How to Build a Gravel Pad for Your Sauna (Step-by-Step)

How to Build a Gravel Pad for Your Sauna (Step-by-Step)

A gravel pad is the most popular foundation for outdoor saunas and for good reason. It drains better than concrete, costs a fraction of the price, and you can build one in a single day with tools you probably already own. It's also forgiving - if you need to adjust things later, you can.

Here's exactly how to build one that'll keep your outdoor sauna level, dry, and stable for years.

Materials You'll Need

• 3/4-inch crushed stone or pea gravel (calculate volume below)
• Landscape fabric (woven geotextile, not the cheap thin stuff)
• Landscape timbers, steel edging, or treated 4x4s for border
• Landscape stakes or rebar for securing the border
• Hand tamper or plate compactor
• Shovel, rake, and wheelbarrow
• 4-foot level and string line

Choosing Your Gravel

Not all gravel is created equal. The two best options:

3/4-inch crushed stone - This is the top choice. The angular edges of crushed stone lock together when compacted, creating a surface almost as stable as concrete. It doesn't shift underfoot and stays put in heavy rain. Ask for "crusher run" or "road base" at your landscape supply yard.

Pea gravel - Smooth and round, pea gravel drains beautifully and looks nice. The downside is that it doesn't compact as firmly as crushed stone because the round pieces don't interlock. It can shift under heavy point loads. Works fine for lighter saunas on cradle supports.

Avoid river rock or large decorative stone. Anything over 1 inch is too big to compact properly and creates an uneven surface.

How Much Gravel Do You Need?

Make your pad 12 inches wider than the sauna footprint on all sides. For a sauna with a 7x7 foot footprint, your pad should be about 9x9 feet.

At 4 to 6 inches of depth (after compaction), here's how much gravel to order:

• 8x8 pad (4" depth): about 1 cubic yard
• 8x8 pad (6" depth): about 1.5 cubic yards
• 10x10 pad (4" depth): about 1.25 cubic yards
• 10x10 pad (6" depth): about 1.85 cubic yards
• 10x12 pad (6" depth): about 2.2 cubic yards

Order 10-15% extra. You'll need it for compaction settling and filling any low spots. Bulk delivery from a landscape supplier is much cheaper than buying bags at a hardware store - usually $30 to $50 per cubic yard delivered.

Step-by-Step Build

Step 1: Mark Your Layout

Use stakes and string to outline the pad. Double-check your measurements against the sauna's actual footprint. Square up the corners by measuring diagonals - when both diagonals are equal, your rectangle is square.

Step 2: Excavate

Remove all sod, roots, and topsoil within the marked area. Dig down 6 to 8 inches below your desired finished grade. You're creating a basin that the gravel will fill. Get down to mineral soil - any organic matter left underneath will decompose and cause settling.

Step 3: Grade and Compact the Subgrade

Rake the excavated area smooth. Use a hand tamper or plate compactor to firm up the exposed soil. If you're on a slope, grade the subgrade so it slopes slightly (1/8 inch per foot) away from any nearby structures.

Step 4: Install Landscape Fabric

Lay woven geotextile fabric across the entire excavated area. Overlap seams by at least 12 inches. Extend the fabric up the sides of the excavation. This prevents soil from migrating up into the gravel and keeps weeds from growing through.

Step 5: Install the Border

Set your landscape timbers, treated 4x4s, or steel edging around the perimeter. Stake them firmly. The border contains the gravel and gives the pad clean edges. Make sure the top of the border is at your desired finished grade.

Step 6: Fill and Compact in Layers

This is the most important step. Don't dump all the gravel in at once.

1. Spread 2 inches of gravel evenly across the pad
2. Compact it thoroughly with a tamper or plate compactor
3. Spread another 2 inches
4. Compact again
5. Repeat until you reach your target depth

Compacting in layers is what makes the pad solid. Skip this and you'll get settling within the first few weeks.

Step 7: Final Level Check

Use a long straight edge and a 4-foot level to verify the surface is level in all directions. Add or remove gravel as needed and re-compact any adjusted areas. You want less than 1/4 inch of variation across the entire pad.

Common Mistakes to Avoid

• Skipping compaction - The single most common mistake. Loose gravel settles for months. Compact every layer.
• Too shallow - Less than 4 inches of gravel doesn't provide adequate drainage or stability. Go 6 inches if your budget allows.
• No landscape fabric - Without it, weeds grow through the gravel within a year and soil mixes in from below, turning your pad into mud over time.
• Making the pad too small - Extend at least 12 inches beyond the sauna on all sides. This helps with drainage and gives you a clean area to walk around the sauna.
• Ignoring drainage - If the pad sits in a low spot that collects water, gravel alone won't fix it. You may need to re-grade the surrounding area or install a French drain.

How Long Does a Gravel Pad Last?

With proper installation, a gravel pad lasts essentially forever. The gravel doesn't degrade. The main maintenance is raking it level once a year and occasionally topping off any low spots - maybe a bucket or two of gravel per year if that.

Your outdoor sauna will likely need replacement before the gravel pad does.

Ready to Build?

A gravel pad is a one-day project that protects a multi-thousand-dollar investment. Get your materials delivered in the morning, and you can be sitting in your sauna that evening. Browse our outdoor sauna collection to find the right sauna for your new pad.