What is Split Block construction? What are the problems with Split Block construction? Split Block, also known as “Split Face” block construction is a type of concrete block that gained popularity in Chicago in the late 90’s and was used primarily during the construction boom through 2008. Split Block was mostly used on small condo buildings that housed between 3 and 12 units. Below is a photo of the block.

What exactly is split block? Split Face Block is a masonry block which is split during the manufacturing process creating a jagged looking “face” which looks like natural stone. The block itself is relatively large and very sturdy.

Why was split block used? Split block is cheaper than traditional brick. Because of its large size it is quicker to install but still strong enough to be used as a structural wall. Because of its large size and basic shape even inexperienced masons can lay the block so labor costs are not only cheaper because of less hours needed to install but you can also hire individuals at a lesser pay per hour. It was a perfect product to be used during the real estate boom for developers who needed to build quick and wanted to watch their bottom line.


NO!! As a Realtor I tell my clients “There are many things to think about when buying a home but nothing to worry about.” You simply need to do your due diligence and you’re starting it now by reading this blog. Here are some items you need to know about split block and what to look for when you’re initially walking through a condo built with such a product.

Split Block is Porous! You might say “Well Duh! All Bricks are Porous!” While this may be true here is the issue with split block. When you build a traditional support wall out of standard brick you typically have a two layered wall with a 1 inch gap of air between the bricks. The reason for this is to keep water out of your home. Water can soak through anything, but the one thing it cannot do is magically cross an air gap. With split block however, this is not done. With split block construction studs are typically placed right up against the block. If water is soaked through the block like a sponge then the studs, insulation and then drywall also start to take in water.

How do you prevent this?

1. Proper tuck pointing. Sometime small cracks appear around the block. Many times inexperienced contractors will say the small cracks are nothing to worry about but in reality the small cracks are worse than the larger ones. One might think that larger cracks will allow more water in. While this is true the large cracks also allow water to flow out. Small cracks actually suck water in through a process known as capillary action. Once the water is sucked through these cracks it enters the block and so on and so forth.

2. Sealing: All Split Block NEEDS TO BE SEALED! There are two different types of products on the market but long story short the buildings need to be sealed every 5 to 7 years or so. They should be inspected however much more often. When you are looking at split block constructed condos have your agent ask the condo association when the split block is sealed. If the association says “Ummm what does that mean?” Then you might want to be very cautious moving forward. If the association says “We had it sealed last year” then you know you have a proactive condo association.

Flashing is important! What is flashing? Flashing is a piece of metal, typically aluminum that is placed in areas where water can penetrate the brick. Now there are many areas in a condo building where flashing should be used but here is one where it has typically been forgotten with regard to split block construction: THE TOP OF THE WALL!

So lets say we have a 3 story wall built of split block. At the very top of the wall we need a covering because water can soak into the block. Builders will almost always place a stone on top of this block in order to cover the block (plus it has a nice architectural look). The problem is that yes, that stone is porous too! What is so very important is flashing! A piece of flashing must be installed between the top stone (known as a capstone) and the concrete block so help push water away from the split block.

Do you remember a few paragraphs up when I said one of the advantages of Split Block was the fact that inexperienced masons could install it? Well, this is one of the reasons why split block gets a very bad reputation. More often times than not the issue with split block is not the product itself but the poor installation of the product such as the lack of flashing used!

What should I look for in a Split Block constructed building?

1. Look for warping of floor boards around areas that could have been poorly installed such as windows or sliding balcony doors, etc.

2. Look for water intrusion around electrical sockets and junction boxes. Why? Electrical wiring is run through conduit which is a metal pipe. Many times these pipes run horizontally overhead and then vertically down a wall. If water enters it many times will run along a smooth surface such as conduit.

3. Look for water/mold around ceiling corners. Why you ask? These are the areas where joists and beams enter the supporting exterior wall. These are areas were water can easily travel to first since water can be absorbed by wooden joists.

4. WALLS THAT GET THE MOST SUN ARE THE BIGGEST PROBLEM! Many people may think when the sun comes out it will dry up the brick and poof – no problem at all. WRONG! If a wall is wet and the sun then comes out it warms the block and therefore increased the vapor pressure on the block pushing the moisture into the block and into your home. These walls are the ones which must get special attention!

Why Shouldn’t I avoid Split Block?

There is no reason to avoid it. Some Realtor’s may tell you that you need to avoid the buildings but that is because they are not familiar with the product. “We fear what we do not know.” What you need to be is aware. I tell all my buyers to simply be aware, ask the right questions and take your time when inspecting a property. It really is that simple.


Paul Blackburn is an Illinois licensed Realtor and Associate Broker with @ Properties. He can be reached anytime via e-mail at Paul@PKBlackburn.com  For further information about buying a property in Chicago please contact Paul at anytime and visit his website dedicated to answering questions and explaining situations like the one above



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