Combustible vs Non-Combustible: The Part Most People Get Wrong

The single biggest misunderstanding in pergola grilling is what actually counts as “combustible.” Many homeowners assume that because the pergola is outdoors, or because it uses “composite” materials, the rules are looser. They aren’t.

Most pergolas are combustible. That typically includes:

• Wood beams, rafters, and posts (cedar, pine, redwood, etc.)
• Vinyl pergolas
• Composite pergolas (wood–plastic blends)
• Polycarbonate or acrylic roof panels
• Fascia boards, decorative corbels, and trim around the grill zone

Materials that are usually considered non-combustible include:

• Steel pergola frames
• Aluminum pergolas and shade structures
• Masonry, brick, block, and stone columns or walls
• Most concrete soffits or ceilings (verify finishes, paint, and trim)

Why this matters: your grill’s installation manual almost always lists two sets of clearances:

• Clearance to non-combustible surfaces (often tighter numbers)
• Clearance to combustible construction (wider safety margins)

If anything in the heat path is combustible — beams above, posts beside, siding behind — you must use the combustible clearance numbers. That’s why “my contractor said it’s fine” or “my neighbor did it” is not a safety plan. The only opinions that truly matter are your grill and hood manufacturers and your local codes.

Minimum Safe Clearances (Simple Rules Anyone Can Follow)

Clearances are the minimum distances your grill must maintain from anything that can overheat, melt, or catch fire. Every model is different, so you should always download and save the installation manual for the exact grill and hood you’re using.

That said, most premium built-in and cart grills follow similar patterns.

Side & Back Clearances

• Side clearance to combustible walls or posts: Many grills require at least 12–18 inches of space from side shelves or firebox to combustible surfaces.
• Back clearance: Often ranges from 6–18 inches from the rear of the grill to combustible siding, railing, or posts.
• Cutout installations: If you’re sliding a grill into a cabinet opening framed with wood, composite, or other combustible materials, an insulated jacket is usually required to safely reduce clearances.

Overhead Clearances

• Distance to pergola rafters, polycarbonate panels, or a solid roof: Many grills call for 36 inches or more to combustible materials above the cooking surface.
• With a hood installed: The hood has its own recommended mounting height, typically 30–36 inches above the grill, and then you must honor any additional clearance between the hood and pergola structure.
• Decorative lighting, fans, or heaters: These fixtures also have clearance requirements and should never hang directly in the hot plume rising off the grill.

If you place a grill closer than the manufacturer’s combustible-clearance requirements, you’re accepting avoidable risks: scorched beams, warped panels, melted finishes, and in worst cases, fire.

“We trusted the contractor instead of the manual. The overhead clearance was wrong, and heat warped the pergola beams in less than a month.”

Bottom line: Clearances are not a design suggestion; they are part of the safety system. Print them, highlight them, and design your pergola layout around them from day one.

Do You Need an Insulated Jacket? Here’s the Easy Answer

An insulated jacket (or grill liner) is a metal shell that surrounds a built-in grill. It’s lined and engineered to keep heat away from nearby framing and finishes. Think of it as a firewall between your grill and anything that shouldn’t get hot.

You almost always need an insulated jacket when:

• Your grill is installed in a wood-framed or composite-framed island.
• The island is tied into the house or a pergola post made of combustible material.
• You’re using any kind of vinyl siding, trim, or synthetic cladding close to the grill body.

You may not need an insulated jacket when:

• The grill is installed in a fully non-combustible structure (masonry/block with non-combustible finishes).
• You’re using a freestanding cart grill under a pergola and your clearances to posts/rafters meet the manufacturer’s outdoor/overhead requirements.

Insulated jackets provide three key benefits:

• Safety: They reduce heat transfer to framing and trim.
• Durability: They help prevent cracked stucco, warped fascia, or dried-out beams near the cutout.
• Inspection approvals: Many cities expect to see a manufacturer-approved jacket when combustibles are nearby.

Skipping the jacket to “save a few hundred dollars” makes no sense when you’re investing thousands into the grill, island, and pergola. If your manual calls for one, it isn’t optional.

Ventilation & Smoke Control Under Pergolas

Even in an open backyard, pergolas can act like a smoke trap. Rafters, shade panels, and low rooflines catch and hold hot air and grease that would normally dissipate into the sky.

Under a pergola, you’re usually dealing with two different types of ventilation:

• Island ventilation: Vent panels in the grill island that let gas and hot air escape from enclosed cavities — especially critical if you’re running propane.
• Overhead ventilation: A vent hood that captures smoke and heat rising from the grill and directs it away from beams, ceilings, and nearby seating.

If your grill is built into an island and sits under a pergola, you should assume you need:

• Properly sized vent panels (low for propane, higher for general airflow)
• A dedicated outdoor-rated hood sized for the grill and exposure
• Clear, unblocked paths for air to enter and exit the pergola space

Ignoring ventilation doesn’t just stain overhead materials — it makes the space uncomfortable to use. Grease-laden smoke hanging under the pergola is what turns a “dream kitchen” into something you avoid using on calm or humid days.

Practical rule: If the grill lives under a pergola — especially with any kind of roof panel or shade cloth — plan on a hood unless the grill manufacturer explicitly says it’s not required for your exact setup.

Hood Size, Depth & CFM: Beginner-Friendly Breakdown

Outdoor hoods have a tougher job than indoor ones. Wind, open sides, and higher BTU grills all fight against the fan. A basic “builder-grade” hood that might be fine indoors often underperforms outside.

