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What I Learned from Building an Outdoor Sauna with a Wood Burning Stove

Guest Post Series continues.  Part II with Russ, who first shared his corbel system to support sauna benches here.  And given his building skill and meticulous attention to detail, we thought it a good idea to bring Russ back to share:

What I Learned from Building an Outdoor Sauna with a Wood Burning Stove

  1. Plan the whole space, not just the sauna footprint. You’ll need a deck, patio or other lounging area to rest between rounds in the hot room. You may also want to install an outdoor shower of some sort – and that should be easily winterized if you live in a cold climate.
  2. Plan the interior of your sauna carefully, so that windows from the hot room see the outdoors directly, or indirectly through a window in the door to the hot room, which is aligned with a window on the world. Also consider cross ventilation in the changing room, including retractable screen doors that work well in confined spaces.
  3. Carefully consider whether you want to build an outdoor structure out of materials you procure, or hire a shed building company. There are many advantages to building your own structure, and much satisfaction from doing so. But it will take much longer than you think, if you aren’t a builder. Do-it-yourselfers will spend a lot of time seeking advice on materials and construction techniques, not to mention permitting issues and code requirements. They’ll also become very familiar with local lumber yards or big box stores, and they’ll need a truck to haul materials. Without a truck they may have to pay delivery fees for materials chosen by vendors, who may use this to dispose of materials no one would select for themselves.
    Would I built it again – YES! It was a lot of fun, and became a collaborative undertaking. Also, it justified purchasing new tools, e.g. a portable table saw for ripping. I already had a chop saw, but my executive committee readily conceded to my requests for new tools, and paid the freight.

    the principal Hanson Sauna builders: dad on the left, Russ in the center, and his son on the right.
  4. Whether you build a structure, or order one, site preparation is critical, especially – but not only – for the sauna structure itself. You need a site that will drain, but you also want one that is level for the structure itself. The right mix of gravel is the answer. Talk to locals who haul foundation gravel for a living. As for the sauna itself, I recommend installing a rodent screen of ½” x ½” wire mesh under the entire structure if you have woodchucks in the vicinity. Otherwise they will chuck all the wood a woodchuck can chuck, if a woodchuck could chuck wood. Your hot room may be too ventilated without this precaution.
  5. The pitch of your roof should be 6/12 or more. Otherwise you will be hard pressed to install the attic insulation shield that is a standard part of fireproofing for the chimney. The saving grace is that the AIS can protrude through the roof for a few inches, as the boot can accommodate it. FYI, with a steeper pitch the changing room can accommodate a loft, as Glenn shows in one of his designs.Russ’s 8×12 sauna ready for action on a late summer day.
  6. Before you panel inside the sauna – and before you insulate – settle on the location of light fixtures, switches, and outlets. Run the wire before you panel the inside of the sauna, even if your executive committee has not settled on exact locations, leaving enough wire to accommodate nearby locations. Do the same for speakers, although Bluetooth speakers make this optional.
    • More importantly, decide on a source of power. Solar and wind provide DC, which points in the direction of LED lighting, and more generally, DC appliances. This entails a controller and a battery, but no converter.
    • Solar or wind power can be run through a controller, and into a battery, and then be converted to AC. This is more expensive, and includes more parts that could fail.
    • AC power feed to the sauna is a third, and often the easiest, option – until you need to rent and operate a trencher, in order to comply with a dizzying array of codes for wiring detached structures. Note that detached structures may require their own load center, with 4-wire connections to a ground-fault breaker in the main box.
      Russ’s hot room interior.
      Note the meticulous bench construction.
  7. Within the sauna, make sure the hot room is only 7’ high, even if you double the top plate in order to interlock the wall corners. This will ensure good stapling surfaces for the foil, and nailing surfaces for cedar paneling. If you build your own structure, be sure to incorporate nailing surfaces for the ends of cedar panels.
    FYI, if possible, identify a local source of tongue and groove cedar, especially if that source allows you to pick your own boards. This is especially important for cedar 2” x4” lengths for your benches. You won’t find many knot-free 2”x4” at the big boxes.
  8. Record the location of your floor joists, so that you can avoid them when installing a floor drain in the hot room. A photo of the initial framing is helpful.
  9. Consider drip edges that cover the joint between wall and cement board for the flooring. This will require a slight bevel on the underside of the drip edge to accommodate the upward angle of floor boards sloping down to the drain.
  10. A squeegie is effective in leveling vinyl cement on horizontal surfaces, including cement floor boards, but also corner fireproofing before the cement boards are installed vertically.
  11. Don’t sweat the placement of the stove. Locate the chimney within the rafters, and then align the stove, having installed a pad of patio blocks broad enough to accommodate various stove placements. It is much easier to move the stove to the chimney than the chimney to the stove.
  12. Try to match the height of the duckboard flooring with the patio blocks under the stove and threshold into the hot room so as to minimize the chance of stubbing toes.
  13. Don’t sweat the elevation of the stove; it can always be blocked up on bricks or stone.
  14. Do sweat fire protection of the area around the stove. Two layers of cement board, separated by a gap of 1”, is recommended. Two layers separated by 2” on the ceiling is preferred. This is in addition to any heat shields on the stove.
  15. Burn oak, maple, and ash, if you can, in the sauna stove. Dispose of ashes responsibly. Some say ashes are good fertilizer for trees, but they also concentrate heavy minerals.
  16. Stack fire wood outside the sauna artistically, and preferably in the shape of fish, ships, or other nautical phenomenon. Give free reign to your artistic talents here, though you will have to take sides on fierce Scandinavian debates as to whether firewood should be stacked with bark side up or down!
    Russ’s 8×12 wood burning sauna stove almost completed and ready for action on a late summer day.

