How to Make an Underground BBQ Pit - Outdoor Cabinets

Having your own DIY underground BBQ pit is the ultimate backyard upgrade for any grill master. An in-ground fire pit gives you more space to cook multiple items at once while keeping the party going strong. Building one does require time and elbow grease, but the end result is well worth it. Follow this guide to learn everything about constructing your own underground BBQ pit from start to finish.

Choosing a Location

The first step is picking the right spot to dig your pit. Here are some things to consider when selecting an ideal location:

Make sure there is adequate drainage so rainwater does not accumulate in the pit. Avoid low-lying areas.
Check local regulations about open fires and backyard structures. Many neighborhoods prohibit permanent fire pits.
Pick a spot at least 10 feet away from buildings, trees and other structures. This prevents fires from spreading.
Consider wind patterns so smoke does not blow right into your house.
Choose a place with easy access to water for extinguishing fires and cleaning.
Think about visibility and accessibility. Pick a social space where people can gather around.

Once you settle on the perfect spot, mark the ground with spray paint or stakes. Now comes the fun part – start digging!

How to Dig the Pit

Digging a large pit takes time and effort, but going the extra mile means you’ll have a stellar cooking space. Use these steps for how to dig an underground BBQ pit:

Gather Tools and Supplies

Having the right digging tools makes a back-breaking job much easier. Here is the essential equipment you’ll need:

Shovels – Invest in 2-3 rounded point and flat shovels. The variety helps with different digging tasks.
Mattock – The pick end breaks up compact soil while the wide blade scoops material.
Wheelbarrow – Transport dirt from the pit to dumping spot. Get a heavy-duty one.
Landscape Rake – Smooths out the bottom surface and removes rocks.
Measuring Tape – Marks out precise dimensions for clean lines.
Gloves & Eye Protection – Protect hands and eyes from loose debris.
Knee Pads – Reduces knee strain from kneeling on hard ground.

Optional tools that help are a pickaxe, chainsaw, sledgehammer, pry bar and post hole diggers. Having a few friends pitch in makes the workload lighter too.

Determine Size and Layout

Most underground BBQ pits range from 6 feet to 10 feet across and 2-3 feet deep. The dimensions depend on:

How much food you want to cook at one time. Larger pits hold more grills and food.
The weight capacity of your grill grate. Measure your existing grate.
How many people you plan to feed. More space offers flexibility.
Yard size and shape. Pick dimensions to fit the area.

We recommend an 8×8 foot square pit that is 2 to 2 1/2 feet deep for most purposes. This leaves ample room for a large grill grate and several people.

Use spray paint or flour to mark the pit’s outer edges on the grass. Outline the inner cooking area too if doing a stacked layout. We’ll cover pit designs next.

Choose a Pit Layout

There are two main ways to orient your DIY barbecue pit – single level or stacked.

Single Level Pit

This simple layout has one main grilling surface at the bottom. The advantages are:

Easier to construct. Just dig a square hole to desired depth.
Better heat control. Coals are right below the grate.
More headroom to maneuver food.

The downside is less overall grilling space. It works well for smaller gatherings.

Stacked Pit with Shelf

This two-tier design has a grill grate on the bottom plus a ledge around the top for additional grilling. Benefits include:

Doubles the cooking area.
Lets you prepare foods at two temperatures.
Easier to socialize around the pit.

The shelf is trickier to build but gives you more versatility. Choose this style if cooking for larger groups.

Start Digging!

Once you decide on a layout, it’s time to start digging. Here are some tips:

Loosen the topsoil first with shovels before using mattocks and pickaxes for harder clay or compacted dirt.
Use the wheelbarrow to dispose of dirt efficiently.
Establish a slope versus digging straight down walls so the pit doesn’t collapse. A 15-30 degree angle is optimal.
Make sure the bottom is level by measuring diagonally across corners. Use a rake to smooth it out.
Surround the pit with dug up dirt to create a natural “wall” barrier. Pack it down.

Take your time digging and don’t overexert yourself. Hydrate often and take breaks as needed. Carefully excavating the hole now saves headache later.

Building the Pit Structure

Once your pit is dug, it’s time start constructing the internal structure from cinder blocks and metal. Follow these steps:

Line the Inside Walls

Use standard 8 x 8 x 16 inch cinder blocks to line the pit walls. This protects them from collapsing.

Stack blocks lengthwise around the entire perimeter with the holes facing inward.
Stagger blocks for strength. Place binds between the blocks and fill with concrete for stability.
Leave a 2-inch gap between blocks and dirt walls for ventilation. This prevents smoke buildup.
Stack rows 3 blocks high for optimal heat resistance. Leave an opening for the chimney.

Lining the pit may take 100 or more cinder blocks. Purchase extra because some will crack or chip during shaping.

Build the Chimney

The chimney releases smoke and allows air circulation. Use large cinder blocks or bricks to construct a chimney at one end:

Make it around 16 inches square so it can ventilate properly.
Extend the chimney above ground level by 24-36 inches so smoke dissipates above seating level.
Cap it with a cinder block to prevent rain from entering.

Position the chimney on the side opposite the prevailing wind so smoke blows away from you. Place it near the top if doing a stacked pit.

Install the Grill Grate

Now comes the fun part – putting in the main grill grate! Here are tips for installing it:

Use an expanded metal grate designed for outdoor cooking. Stainless steel is best.
Measure inside dimensions to cut grate sections to fit. Allow 2 inches clearance.
Join pieces together securely with metal mesh welding or bolts.
Attach sturdy metal legs or angle iron edges to elevate grate 6-12 inches.
Ensure grate can handle weight of food, coals and tools. Opt for 3/8 to 1/2 inch thick grates.

