood floors and causing tiles to crack.  Similarly, many builders fail to properly extend the exterior drip edge far enough outward from the exterior of the wall which allows the water (both already in the wall and water falling on the wall) to be sucked back into the masonry mortar.  It is am ironic circumstance that many builders do not install this flashing because the buyers will think it looks "ugly".  Functionality should always trump any cosmetics of a building and they should be designed to be properly appealing in the first place.


Exterior wall sealing - Contrary to common believe, sealing the block is NOT the final solution, but does help (BUT DOES NOT CURE) the problem.  While it is better to have the block sealed, it is not necessary if the building was properly constructed.  Sealing adds water impermeability to the block and acts to shed water off the surface.  When the exterior wall of block is not sealed, and depending upon local weather conditions, rain water and humidity in the air is drawn into the block.  This moisture travels through the masonry into the insulation and drywall.  It should be stressed that the majority (70 - 80%) of the water intrusion DOES NOT come, from the sides, through the walls but flows downwards from the unflashed parapet wall coping stones and stone window sills.  That being said, the moisture intrusion through the walls must not be ignored.

A curious phenomenon that we have observed, many times, is what is known as "solar loading".  Imagine a large building with split faced block sides and the south and / or west sides exposed to the sun.  It rains for a couple of days, not a hard driving rain but just a steady drizzle.  There are no water intrusion problems while it is raining.  Finally, the rain stops and the sun comes out.  After 4 to 6 hours (around 1:00 PM or so) water starts staining the interior wall and dripping through electrical outlet and light switch covers on the south side.  One wonders why the water didn't come in during the rain, but does when the sun is shining.

What is happening is that the sun is heating the exterior block wall.  Intuitively, one thinks that the sun will dry the water.  In reality, the sun is only "drying" the moisture on the very  surface of the block.  The rest of the water that has already been absorbed is actually being driven further into the masonry because the heat of the sun is expanding its volume, increasing the vapor pressure and further pushing the water that was already in the masonry out into the insulation, drywall and out the wall.  This condition is exacerbated by the the use of mid-efficiency forced air furnaces in many of these condominium units which draws a significant volume of air out of the building.  The negative interior air pressure works to actually suck the water in through the block.

It is interesting to note and contrary to common sense that masonry buildings, in fact, do most of their drying out during the winter, not the summer.  In the winter, heat moves outward from the heated interior living space.  As this heat moves, it pushes any moisture in the masonry ahead of it (heated water expands).  When this water reaches the exterior surface of the masonry, the cold, dry air causes it to evaporate. This sometimes leaves a white, fluffy powder on the outside of the wall.  This is called efflorescence and is the result of the outgoing water dissolving some of the lime in the wall mortar.  The water dries on the outside of the wall and leaves the lime.  Because of a couple of relatively warm (and wet) winters in our area, problems with water intrusion in masonry has been much more pronounced.

The old, commonly accepted best practices method of split faced block sealing used to be applying a "pigmented, silicone based,  silane/siloxane, penetrating sealer", but it has been found that such products only lasted 3 to 5 years (depending upon the manufacturer and the skill of application).  Many times, the sealing contractor has not been properly trained in how to apply the sealer, and the condition of many "sealed" buildings attests to this fact.  Silicone silane/siloxane sealers MUST be applied in a flood coat, completely covering the block and allowed to be soaked into the block.  Repeated sealing is also expensive,  Properly sealing a 3 story condominium building is expensive ($17,000 - 21,000, professionally done).  The current preferred sealing solution is a polyurethane or elastomeric based "plugger" type paint, installed by licensed, insured, trained and qualified masonry contractors.  This product will completely seal both the block and any small cracks in the mortar joints rather than just retard absorption and can last for 10 - 15 years.  But, this solution does not solve the larger problem and will NOT guarantee that the building will stay dry.

Drying out the retained moisture - When a split faced block wall has been exposed to moisture for a long time, it tends to retain (or "sequester") the water deep in the block.  Think of a wide sponge.  If you spray it with water it will absorb the water.  When the sponge's capacity to absorb the water is exceeded (in building science, this is called the "hygric buffer barrier") water will start leaking out the other side.  But, the water being leaked is NOT the same water that is being sprayed on the other side.  There is always going to be some water, "in the pipeline", so to speak.  Split faced block can absorb its own weight in water, and this retained water has to be removed.

