Two nearly identical 3–4 person saunas built right on existing covered decks near Donner Lake — no foundation, a big window on the view, and a heater sized for real steam.
In 2026 we designed two saunas for two different clients in Truckee, a few minutes apart near Donner Lake, and they came out almost the same building. Both owners had a covered deck with a view, both wanted a small sauna that sat right on that deck instead of a separate backyard structure, and both cared more about steam than gadgets. One is 7 by 7.5 feet facing Donner Lake; the other is 8 by 6 feet with a six-foot picture window aimed at Donner Summit, tucked under an upper deck. Each one is a self-contained, fully waterproofed box with its own framed floor that sits on the decking — no concrete, no digging. Inside, a two-tier cedar bench layout seats three or four on the top bench, a tall high-rock-capacity electric heater sits in the corner, and three vents keep the air moving. Because the two projects solved the same problems the same way, we turned the design into our Deck Sauna Plan so you can build one on your own deck.
Weight. A finished sauna this size with people, water, and a full load of heater rocks comes to roughly 2,500–3,000 lb in about 50 square feet. Decks are designed for load spread across the whole surface, not stacked in one corner. On both projects we put the sauna over beams and posts instead of the middle of a joist span, and had the deck framing confirmed before anyone ordered lumber. One of the decks was newly built, which made that easy.
Water from above and below. The 8x6 sits on a lower deck under a pervious upper deck. No snow load — but every rainstorm and snowmelt drips straight through the boards above. So it still got a full roof, sloped to drain past the edge of the deck rather than onto it. Both saunas get flashing at the railing and a gap under the siding so the deck boards can dry.
Building it in tight quarters. There's no room for a crew to swing full wall panels around on a deck with a house on one side and a railing on the other. We laid both out as a modular build — floor, walls, roof, and ceiling each framed and finished in place, then tied together — so a small crew or a handy owner can work through it one piece at a time.
Permits. The 8x6 owner called the Town of Truckee and was told a sauna under 120 square feet didn't need a building permit. The 240V heater circuit still went through a licensed electrician with an electrical permit. Every jurisdiction is different — read our sauna permit requirements guide and check with your building department first.
Materials for each sauna came to roughly $7,500–8,500, with the heater ($1,500–1,800) the biggest single item, followed by cedar, windows, and the door. With a professional build, both projects came in around $14,000–16,000 before the electrician and any permit fees. The window package is where these two moved the most — big custom glass costs real money and adds lead time, so order it early. Your numbers will shift with local lumber prices, the heater you pick, and how much of the build you do yourself.
Includes the layout, materials list, heater sizing, bench dimensions, and design notes — everything you need to use this project as a reference for your own build.
Deck Sauna Plan – 3–4 Person — $49
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Yes, if the deck can carry it. Both of these saunas sit directly on existing decks with no separate foundation — the sauna gets its own framed 2x4 or 2x6 floor that rests on the decking. The thing to check first is weight: a sauna this size runs roughly 2,500–3,000 lb fully loaded with people, water, and heater rocks, all concentrated in about 50 square feet. Set it over beams and posts rather than mid-span, and have a contractor or engineer look at the framing if you're not sure.
For three or four people, 7x7.5 or 8x6 feet is the sweet spot. That leaves room for a full-length upper bench (long enough to lie down on in the 8x6 version), a lower foot bench, the heater, and a door — while staying under 120 square feet, which can matter for permitting.
For the 8x6 sauna, the client checked with the Town of Truckee and was told a structure under 120 square feet didn't need a building permit. The heater's dedicated 240V circuit is still electrical work that a licensed electrician permits and installs. Rules change and vary by jurisdiction, so confirm with your local building department before you build.
Yes. One of these sits under a pervious upper deck — no snow load, but water drips straight through the decking above. So it still gets a full roof with underlayment and a drip edge, sloped to drain clear of the deck, plus flashing where the wall meets the deck railing so water can't pool against the bottom of the siding.
Both clients wanted heavy steam, so both designs use a tall, high-rock-capacity electric heater — the 8x6 uses a Harvia Cilindro. A big rock mass holds heat and gives you soft, lasting löyly when you throw water, which a small heater with a thin layer of rocks can't do. Size it for the room volume and any glass, and plan the 240V circuit early.
Materials ran roughly $7,500–8,500 including a $1,500–1,800 heater. Professionally built, both projects landed in the $14,000–16,000 range before the electrician. Building it yourself from the plan cuts out most of the labor.
If your deck is a different size, your view faces a different way, or you're not sure the framing will hold, we'll design one around your space — heater sizing, bench layout, ventilation, and the deck questions answered before anyone buys lumber. We work all over Truckee and Lake Tahoe.
Start the Design ProcessTahoe Sauna Company provides design and consulting services only. Construction is performed by the client or by an independent, properly licensed contractor hired directly by the client under a separate agreement.
12 decisions that determine how well your sauna performs — insulation, bench height, heater sizing, ventilation, and more. Get them right before you build.
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