How Soil Make-Up Affects Foundations

Clay soil, comprised of tiny particles, is tricky because it expands when wet and shrinks when dry.

As the saying goes, a home is only as strong as its foundation. Homeowners want their homes built on solid foundations so that they don’t begin to experience problems over time.

But what about the support for the foundation itself?

Though it’s rarely given much thought, the truth is that a foundation also needs a strong foundation. That’s why the soil type around the home will make a massive difference in how its foundation performs.

A soil that is ideal for a building will provide good support. But sometimes homes are built with little thought given to the state of the soil. In fact, when a foundation is dug, the removed soil is replaced as a backfill. This backfill process can weaken the soil around the foundation and lead to concerns. The better soil type prepared and compacted as a backfill, the less likely a homeowner is to have foundation problems.

There are six different primary soil types that homeowners should know about.

Clay

Clay soil, comprised of tiny particles, is tricky because it expands when wet and shrinks when dry. The significant variations in this soil’s structure can put a lot of pressure on a foundation, causing it to move up and down. Ultimately, this can lead to cracks.

Rock

Rock foundations have exceptionally high bearing capacities, providing vital support. Variations of rock include limestone, sandstone, bedrock, and shale.

Peat

This dark brown/black soil has been formed by decomposed organic material. It is usually found near wetlands and is highly porous. Like clay, peat shrinks and expands frequently and is a poor support material.

Sand/gravel

Of all the soil types, sand or gravel has the largest particles. It is dry and does not hold moisture because of its large openings, so it does drain easily. If well compacted, sand or gravel can make good support for a foundation because of its inability to hold water. Even so, over time, sand particles can lose their friction and be washed away, creating a gap in the foundation. Homeowners can solve this with helical piers, also called helical piering.

Silt

Silty soil has smaller particles than sandy soil and is, therefore, smooth to the touch. It retains water longer because it is composed of tiny particles, but it is known to drain poorly. The expansion of silty soil will push against a foundation and ultimately weaken it.

Loam

This combination soil type is a mix of sand, silt, and clay. It is dark in color and soft to the touch. Because it handles moisture in a “balanced way,” it is a suitable soil type for foundations.

When a foundation fails

Homeowners who notice cracks in their foundation, bowing walls, or windows and doors that are sticking, then there’s a good chance that they’re dealing with a foundation problem, and, depending on the soil type, the soil could potentially be the culprit.

Whatever the case may be, it’s essential to call a foundation repair expert and have an inspection performed. While it’s tempting to let the issue, foundation problems will not resolve themselves. Instead, they’ll only become more problematic over time and at a more significant expense to the homeowner.

Accurate Builders of the Chesapeake provide foundation, basement, and crawlspace installation and repair for the greater Baltimore area homeowners.