Having a professional weld the grate is recommended for proper load-bearing strength. Custom size it precisely for your pit.

Add the Upper Cooking Shelf (Optional)

If doing a stacked layout, you will need to construct the upper cooking shelf:

Make shelving from heat-resistant materials like cinder blocks, bricks or concrete.
Extend the shelf 6-12 inches out around the inner pit perimeter.
Ensure bottom of shelf is at least 18 inches above the fire grate.
Surface the shelf with non-combustible material like steel or stone.

The upper shelf provides a flat surface for grilling sides, veggies and keeping food warm. Just be sure it allows enough heat ventilation.

Finishing Touches

Apply these final touches to complete your underground barbecue pit:

Install Ventilation Pipes

Adding a few vertical ventilation pipes brings in more oxygen and improves air flow. Use 8-10 inch diameter steel ducting. Insert pipes evenly spaced around the interior wall lining. Extend them a few inches above ground level.

Add Steps for Safety

Stack cinder blocks to create steps leading out of the pit. This prevents injuries from tripping. Make at least one stairway, preferably two.

Close Off Openings

Use extra cinder blocks or bricks to fill any gaps in the pit walls. This blocks wind from blowing into the pit and improves heat circulation.

Consider Accessories

Optional accessories like storage cubbies, work tables,umbrellas and lighting make your pit even more functional and inviting. Get creative!

With these finishing touches, your DIY underground barbecue pit is ready for grilling. Time for a backyard inaugural cookout!

Operating Your Pit Safely

Running a safe pit fire requires caution. Follow these tips when using your barbecue pit:

Only burn dry seasoned wood – never pressure-treated lumber which contains arsenic.
Open the chimney flue before starting fire for good ventilation.
Keep a lid nearby to extinguish flames if needed. Having running water on hand is ideal.
Don’t overload the pit with too much fuel and only use enough coals to maintain the target temp.
Monitor the fire at all times – don’t leave an actively burning pit unattended.
Ensure the fire is completely extinguished before leaving the pit unattended.
Dispose of cooled ashes carefully in a metal can. Don’t compost ashes from treated wood.

Adhering to standard fire pit safety precautions keeps your pit running smoothly for years.

Maintaining Your Underground Pit

Like any outdoor structure, your hand-built pit will require regular upkeep:

At the end of each season, remove grates and clear out ashes and debris using a shop vac or rake.
Check for damage to concrete blocks or grates. Repair cracks with high-heat caulk or replace damaged parts.
Use brick sealant to fill any small gaps that may expand over time.
Examine the upper cooking shelf for stability and signs of wear. Reinforce as needed.
Scrub grates thoroughly with a grill brush and coat with vegetable oil to prevent rusting.
Consider repainting or applying sealant to retain nicer visual appearance over time.

With proper maintenance, your custom-built underground barbecue pit will provide years of flawless grilling performance. The effort to construct it pays off every time you fire it up!

Frequently Asked Questions About Underground BBQ Pits

What is the easiest way to dig a large pit by hand?

Use a mattock and shovel to break up compacted soil. Then scoop loose dirt into a heavy-duty wheelbarrow for quick disposal. Taking small loads frequently is easier than giant scoops.

How deep should an underground BBQ pit be?

For safety and heat control, a depth of 2-2 1/2 feet is ideal. This leaves enough clearance under the grate while still concentrating heat. Make the pit wider instead of excessively deep.

What is the best wood to burn in a barbecue pit?

Dry seasoned hardwoods like oak, hickory and mesquite burn longest and impart great flavor. Avoid resinous woods like pine which can impart a turpentine taste. Never burn chemically treated lumber.

Should I line the inside pit walls with anything?

Yes, it is wise to line the dirt walls with cinder blocks or bricks. This prevents erosion and collapse while insulating the surrounding earth. Leave a small ventilation gap between blocks and dirt.

How much weight can an expanded metal grate hold?

It depends on grate thickness, but a 1/2 inch commercial grade grate can hold 500-700 pounds safely. For heavy cast iron Dutch ovens, opt for a 3/4 to 1 inch thick custom grate. Bolster support with steel angle iron.

What is the purpose of a chimney in a barbecue pit?

Chimneys improve air circulation by allowing hot smoke and gases to exit. This prevents food from tasting bitter. Chimneys also bring in fresh oxygen to feed the fire.

Should I cook with both top and bottom grates lit?

No, only light the bottom coal bed. The top shelf is for smoking foods indirectly above the coals, not directly over an open flame. Keep the upper area cooler.

How can I extinguish a barbecue pit quickly if needed?

Keep a lid or sheet metal plate immediately handy to smother the flames if necessary. For faster cooling, briefly remove the chimney cap to provide more air. Have a fire extinguisher and water hose on standby as well.

Conclusion

Constructing your own underground barbecue pit takes planning, hard work and time. But the end result is a showpiece cooking space that provides years of backyard grilling enjoyment. Now that you know the full process from choosing a site to proper operation, you can confidently take on this satisfying DIY project. With an in-ground pit, every barbecue session becomes a memorable party. Just be sure to follow safety precautions and maintenance tips to keep your custom pit in peak form. Go ahead and dig in – your dream barbecue oasis awaits!