10 thoughts on “What I Learned from Building an Outdoor Sauna with a Wood Burning Stove”

  1. I would be remiss if I didn’t thank Glenn for encouraging and advising me while I built our sauna. I bought Glenn’s e-book, and then learned that it came with rapid, thoughtful advice in response to questions about how I ought to proceed –and warnings about what to avoid, or how different challenges might be surmounted. We have the sauna of our dreams, thanks to Glenn’s plans and his real-time advice, which no one else offers. So, the most important lesson I learned from building an outdoor, wood-burning, sauna is : Ask Glenn! He’ll advise, and most of all encourage, you how to build your own sauna, even if you live far from Finland.

  2. Like a good tennis match, I enjoy engaging with folks who are engaged with the sauna building process. Every once in awhile, someone comes up with a decent question or two, which may lead to a point of clarification, or an idea which I can better clarify in my ebook, which improves the book for the next sauna enthusiast.

    Goal: More kick ass saunas in the world (like Russ’s).

    Is it your turn?

  3. Hi,
    I’m building my sauna right now and I intend to use a wood burning stove. However, I can’t seem to find a definitive answer on internal/external wood feed. I would prefer to do internal feed but do I need to connect an air intake from outside the hot room? I’d appreciate any assistance on this issue.

  4. I have limited yard space and am using electric heat (I live in a cloudy valley and we choke out with out wood-burning neighbors in the winters). For ease of electric lines and privacy from the apartments surrounding, I’d like to build it half under a 60 foot cedar tree. Anyone know whether it’s ok to have the sauna shaded and partly under a tree? There would be limbs close to it and above it with a foot or so of clearance. Will the heat affect the tree?
    Can’t find any info on line; help appreciated.

  5. If you’re using an electric sauna stove, tree limbs close to your sauna building will have no effect. Tuck it in there and go to town.

  6. Love this site! I’m building a 5’ x 7’ sauna in a 16’x16’ screened porch that I’m converting into a three seasons room. Due to the perimeter necessary for a Kuuma wood stove, the low bench on the long wall will have to be short, lest it run too close to the stove. I have to put the door on the short wall, opposite the stove. I was thinking maybe I could run the low bench in an L with the short wall section having a piece that can drop down in front of the door when in use (either on a hinge or just a removable insert). Is this ever done, or too much of a no no from a safety standpoint (blocking the door)? Also, it looks like a 7’ ceiling is 1.5” too low for the Kuuma’s required clearance (53.5” above 32” tall Kuuma is 85.5” and my ceiling is 84”). I’d hate to have to raise the ceiling if I don’t have too. Finally, is the small or medium Kuuma best for this size sauna, given that it will also serve to warm the larger room by leaving sauna door open on occasion? Thanks! Glenn, I’ll ship you some beer once this project is over.

  7. I have a workman build an outdor sauna but he didn’t bother to prepare and level the ground so he build a pier foundation with high studs. The result is a sauna that is too far off the ground, it looks ridiculous. Help! Can he cut the posts/studs and lower the sauna, suggestions on how to do it? He is still finishing building …

  8. For sure, Patricia!!

    Do it now, or forever you’ll be holding your peace. Get that structure down as close to grade as you can. You’ll be stepping up and down ever sauna round from here til kingdom come. He can get a couple car jacks and borrow a steel beam. Take a deep breath and a sawzall and go to town.

  9. Great to hear…the sauna looks more like a shrine or a sacrificial site…ugh!!! Can the sauna be lowered without weakening the structure? How many men are needed to do it….he doesn’t want to do of course, but I am thinking holding off the last check until he does…

    What is a steel beam….so I get hold of one….ready to do it and thanks the encouragement, I won’t be happy for sure!

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