Settlement Cracks explained by John McLoughlin BSc (Hons)

I am a Degree Qualified, FEMA, ASHI & Certified Insurance Inspector with over 30 years of global experience in construction & building Inspection.

Throughout Florida many property owners experience cracking to their block construction properties. It is often thought that Settlement cracks are common in Central Florida. Unfortunately this is the case but with an understanding as to how the Settlement cracks appear and how to prevent existing cases from worsening it could save many Florida property owners money, time and hassle.

My experience and qualifications in worldwide construction techniques and fault diagnosis allows me the privilege to inform you. Together with being an ASHI Certified Inspector I am a university honors degree qualified Building Survey and Building Engineer with fellow membership of the leading worldwide construction associations & institutes.

• The Chartered Institute of Building www.ciob.org.uk
• The Association of Building Engineerswww.abe.org.uk
• The American Society of Home Inspectorswww.ashi.org

My qualifications and experience within the industry provide me with a unique competitive advantage to advice, help and assist on all matters relating to the construction and building industry.

The construction process starts with the most important part “The Foundation” this is unfortunately where the biggest mistakes are made leading to cracking of the blocks after construction.

Settlement happens when parts of a house drops below the elevation or height where they were placed during the original construction. There are numerous reasons why this may happen. There are several factors that need to be taken into consideration when making an evaluation and several main causes for ground settlement. Basically all properties that have settlement issues have to be evaluated individually taking into account all the circumstance and site conditions. I have listed the most common causes of settlement when dealing with Central Florida construction:

• Poor workmanship
• Poor supervision
• Low quality materials
• Lack of ground compaction
• Poor soil condition
• Bio degradable materials left under the construction site (dead wood, trees etc)
• Underground streams
• Sink holes

There are normally two types of cracks found when inspecting a property and not all home inspectors are aware of the significant differences although it appears obvious. Some home inspectors even fail to identify them within a standard home inspection report thus allowing the buyer to inherit a structural defect with long standing implications and resale devaluation on the property. The importance of identifying the defect is to allow either the owner/seller or the buyer of the property to identify it to the house builder and ensure it is covered under the builders warranty for repairs or rectification.

The weakest line of the structure is in most cases the mortar joint between the blocks. A Sheer crack is generally is a vertical or straight line crack not following the weakest line of the structure. A Sheer crack is an indication that the movement was rapid in nature compared with a slower movement or depression of the soil or the structure. A Sheer crack can be formed by either vertical or horizontal structural movement.  Rapid movement can cause the crack to be deeper than just a surface crack and in many cases will cut right through the concrete block. A major crack if left untreated will cause damage externally and internally. The photographs below show a settlement crack on the outside wall allowing considerable moisture to enter the inside wall of the garage. If this had been an internal wall with drywall it would have resulted in possible Mold growth as it would have probably gone unnoticed for some time. The cracking detailed below is a combination of Sheer and Stepped cracking.

This is the most common form of cracking identified in Central Florida while carrying out my home inspections. It is the cracking of the mortar between the block joint and generally takes and alternate step on the blocks and looks like the name itself as steps in pattern. They are generally seen more common at the corners of the building and eventually will run from the below the ground level to the entire height of the block wall. The crack is an indication of a slower movement of the structure or depression of the soil taking the weakest line of direction within the mortar joints.

As mentioned earlier in this article the causes for settlement cracking are numerous. The soil beneath the foundation or beneath the column supports may shrink due to moisture loss. The soil may not have been compacted properly before the concrete foundation was poured. Large pieces of organic material may have been included in the soil under the house, when it decays, the soil above it collapses to fill the void. The list of possibilities is nearly endless. But one very common practice has been observed by me while inspecting new construction homes in Central Florida and that is the lack of soil compaction is the main culprit to many settlement cracks. Many builders and home inspectors state that this is carefully monitored by “soil compaction tests” carried out by independent engineers and observed by a local building inspector. In the state of Florida there is a requirement for builders to perform soil compaction tests but unfortunately it is poorly monitored and there are few procedures in place to prevent an operative disturbing the soil or excavating it again for a forgotten pipe or service that should have been installed. When this happens it is seldom the builder will compact the soil again and have it re tested.