Use these starting rules when sizing a hood for a pergola grill station:

• Width: Choose a hood at least as wide as the grill, and ideally 3–6 inches wider on each side. Example: For a 36" grill, look for a 42–48" hood. Under-sized hoods are one of the most common regrets.
• Depth: Outdoor hoods in the 24–30" depth range capture rising smoke much better than shallow designs that barely cover the front burners.
• Mounting height: Most outdoor hood manufacturers recommend 30–36" above the grill cooking surface. Too high and you lose capture; too low and you feel cramped while cooking.
• CFM (fan power): For a typical gas built-in under a pergola, many outdoor setups land in the 900–1200+ CFM range — especially for multi-burner, high-BTU grills.
• Filters and ducting: Look for baffle filters (good for grease capture) and as short and straight a duct run as possible to keep performance strong.

“Our first hood was too shallow and barely wider than the grill. Smoke just rolled out the front — it looked great and worked terribly.”

Think of the hood as a capture “umbrella” over the grill. If that umbrella is too small, too shallow, or mounted too high, smoke will escape into your pergola, no matter how strong the fan is on paper.

Pergola Types: Wood vs Aluminum vs Louvered Roofs

Your pergola material and design impact both safety and comfort. Different structures change how heat and smoke behave — and how strict your clearance plan needs to be.

Wood Pergolas

• Fully combustible: Beams, rafters, posts, corbels, and trim all count.
• Often require larger overhead clearances plus a properly sized hood.
• In many layouts, a grill liner / insulated jacket is strongly recommended for built-ins nearby.
• UV and weather can dry wood over time, making it even more sensitive to heat.

Aluminum or Steel Pergolas

• Non-combustible framing is a big safety win, especially overhead.
• Still requires attention to powder-coat finishes, lighting, and nearby accessories.
• Clearances are often governed more by the grill and hood manuals than the pergola frame itself.
• Excellent option for tighter spaces where wood clearances would push the grill too far out.

Louvered Roof Systems (Motorized)

• When louvers are closed, the system behaves like a solid roof with gutters and drip edges.
• Smoke and heat can build up quickly if the louvers are partially closed over a grill.
• Plan to treat these as a covered grill location that almost always deserves a hood.
• Grilling with louvers open may reduce heat buildup, but clearance rules still apply to any nearby combustible elements.

Whatever pergola type you choose, the process is the same: identify what is combustible, pull the grill and hood manuals, and design to those numbers — not to the sketch in your head.

Weather, Wind & Smoke Movement

Your grill and pergola don’t exist in a vacuum. Wind, temperature, and humidity decide where smoke goes and how comfortable the space feels.

Useful rules of thumb:

• Prevailing wind direction matters: If the wind usually comes from one side of your yard, try to position the grill so smoke moves away from main seating, doors, and frequently open windows.
• Polycarbonate or shade covers trap heat: Clear or tinted panels and dense shade cloth dramatically reduce vertical airflow. That’s great for shade, but it increases heat and smoke buildup under pergolas.
• Afternoon sun amplifies heat: West-facing pergola grills can feel much hotter at 4–6 pm. Good ventilation plus overhead clearance make the difference between “usable” and “unbearable.”
• Calm days are deceptive: On still evenings with little breeze, a weak or undersized hood will struggle most.

If you’re unsure, stand under your pergola at the time of day you expect to grill most. Notice wind direction, sun angles, and where smoke would go. Then design to make that experience better, not worse.

Smart Layout Tips for Pergola Grilling

Once you understand clearances and ventilation, the layout is about flow: can you cook, move, and serve without dodging beams, smoke, or guests?

• Keep the grill away from pergola posts: Posts are often structural and expensive to modify. Give yourself breathing room so heat and smoke don’t bake the column.
• Protect the “hot zone” walkway: Avoid placing main traffic paths directly behind the grill where hot lids and flare-ups are within arm’s reach.
• Give yourself 18–24" of landing space: On at least one side of the grill, plan for raw food trays, seasoning, and cooked food. Under a pergola, you don’t want to juggle plates on the grill lid.
• Use non-combustible finishes near the grill: Tile, stone, and properly rated panels directly around the cutout help buffer heat from nearby posts and beams.
• Separate “cook” and “hang” zones: Keep lounge seating and dining slightly downwind and out of the splash zone so guests aren’t forced to inhale smoke every time you sear.

The simplest rule for pergola layouts? Design around safety clearances and airflow first — aesthetics second. When you start with pretty 3D renders and try to force safety into them later, you usually end up compromising on both.

Common Pergola Grilling Mistakes People Regret

A few patterns show up over and over once real homeowners live with their pergola grill setups:

• Putting a grill under a pergola with no hood: It looks clean until the first few big cooks — then the rafters discolor, the ceiling smells like grease, and guests get smoked out.
• Assuming “it’s outdoors, so clearances don’t matter”: The same BTUs that would damage an indoor cabinet will also damage a pergola beam if it’s too close.
• Ignoring the insulated jacket requirement: Sliding a hot grill into a wood-framed, stone-faced island without a jacket is asking for hidden heat damage.
• Placing the grill directly under low beams or louvered panels: Heat and smoke get trapped inches above the hood, even when you have decent fan power.
• Locking in the layout before talking to a pro: Homeowners approve renderings, pour concrete, and only then ask a contractor or inspector to review the plan.

The cost to fix these mistakes is almost always higher than the cost to design it right the first time. Think one extra week of planning, not one extra summer of regret.

FAQ & Related Guides

Further Reading from Solavi Living

For more help planning a safe, long-lasting outdoor kitchen, explore these guides:

• Outdoor Kitchen Buying Guide
• Outdoor Kitchen 101: The Complete Beginner Guide
• Outdoor Kitchen Design Ideas
• Outdoor Kitchen Design Resources