Why use rock wool instead of fiberglass in a sauna?

Fiberglass slumps under repeated heat cycling and holds water. Rock wool is fire-resistant, water-repellent, and stays in place. In a room that runs at 196 degrees Fahrenheit, that difference determines whether the wall assembly survives. Most sauna kits use fiberglass.

Does a sauna need a vapor barrier?

Yes. A continuous aluminum foil vapor barrier with taped seams across the walls and ceiling is what prevents steam from driving moisture into the wall cavity. Without it, moisture condenses inside the assembly on every cooling cycle and degrades the structure from the inside, while the cedar surface still looks intact.

Do I need a permit for an outdoor sauna in California?

Almost certainly yes. A sauna contains electrical work, and electrical triggers a building permit in California regardless of the structure's size. Bedrock Sheds pulls the permit under CSLB license #1087479 and handles the inspections.

What heater does Bedrock use in a custom sauna?

Harvia or Huum, at the buyer's choice, with stones, in either a floor-standing cabinet or basket style, sized to the room volume.

What is the difference between a custom sauna and a barrel sauna kit?

A barrel kit is a prefabricated shape assembled on whatever surface it is set on, insulated by the thickness of the wood, and usually built without a vapor barrier because a barrel has no wall cavity to protect. A site-built sauna is a framed room on a reinforced foundation, insulated with rock wool, sealed with a taped foil vapor barrier, ventilated, wired, and sized to the space and the number of people using it.

Can a sauna and a shed be built as one structure?

Yes. Bedrock builds combined structures with two doors and two separate rooms, with a sauna on one end and storage on the other, sharing one foundation, one roof, and one exterior finish.

Custom Saunas

Yeah, Saunas Too

Exactly to your requirements. Exactly to your space. Every sauna we build is drawn, planned, and built for the person who’s going to use it — right down to the bench height.

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Western red cedar sauna interior with two-tier L-shaped benches, Harvia heater with stones, and slate tile floor

The Build

Five layers, outside in

A sauna runs at 196 degrees with steam in it. The wall is what decides whether the building survives that. Here’s ours, in the order it goes together.

The structure

The same site-built shell as our sheds — reinforced foundation, 2×4 framing at 16 inches on center, structural plywood on every wall and the roof, a real roof system, Hardie Board Cement Siding, primed and painted. A sauna is a building before it’s a sauna, and most of what goes wrong with them goes wrong here.

Rock wool insulation

Not fiberglass. Fiberglass slumps with repeated heat cycling and holds water — in a 196-degree room it’s the wrong material, and most kit saunas use it anyway. Rock wool is fire-resistant, water-repellent, and stays where you put it. Walls and ceiling.

A sealed foil vapor barrier

Full aluminum foil across the walls and ceiling, every seam taped. Nothing else in the wall does this job — insulation doesn’t, cedar doesn’t, house wrap on the outside doesn’t. An untaped seam is just a hole with foil on both sides of it. Ask any sauna builder to show you a photo of theirs before the cedar went up. Over the foil we run furring strips, which create the air gap the cedar hangs on so the boards can breathe and move. Cedar nailed flat to foil cups and splits.

Western red cedar

Tongue-and-groove, walls and ceiling. It doesn’t get hot enough to burn you, it holds up to the heat cycling, and it smells like a sauna is supposed to smell.

Flooring and bench

Decide the material, decide the configuration, and decide the lighting. Floor in tile, sealed concrete, or wooden duckboards. Benches cut and assembled on site, at the height and depth that fit the people using the room. LED accent lighting under the benches. This is the layer that turns the room into your ultimate relaxation experience.

And the things that aren’t optional: a dedicated ducted vent, cedar louver high and intake low, because a sauna that doesn’t dry out between uses goes bad · LED accent lighting under the benches.

Two Rooms, One Building

The shed-and-sauna build

Most people who want a sauna also need the garage back. So we started building both into one structure — sauna on one end, storage on the other, two doors, one roof.

It came out of a real job. A customer wanted both and didn’t want two buildings taking up the yard. One foundation instead of two. One roof, one paint color, one crew, one schedule.

If you want a sauna and you’re also out of storage, ask about it — it’s usually the better answer.

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Backyard sauna building with sage green Hardie lap siding, cedar door and single-pitch roof

Pricing

What does a custom sauna cost?

We don’t publish sauna prices, and we’ll tell you why.

A shed has four standard sizes and one spec, so we can publish a grid and stand behind it. A sauna doesn’t work that way. Room size, bench plan, heater, floor, door, freestanding or attached — all of it moves the number, and none of it is a standard option.

For reference, a custom site-built sauna runs in the range of a small remodel, not the range of a kit. If a barrel kit is your budget, we’d rather tell you that here than after a site visit.

A barrel kit and a prefab cabin come in the sizes they come in, and you fit your yard around them. Neither one knows anything about your grade, your access, or how tall you are. We do it the other way.

How you get a real number

Tell us what you’re picturingSize, how many people, freestanding or attached, and what your yard looks like.

We talk it throughTen minutes. We’ll tell you honestly whether we’re in the right range for each other.

We come look at the siteAccess, grade, where the vent runs, where the door should face.

We draw your plansCustom drawings for your sauna — the room, the bench layout, the heater placement. You see exactly what you’re getting before anything is ordered.

You get a written numberItemized, with the plans and the spec attached.

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Questions People Ask

Saunas, specifically

How long does a sauna take to build?

Longer than a shed. The shell goes up on the same schedule, then the interior is careful work — the vapor barrier and the cedar are the parts nobody should rush. We’ll give you a date range in writing before we start.

Do I need a permit for a sauna?

Yes. We pull it under our license, CSLB #1087479, and handle the inspections.

Can you build it attached to a shed?

Yes. That is the shed-and-sauna build above: one structure, two doors, two rooms, one foundation and one roof. Freestanding is the other option, and it sits wherever the yard makes sense.

What heater do you use?

Harvia or Huum, your choice, sized to the room.

What are my options for the floor, the door and the window?

Floor in tile, sealed concrete, or wooden duckboards. Door in black-framed glass with a digital control, or solid cedar. Window, or no window. Room size and shape are yours as well. None of it is a menu you pick from, and none of it costs extra to ask about.

How high are the benches?

Whatever height fits the people using the room. Bench height and depth get set for you, not to a standard that fits nobody. If you lie down in a sauna, we build for that. If two of you sit and talk, we build for that as well.

Do I see it before you build it?

Yes. We measure the spot, then draw the room. How many people actually use it, where the door swings, how you get to it from the house. The plan comes back to you before anything is ordered, so you know exactly what you are getting.

Electric or wood-fired?

We can do either, but everyone chooses electric. It’s simpler to permit, simpler to vent, and it’s what every sauna we’ve built runs on. Ask us about wood-fired and we’ll tell you honestly what’s involved with venting and clearances in a residential yard.

Why rock wool instead of fiberglass?

Fiberglass slumps with repeated heat cycling and holds water. Rock wool is fire-resistant, water-repellent, and stays where you put it. In a 196-degree room, that difference matters.

Do you build sheds too?

Sheds are what we do most. See the sheds.

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Ask about a sauna

Tell us what you’re picturing and where it would go. We’ll talk it through, come look at the spot, and draw it.

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