DIY: Wood-Fired Hot Tubs

Chris Martini's first wood-burning hot tub on Mount Hood
Chris Martini's first wood-burning hot tub on Mount Hood
Photography by Northwest Timber Tubs

A few years ago, Chris Martini’s friends asked for help with a project. They had bought property at the base of Mount Hood and wanted to build a hot tub there. The only catch? The tub needed to be completely off-grid and fueled by a wood-fired stove.

Having extensive experience as a carpenter, and most recently managing production for a teardrop trailer company for five years, Martini thought the project sounded like a fun design challenge. “They sent me pictures of some fairly crude designs from the internet that they had found. Real simple stuff of an old tub with a copper coil set-up on the outside,” said Martini. “But the issue with that set-up is that it takes forever to heat up.”

Martini got to designing and building, not only the tub, but the platform beneath it, the stove insert, and a retractable roof that can be cranked open to see the stars, or closed to protect sitters from snow and rain. His friends were thrilled with the result. “After doing that, I thought, ‘This would be something fun to do for people,’” said Martini.

In 2020, Martini created Northwest Timber Tubs. For it, he builds his 58 Box Tub design, a 400-gallon volume, all cedar tub with a custom steel stove and firewood storage, which can fit up to four people for a soak. “A lot of people like the charm and the process of building a fire and running the tub that way,” said Martini.

Fencing off the stove to avert unintended bodily contact.
Fencing off the stove to avert unintended bodily contact.

He gave us the basics for installing a wood-fired tub in your backyard:

PICK A SPOT

First, always check local code requirements before starting any project like this.

The tub needs to be located in a flat and level area, with fifteen feet of clearance for the chimney. If placing the tub on a deck, make sure it can handle the weight with water. If clearing a spot on the ground, Martini likes to lay down river rock, as it’s nicer on bare feet than sharp gravel.

BUILD THE TUB

Martini builds his tubs out of cedar, using overlapping joints to avoid leakage, with stainless steel fasteners inside so there’s no rust. If your carpentry skills are limited, consider using a six-foot-wide stock tank tub and wrap it in wood for a finished look, like Martini did for the Mount Hood project.

FENCE THE STOVE

Martini designs and builds his own efficient stoves for his installations. There are also manufactured stoves available, like the Snorkel stove from Seattle. Just make sure the stove will be cordoned off from the rest of the tub by a fence – no one wants to accidentally graze hot metal while in relax mode.

FINISH AND SOAK

Apply a water-based sealant on the exterior wood, and nothing on the inside, so as to avoid the finish peeling off in the water. Once the fire gets going, use a paddle for dispersing the heat through the water. Sit back, listen to the fire crackle, and soak.

Martini uses overlapping cedar for a watertight and weather-resistant product, as in his 58 Box Tub design.
Martini uses overlapping cedar for a watertight and weather-resistant product, as in his 58 Box Tub design.

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