House Settlement Debunked

House Settlement Culprit - Note the vast differences in the thickness of the growth rings on the two pieces of lumber. The old-growth timber with the narrow bands experiences much less movement as it reacts to changes in moisture content. Copyright 2024 Tim Carter

House Settlement Debunked - Lumber Shrinkage Often, the Culprit

Roy subscribes to my free newsletter and reached out to me about a month ago for one of my phone consult calls. He needed help engineering a drainage system around his house to stop water from infiltrating his basement. I offer a house-drainage design service. I do a phone consult call and draw the plan to stop water infiltration into your home.

My college degree is in geology, with a focus on hydrogeology and geomorphology. Hydrogeology is the study of groundwater movement, and geomorphology is the study of the earth’s surface, where we walk and build things.

I shared how to stop the water infiltration. Roy emailed me a few weeks later to report my advice yielded a dry basement. He was very happy. He asked for additional advice based on some information given to him by a neighbor. All of a sudden we were on the topic of house settlement. His neighbor wandered into the murky depths of a topic that’s misunderstood and mis-diagnosed perhaps tens of thousands of times a day across the USA and the world.

It’s important to realize I could write a book about the topic of house settlement. It’s impossible to give it the respect it deserves in this tiny column. Years ago I wrote a column about house settlement you should read. I’ll attempt now to cover some of the most important aspects of the topic.

I pulled out my trusty paper dictionary and found that one of the many definitions of the word “settle” is “to cause to pack down.” This explains why many feel their house settles or sinks into the ground after it is built.

Bad Soil is Possible

Houses and buildings rarely sink or settle. Most soils are very strong. When a house or part of one sinks, it can be caused by landslides, earthquakes, uncompacted soil, buried vegetation that rots, expansive clay soil movement, glacial clays that ooze like toothpaste, etc.

Roy’s neighbor said settlement causes cracks in foundations that permit water infiltration. This is a true statement. However, most foundation cracks in poured concrete foundations are caused by shrinkage, not settlement. Concrete shrinks 1/16th of an inch for every ten feet of length as it cures over time. You’ll often see the cracks radiating at an angle from the corners of basement windows or any other hard 90-degree angle in an opening in the wall.

Concrete block foundations often develop horizontal cracks between layers of block, often about 4 feet up from the basement floor. These cracks are rarely caused by settlement. The cause can be traced to the inability of the thin mortar to withstand the tension forces applied to the wall. Remember, basement foundation walls are simply retaining walls holding back the earth outside.

The earth presses sideways against the walls and causes them to want to bend inwards. This bending force creates tension or stretching. If the block mason had filled the hollow cores of the concrete block with pea-gravel concrete and put a steel rod from the top of the wall to the footing in every other vertical core void, there’s a good chance there would not be a horizontal crack. Read this in-depth column about how to reinforce concrete block walls.

Mother Nature Compacts Soil on Her Own

Keep in mind that Mother Nature is very good at compacting soil. She uses both rain and gravity. Most soils are very strong, as evidenced by the countless hundreds of-year-old houses and buildings that have no structural defects related to soil movement.

I recall a job in Cincinnati, Ohio. Forty years ago I had to build a room addition on a home. The house was so old it had a stone foundation. My room addition floor had to be lower than the existing basement. I carefully dug along the old stone foundation trying to locate the footing. There was none. The builder just laid the first row of stone on the dense clay soil. The house was over 100 years old and had experienced no settlement of the foundation even with the concentrated load of the house on the soil.

Many new homes' cracks in the floors, ceilings, tile, drywall, woodwork, etc. are often blamed on settlement. In almost all cases, the cracks can be blamed on hybridized lumber. Trees are a crop not much different than soybeans and strawberries. The only difference is harvest time. Lumber companies, I believe, have engineered trees to grow faster so stands of timber can be harvested faster.

Spring Wood Causes Expansion and Contraction

Trees grow the most in spring. The wood produced at this time is lighter in color. The dark bands of growth you see at the end of a stick of lumber are summer wood. Summer wood is denser as the tree slows down its growth most often from a lack of rainfall in the summer. Old growth timber is markedly different. The spring and summer-wood growth bands are almost always the same size.

The more spring wood in a piece of timber, the more it wants to expand and contract as it experiences changes in moisture content. As the timber in a new home loses moisture, it shrinks causing the same tension cracks as happens in concrete. Things attached to the timber in your home then start to move creating cracks. These are shrinkage cracks, not settlement cracks.

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