Once the exterior walls and parapet have been properly flashed and sealed, no more water will enter the wall.  BUT, there is still a great deal of water that is already in the wall, and will not dry out because the exterior has been sealed against water getting in, and water getting out.

To fully solve the problem, the water that has already been absorbed in the masonry has to be removed.  This can only be done by greatly lowering the humidity levels inside the house, which will draw the water out of the masonry  through the insulation and drywall.  Remember, in a typical three unit, duplex down, condominium building with split faced block on the sides and rear, there is approximately 2,500 GALLONS of water that is still in the block.

This process requires time (3 to 4 weeks, depending upon the conditions) and multiple, industrial capacity de-humidifiers running, full tilt and 24/7, under closed building protocols.  This requires that the doors and windows in the house or building be kept closed (except for normal entering and exiting).  Many times, we have seen home and condominium owners who believe that once the cause of the water intrusion has been solved, they can just re-drywall and / or re-paint and everything will be fine.  They soon find the same water stains reappearing, sometimes in less than a week.  Solve the cause of the problem, then remove all the residual moisture before tending to the cosmetic details.  A car may have a really shiny and smooth paint job and cool chrome, but what really counts is what is under the hood.

Final steps - OK, we have solved the source of the water intrusion, and we have dried out the masonry walls.  Now we can "fix" the original problems that were the first complaint (i.e., water stains, puddles, mold growth, a "musty" smell, warped window frames, baseboards and window frames, etc).  Fine!

But how do we repair these problems, and do so following "best construction practices" (i.e., what the original builder should have done it in the first place!).

First, make sure that you have properly (and professionally) remediated any mold problems.  Mold, growing on porous surfaces like drywall and wood IS NOT KILLED!  IT HAS TO BE REMOVED!  Many people want to minimize the amount of repair needed and believe that they will just "kill" the mold and paint over it.  MOLD IS NOT KILLED, IT HAS TO BE REMOVED!  All the affected building materials (drywall, wood, insulation, wallpaper, etc) must be removed (torn out).  What cannot be removed (wall studs, structural members) must be professionally treated and encapsulated.  This is NOT a job to be done on the cheap or by non-qualified workman.  To do otherwise is to be inviting the mold to come back again.  Make sure that any mold remediation is done by specifically trained and certified workers!

DO NOT USE BLEACH TO CLEAN MOLD!  It will only make it worse.  Mold on tile, grout and other non-porous surfaces can be killed with bleach, but for porous surfaces (i.e., drywall, wood, insulation) you must use special means.  A good, over the counter product is Mold Control which is available at most home improvement stores and many people believe that they can save money by doing it themselves.  The best solution is to hire a professional, licensed, certified and insured mold remediation company.  There are plenty of guys out there who claim that they can clean mold, but you should always ask to see their credentials, licenses and insurance cover sheets and ask if they utilize a licensed industrial hygienist when making their remediation plans.  Also ask about their guarantee.  There is no state licensing or government required qualification requirements for mold remediation contractors.  Also make sure that, after the work is done, you have a "clearance test" done by an independent mold testing inspector.  Clearance testing is the only way to make sure that the mold problem has been properly completed.  Reputable mold remediation companies will come back and fix any problem, usually for free, if the clearance testing is positive.

Use the proper type insulation for the type of construction, and have that insulation installed properly.  Fiberglass and "blown-in" cellulose insulation is pretty much worthless.  We inspectors refer to cellulose insulation as "mold food".  Insulation should provide an effective "building envelope".  A building envelope serves as a barrier to heat (thermal insulation), but also to air leakage (cold air infiltration, in the winter, and cold air loss, in the summer), water intrusion (liquid water) and vapor movement (humidity, which will condense into liquid water).  This type of barrier can only be achieved with a foam type insulation and the easiest way to have foam insulation is the use of spray foam.

