Best Firewood Types for Heating Your Wood Fired Hot Tub

The crack of a well-seasoned log catching flame, steam rising off the water as the temperature climbs, stars emerging overhead while you wait for that perfect 104°F—this is the wood fired hot tub experience at its best. And it all starts with what you're burning.

The wrong firewood means more smoke, longer waits, and constant trips to the woodpile. The right firewood means you're soaking in 90 minutesThe wrong firewood means more smoke, longer waits, and constant trips to the woodpile. The right firewood means you're soaking in 90 minutes with nothing but an armful of wood to keep you there all evening. Here's how to choose it, source it, and burn it for maximum heat with minimum hassle.

Why Your Firewood Choice Matters for Wood Fired Hot Tubs

The best firewood for a wood fired hot tub is dry, dense, seasoned hardwood with moisture content under 20%. Oak, ash, maple, and birch all fit the bill—they burn hot, burn long, and get your water to soaking temperature without filling the air with smoke. The wrong wood, meanwhile, means more time waiting, more trips to the woodpile, and a haze that drifts toward the neighbors.

Here's the thing: hardwoods and softwoods do very different jobs in the firebox. Hardwoods are denser, so they pack more energy into each log and keep burning steadily while you're already soaking. Softwoods catch fire quickly and burn hot for a short burst, which makes them perfect for getting things started but not so great for the long haul.

Once you understand that distinction, everything else falls into place. The right wood, properly dried and strategically used, means less tending and more time under the stars with hot water doing exactly what it's supposed to do.

Best Hardwood Types for Maximum Heat Output

Hardwood is the workhorse of wood fired hot tub heating. It's denser than softwood, which translates to more heat energy per log and longer burn times between reloads.

Oak

Oak burns extremely hot and keeps going for a long time, making it a favorite for those sub-zero evening soaksOak burns extremely hot and keeps going for a long time, making it a favorite for those sub-zero evening soaks when you want the fire to do the heavy lifting. Both white and red oak work well, though they take longer to season than other hardwoods—often 18 months to two years before they're ready.

Ash

Ash is the all-rounder. It burns clean, splits easily, and performs reasonably well even when it's slightly less seasoned than other hardwoods. If you can only stock one type of wood, ash is a solid choice.

Birch

Birch is popular across Nordic countries for hot tub heating, and for good reason. It delivers solid heat with a pleasant, subtle aroma that adds to the whole experience. One thing to keep in mind: birch bark contains oils that can contribute to creosote buildup if you burn bark-heavy pieces exclusively, so mixing it with other hardwoods works best.

Maple

Maple provides steady, reliable heat that's perfect for maintaining temperature during long evening soaks. It coals well, meaning the fire keeps producing heat even as it burns down. Less babysitting, more relaxing.

Beech

Beech burns extremely hot with excellent coaling properties, making it a top choice for harsh winter conditions. It's harder to source in some regions, but if you can find it, beech is worth stocking for the coldest nights of the year.

When to Use Softwood for Your Hot Tub Fire

Softwood isn't inferior—it's just built for a different job. The key is knowing when to use it rather than relying on it as your main fuel.

Softwoods ignite quickly and burn hot for a short period, which makes them ideal for the fire-starting phase. Once you've got a strong flame going, you transition to hardwood for the sustained heat that actually brings your water to temperature.

Pine

Pine makes excellent kindling. It ignites fast, burns hot initially, and fills the air with that familiar campfire scent. Use it to get your fire roaring, then add denser logs on top.

Spruce

Spruce is light and quick-burning, common across Canada and readily available at many cabin properties. It works well for building that initial heat before transitioning to hardwood.

Cedar

Cedar splits easily and produces a pleasant scent—fitting, given that your tub is likely clad in the same beautiful wood. Like other softwoods, it works best as a fire starter rather than your main fuel source.

Fir

Fir burns cleaner than pine with less resin, making it a good transitional wood between your kindling phase and your hardwood phase.

How Much Wood You Need to Heat a Wood Fired Hot Tub

The amount varies based on your starting water temperature, ambient conditions, and tub size. Here's a practical framework:

• Initial heat-up: From cold water to soaking temperature (typically 100-104°F), expect to use several armfuls of split hardwood. A well-designed tub with an internally submerged firebox and proper insulation can reach temperature in about 90 minutes.

• Maintaining heat: Once you're at temperature, keeping it there requires surprisingly little—often just an armful of wood per day if your tub has adequate insulation.

• Cold weather adjustments: Sub-zero conditions demand more fuel, but a tub with triple-layer insulation dramatically reduces consumption compared to poorly insulated alternatives.

Firebox design plays a significant role here. A larger, internally submerged fireboxFirebox design plays a significant role here. A larger, internally submerged firebox transfers heat directly to the water rather than losing it to the surrounding air, meaning less wood burned per soak.