The most common mistake in construction causing settlement

The most common form of settlement is caused by incorrect compaction on the soil beneath the structure causing settlement resulting in Sheer of Stepped cracking generally to the ends and corners of the property. The reason for this is generally a result of poor workmanship or supervision by the construction team. When the construction footprint is marked out for pouring of the concrete slab the final stage should be to ensure the soil is compacted evenly. This is generally carried out by an operative either driving a heaving duty roller or hand pushed compactor over the entire area.  Unfortunately the corners of the footprint never seem to get as much compaction as the rest of the area because at this stage the operative is generally in the process of turning the machine to change direction thus failing to compact a critical area. The ground beneath these areas remains loose compacted soil and when the full load of the concrete slab is placed upon it, it will slowly start the sink downwards causing the blocks to crack above it.

So the statement that we hear often from builders is that “it is common for settlement cracks in Florida” is correct, but this is generally due to bad construction practice. Two types of commonly used ground compactors are the hand driven compactor and the driving compactor as seen below.

It is not just as simple as reviewing the sketches above to determine the exact cause of the cracking either by Settlement of Heave. Many other factors have to be considered when making an evaluation, particularly a review of the site history and conditions. Careful identification of any differential movement and displacement of any surrounding structure can also help identify and produce a true fault analysis.

How to reduce or prevent settlement cracking

In order to prevent or reduce the risk of settlement you need to be very pro active with your builder or the construction team. Strict monitoring should be adopted, the foundation and floor slab should be compacted just before the pouring of the concrete or as close to it as possible. Ensure the operative who is operating the compactor covers the complete area paying particular attention to the corners. When choosing the type of concrete is it always better to use the strongest and many home builders now use a fiber mix concrete which has additional strength over a conventional concrete mix.

When the concrete has been poured it is imperative that it is allowed sufficient time to cure and has adequate hydration. In the hot summer months concrete should be poured as early in the morning as possible and after the initial hardness cover is achieved a fine water spray should be directed over it to slow down the accelerated drying by the heat and sun. The minimum time the concrete should be allowed to cure is 7 days. This means not allowing the builder to place any weight or start building on the slab. The concrete should have expansion slots or joints cut into it as soon as a hard crust is achieved allowing it to expand and contract without cracking the surface. The exterior grading around the slab should be slopped away allowing any surface rainwater to be driven away from the structure. No deep excavations should be allowed near to the structure such as digging for a pool until the concrete is fully cured and the surrounding ground has stabilized.

Remedies to existing settlement cracking

All settlement cracking should be monitored for further movement. Settlement should be covered under the builders warranty and it will generally be their responsibility to rectify it if it persists. It is always advisable to get an independent evaluation carried out and present it to the builder. Once the problem has been identified monitoring tabs should be placed adjacent to the widest part of the cracking which will give an accurate indication of how fast and the extent of the movement.  All the cracks should be sealed with caulking to prevent water and insect ingress.

This one of the best monitoring devises available is a “Tell Tale” crack monitoring device. This glass or plastic slide rule type devise that is fitted securely over the crack. The exact location of the cross hairs in the scale window is recorded and reviewed after a period of time to determine exact movement.

If after an initial monitoring period of six months the crack has moved further, below ground investigation should be adopted by excavation to determine the cause. Replacement of the soil should be compacted in several layers and may also require back fill of additional reinforced concrete.

My home inspection services are unique within Central Florida area and provide the industry with a fully qualified professional at a market comparable cost far above the industry standard. In many countries whose construction techniques have been established hundreds of years such as the UK and Europe it is a requirement that the surveyor/inspector has a university degree in building technology, construction or surveying. Sadly in Central Florida no current legislation exists therefore the inspector you hire could have little or no training or experience in the industry to your detriment.

It is imperative that a fully qualified inspector is inspecting probably the most expensive asset you will ever purchase.

• Home Inspection
• Pool inspection
• New construction inspection
• Pre inspection
• Roof inspection
• 4 point inspection
• Home watch inspection

My full credentials and qualifications can also be verified online by reviewing my web page www.homeinspectionforyou.com or by contacting The American Society of Home Inspectors (ASHI) www.ashi.org, The Chartered Institute of Building (CIOB) www.ciob.org.uk and The Association of Building Engineers, (ABE) www.abe.org.uk

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