Why South Jersey Soil Matters: What to Know Before You Dig Deck Footings

If you live in South Jersey — whether it’s Deptford, Mullica Hill, Washington Township, Marlton, Voorhees, Cherry Hill, Collingswood, Williamstown, or Berlin — you’ve probably noticed the ground isn’t the same everywhere. Some backyards drain like a champ; others stay muddy for days. Those differences matter a lot when you’re building a deck.

Your deck is only as strong as the foundation it sits on, and soil conditions across Gloucester, Camden, Atlantic, and Salem Counties play a huge role in how your footings should be designed.

Soil Types You’ll Run Into in South Jersey

South Jersey sits on the Atlantic Coastal Plain, and most towns — Deptford, Washington Township, Mullica Hill, Cherry Hill, Marlton, and even out toward Williamstown and Berlin — share similar underlying soils. The most common are sandy loams and loamy sands, which drain well and generally support deck footings without much issue.

But the region isn’t uniform. Parts of Camden County and areas closer to waterways can contain pockets of clay or silt, which hold water and lose strength when saturated. These heavier soils are more prone to movement, meaning footings may need to be wider or deeper to stay stable.

The key takeaway: even within the same town, soil conditions can shift from yard to yard. Proper depth, correct footing size, and inspections become critical to ensure the deck stays level over time.

What Soil Conditions Mean for Your Deck Footings

✔ Footings Must Reach Below the Frost Line

New Jersey requires deck footings to be at least 36 inches deep to avoid frost heave. When the ground freezes and expands, shallow footings can shift, causing decks to tilt, loosen, or pull away from the house.

✔ Load-Bearing Strength Varies by Soil

• Sandy/loamy soils → good drainage, good stability.

• Clay or silty soils → poor drainage, weaker support, higher chance of shifting when wet.

Heavier soils can require larger or deeper footings to carry the same load.

✔ Footings Need to Sit on Undisturbed Soil

Whether in Mullica Hill, Marlton, Cherry Hill, or Deptford, inspectors look for solid, undisturbed soil at the bottom of the footing hole. If the soil is soft, wet, or recently disturbed, it won’t pass.

✔ Standing Water = Red Flag

If water pools inside the holes or the soil collapses easily, wider footings or drainage adjustments may be required to meet code.

Why This Matters When Choosing a Deck Builder

Two houses on the same street can have different soil conditions — which is why cookie-cutter footing layouts can fail. At C-JAM Construction, we evaluate soil conditions before digging, choose the correct footing size and depth, and meet NJ code requirements across all the townships we serve.

That includes:

• Deptford

• Washington Township

• Collingswood

• Cherry Hill

• Voorhees

• Mullica Hill

• Marlton

• Williamstown

• Berlin

…and more across South Jersey.

Not sure if we build in your town? Check our Service Area or call us at 609-302-0249

Bottom Line

Building a deck in South Jersey starts long before a single footing is poured. Soil conditions, local permitting rules, and proper planning all shape how smoothly your project moves from design to completion. If you’re thinking about starting a new project, check out our guide on What to Expect When Building With C-JAM and our homeowner breakdown of How to Get a Deck Permit in South Jersey. Both resources walk you through the process step-by-step so you can feel confident long before construction begins.