How Dry Your Firewood Needs to Be

"Seasoned" wood is wood that has been dried—typically for six months to two years—until its moisture content drops low enough for efficient burning. This matters more than almost any other factor in your firewood selection.

Wet wood hisses, steams, and produces excessive smoke. Quality dry wood burns clean with minimal smoke output, which keeps your evening peaceful and your neighbors happy.

Here's how to tell if wood is properly seasoned:

• Weight: Seasoned wood is noticeably lighter than freshly cut wood.

• Cracks: Look for cracks radiating from the center on the cut ends.

• Sound: Knock two pieces together—dry wood sounds hollow, while green wood sounds dull and heavy.

Moisture in wood absorbs heat energy that would otherwise go into warming your water. Wet wood also creates creosote—a tar-like substance that builds up in your chimney and firebox, reducing efficiency and creating potential hazards over time.

What Wood to Avoid in Your Hot Tub

Some materials have no place in your firebox, regardless of how convenient they might seem.

Treated or Painted Wood

Never burn treated lumber, painted wood, pallets, or construction scraps. These release toxic chemicals when burned—harmful to breathe and potentially contaminating. This includes pressure-treated deck boards, old fence posts, and anything with visible paint or stain.

Green or Wet Wood

Beyond the smoke and poor heat output, green wood accelerates creosote buildup in your chimney and firebox. That buildup reduces airflow, decreases efficiency, and creates a fire hazard over time.

Resinous Softwoods as Main Fuel

Pine and spruce work well for starting fires, but relying on them as your primary fuel leads to sticky residue and faster creosote accumulation.

Driftwood and Salvaged Lumber

Driftwood contains salt that corrodes metal components over time. Salvaged lumber may hide nails, screws, glue, or chemical treatments that aren't visible on the surface.

How to Heat Your Wood Fired Hot Tub Faster

Getting from cold water to soaking temperature efficiently comes down to technique as much as wood selection.

1. Start with dry kindling and softwood

Build a base of small, dry kindling—thin splits, newspaper, or fire starters—topped with quick-burning softwood. This establishes a strong initial flame that can ignite your denser hardwood.

2. Use split logs instead of rounds

Split wood exposes more surface area to the flames, igniting faster and burning more completely than whole rounds. Aim for pieces roughly the width of your fist.

3. Maintain steady airflow

Keep the firebox door crackedKeep the firebox door cracked during ignition to feed oxygen to the flames. Fire needs air—restrict it too early and you'll smother your progress.

4. Add hardwood once the fire is established

Once you've got a strong, roaring fire, transition to dense hardwood. This is where your sustained heat comes from.

5. Keep the lid on between checks

Heat escapes through the water surface faster than anywhere else. Keeping your cover on while heating can cut your time to temperature significantly.

How Firebox Design Affects Wood Efficiency

Not all wood fired hot tubs burn wood equally. The design of the firebox—and the insulation surrounding the tub—determines how much of your firewood's energy actually ends up in the water.

An internally submerged fireboxAn internally submerged firebox sits directly in the water, transferring heat immediately rather than losing it to the surrounding air. External fireboxes, by contrast, heat water indirectly and lose significant energy in the process.

Insulation matters just as much. A tub with multiple insulation layers retains heat far longer than an uninsulated alternative, meaning less wood to reach temperature and less wood to maintain it, especially in cold conditions. Firebox capacity also plays a role—a larger firebox accommodates bigger logs and requires less frequent reloading.

Sourcing and Storing Firewood for Year-Round Soaking

A reliable firewood supply takes planning, especially at remote properties where delivery isn't always an option.

• Where to source: Local firewood suppliers, cutting your own (where permitted), or bulk delivery for properties with road access. At the cabin, you might supplement with deadfall from your own land.

• Stacking and covering: Store wood off the ground on pallets or rails, covered on top to shed rain and snow but open on the sides for airflow.

• Seasoning timeline: Wood cut this year is typically ready next year. Plan ahead—the best time to stock up is well before you actually need it.

• Location near the tub: Keep a dry supply close to your hot tub for convenience, especially during winter soaks when you don't want to trek through snow for each reload.

Built for the Fire and the Wild

The ritual of splitting wood, building a fire, and watching the temperature climb is part of what makes a wood fired hot tub so different from the humming, glowing spa experience. It's slower, more intentional, and deeply connected to the outdoors.

That ritual works best when your tub is designed for it. An oversized, internally submerged firebox means faster heating and less wood per soak. Triple-layer insulation means the heat stays where you want it—in the water—even when temperatures drop well below zero. Marine-grade aluminum means you can fill from the ocean, the lake, the river, or the hose, and the tub will handle it for decades.

Reserve one today and discover what happens when the right firewood meets a tub built for the fire and the wild.