The two types of modern spray foam are open and closed cell foam insulation, and they are meant to be used in two different areas of the house.  Closed cell foam is used to insulate exterior walls.  Closed cell foam has small bubbles and will stop all water, vapor and air movement, as well as heat movement.  Open cell foam insulation has larger bubbles and will allow a small amount of moisture movement through the foam.  Why would one want to allow any movement of moisture through insulation, you ask?   Human nature being what it is, most people do not replace their roof covering until water in already dripping down through the ceiling.  By that time, however, the roof itself has already been leaking for a year of so, it just hasn't actually leaked through the interior ceiling (out of sight, out of mind).  If closed cell insulation is used to insulate the roof area, it will further retard roof leaks from dripping and will allow the water to be retained in the roof decking, causing rot and eventual roof structural collapse.  So roofs should be insulated with an open cell foam so that any leakage can be seen and the roof replaced before it becomes an even bigger problem.  Open cell foam also allows the building envelope to be extended, outward, from the ceiling of the top floor of the house to the underside of the roof decking, sealing any attic areas (the space between the ceiling and the roof) and better preventing heat loss (as well as stopping the natural "stack effect" of the house).

Finally, make sure that the interior drywall is properly installed and prepared.  Interior walls should be primed before painting. (And "paint and primer in one" products are just a bad joke.)  All door and window spaces (the air gaps between the windows and doors and their openings in the exterior walls) should be properly sealed (low volume foam).  And, it is always a good idea to properly control the humidity levels in the house.  Inside humidity levels should be kept between 25 - 35%, year round.  Use a de-humidifier in the humid seasons (in Chicago, remember, Summer, Fall and Spring are ALL humid).  A good rule-of-thumb is this:  If there is condensation on the inside of the windows, it is too humid.  If you get shocks when you touch metal objects, during the winter, it is too dry.  Buy and use a good humidity meter in the house.  It will help to keep the house comfortable and save you money in air conditioning electrical costs.

Final thoughts on the (possible) future:

The Home Inspector's quandary - As professional, licensed and certified home inspectors, in Illinois, we are called upon to serve our client's best interests.  This is usually done during the standard pre-purchase home inspection when a home is inspected for problems that may affect the client's willingness to buy the property.  But what does a home inspector do when they are discover the house or condominium unit that is clad with split faced block?  Not knowing if the building was completely flashed and or whether it was properly sealed, how can we best predict if your client's will have problems with water, mold and large repair bills?  How does the inspector properly protect the client?

The future, potential, calamity - With so many of split faced block houses and condominiums having been already built, and with the clear evidence that many (if not most) where not built (or, to be fair, maintained) properly, what is the potential, worse case scenario?  Long term water intrusion, through the block and parapet walls, can lead to water being wicked into the ends of the wooden roof / floor trusses and cause the trusses to rot or their gussets to rust.  The weight on these trusses will, eventually, cause them to displace (sag) or in extreme situations, break.  A catastrophic failure is possible! (although, we hope and pray that we are being overly cautious).   This will cause a portion, or all, of a roof or floor structure  to collapse down (called a pancake) onto the floors below.  Given the past history of Chicago buildings (rear porches and deck collapses, see here, from 2003, and here, from 2010, and here is the Illinois appeals court ruling, finding that no municipal code inspectors in Illinois have any liability whatsoever.  With the tragic loss of lives already seen, is a future disaster possible?  Given what we and other inspectors in the Chicago area have seen, this is a very real possibility.

Some years ago, a new exterior wall cladding material was also extensively used.  Called EIFS (Exterior Insulation Finishing System, usually referred to as Dry-Vit, the name of the primary manufacturer) it was sometimes cheaply installed.  This lead to many buildings suffering from mold and wood rot problems, and many homeowners having to pay for extensive repairs.  When installed according to the manufacturer's recommended instructions, EIFS is a very good product but, as we have seen, builders often cut corners to save money.

Many Real Estate agents, reacting to this situation, would automatically condemn any house that utilized EIFS, even if the product was properly installed.  To be fair, they were trying to represent their buyer's best interests, but in doing so that were writing off all EIFS clad buildings, without determining the building's actual condition.  But in doing so, they were also condemning thousand of EIFS properties to a scrap heap of houses that nobody wanted to buy.  I fear that Split faced block buildings will soon join that category.

To avoid this, as well as to avoid deaths and extensive property damage, it is very important that split faced block buildings be completely and professionally inspected and that condominium associations set aside the required funds to do the necessary maintenance of their split faced block buildings.  We would not want to see these properties turn into the newest wave of unlivable tenements.

As our company's motto states, "Hope this helps."