Indoor Sauna Room Kit | Premium Quality Carbon Smart™ Sauna

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Authorized Retailer of Finnish Sauna Builders
Custom-Cut to Your Exact Room Dimensions
Manufacturer Warranty Included
Free Shipping on the Sauna Kit (heater ships at a weight-based rate)
Ships out in approximately 20–30 business days.
U.S.-Based Customer Support

The Carbon Smart™ Indoor Sauna Room Kit by Finnish Sauna Builders turns a 3' x 4' room with an 8' ceiling into an authentic Finnish sauna. Every interior component is cut to order for this room size and shipped as a crated kit: you provide the framing, insulation, electrical wiring, and exterior wall covering, and the kit supplies the rest — wall and ceiling paneling, benches, door, flooring, and finishing accessories.

Every Carbon Smart™ kit is made in Thermo Poplar, a thermally modified wood that is responsibly sourced. Choose an optional bench accessory package and a heater sized for this room to complete your configuration.

Who This Sauna Kit Is For

Homeowners converting a compact space such as a closet, a basement corner, or a primary bath into a dedicated 3' x 4' sauna
Contractors and remodelers building a custom sauna as part of a larger renovation
DIY builders who want precisely cut, room-specific components instead of sourcing lumber piece by piece
Spas, gyms, and wellness studios adding a traditional sauna room
Buyers who want the warm, even tone of thermally modified wood, with a choice of bench accessories and heater

Why Choose the Carbon Smart™ Sauna Kit?

Building a sauna from scratch usually means sourcing sauna-grade boards, a door, a heater, vents, and hardware separately — then cutting everything on site. This kit is made to order for your room size, so material quantities and cuts are worked out before it ships.

Finnish Sauna Builders is a Harvia premier partner that builds residential and commercial saunas across the U.S. Our team can help you choose the right accessory package and heater for your space before you order.

Key Features

Cut to Order for 3' x 4' x 8': Wall, ceiling, and bench components are sized for this room, not a generic fit.
Thermo Poplar Throughout: Walls, ceiling, benches, moldings, and duckboard flooring are all made in thermally modified Thermo Poplar.
Clear 1×4 Benching: 20" deep bench boards with supports, built to the configuration you choose from the product images.
All-Glass Sauna Door: Included with every configuration, with wood handles and trim.
Optional Accessory Packages: Bench Skirting, LED Under Bench Lighting, or the Luxury Package (both).
Room-Matched Heater Options: Choose a heater paired to this room size, or select "No Heater" to supply your own.

Thermo Poplar Wood

Carbon Smart™ saunas are made exclusively in Thermo Poplar. The wood is thermally modified at approximately 374°F, a chemical-free process that improves dimensional stability and resistance to humidity and temperature swings and gives it a warm, even tone. It is responsibly sourced to support carbon-smart forestry practices.

Thermo Poplar (only wood option)

Thermally modified poplar with a warm, even brown tone. Used for the walls, ceiling, benches, moldings and duckboard flooring.

Available Heater Packages

The heaters below are the options Finnish Sauna Builders pairs with a 3' x 4' x 8' room (approximately 96 cubic feet).

Heater	Power	Control	Notes
No Heater	—	—	Supply your own heater
Harvia KIP45W 4.5KW	4.5 kW	WiFi	Heater stones included
HUUM Cliff Mini 3.5KW	3.5 kW	WiFi	Heater stones and protective railing included

No Heater

The kit without a heater, for buyers supplying their own heater sized for this room.

Harvia KIP45W 4.5KW WiFi with Heater Stones

4.5 kW Harvia KIP with WiFi control for app-based scheduling, rated by the supplier for 176–353 cu ft. Heater stones included.

HUUM Cliff Mini 3.5KW WiFi with Heater Stones and Railing

3.5 kW HUUM Cliff Mini with WiFi control, rated by the supplier for 106–247 cu ft. Heater stones and a protective railing included.

Choose your accessory package and heater using the option selectors above. Pricing varies by configuration.

Accessory Packages

No Accessories

The complete kit as listed under What's Included, with open bench fronts.

Bench Skirting

Thermo Poplar boards that close in the front of the benches for a finished, built-in look.

LED Under Bench Lighting

Soft LED lighting installed beneath the benches. Supplier photo shows an example installation; room wood in the photo may differ.

Luxury Package: Skirting + LED Under Bench Lighting

Both upgrades together: closed bench fronts plus under-bench LED lighting. Supplier example photo shown.

Specifications

Brand: Finnish Sauna Builders
Product Line: Carbon Smart™
Product Type: Custom-cut (pre-cut) indoor sauna room kit
Room Size: 3' x 4' footprint, 8' ceiling
Room Volume: Approximately 96 cubic feet
Heater Options for This Size: 3.5 kW, 4.5 kW (or No Heater)
Wood: Thermo Poplar (thermally modified)
Wall & Ceiling Boards: 1×4 tongue & groove
Bench Boards: Clear 1×4, 20" deep, with supports
Door Frame: 27.2" × 78.7" (690 × 2000 mm)
Door Glass: 24.4" × 77.3" (620 × 1963 mm)
Door Frame Thickness: 1.65" × 3.6" (42 × 92 mm)
Rough Opening Required: 28" × 80"
Recommended Ceiling Height: 8' (per manufacturer safety and clearance guidelines)

Specifications are based on information supplied by the manufacturer and may be updated without notice.

What's Included

Foil vapor barrier for moisture protection
1×4 tongue & groove boards for walls and ceiling in Thermo Poplar
Clear 1×4 bench boards with supports (20" deep) in Thermo Poplar, built to your chosen configuration
Ergonomic backrests
Headrest
Corner moldings for walls, ceiling, and baseboards (Thermo Poplar)
All-glass sauna door with wood handles and trim
Duckboard flooring for the walk area (Thermo Poplar)
Upper and lower vent grills for air circulation
Traditional sauna bucket with liner and ladle
Sauna thermometer
Marine-grade, wall-mount, vapor-proof sauna light
Detailed installation instructions
Heater package and accessory package, if selected

Wall framing, insulation, electrical wiring, exterior wall covering, and items shown in lifestyle images are not included unless listed above.

Installation & Placement

Frame, insulate, wire, and cover the exterior of your 3' x 4' room with an 8' ceiling before the kit arrives.
Install the foil vapor barrier, then the tongue & groove wall and ceiling boards in Thermo Poplar.
Build the bench configuration you selected, including skirting or LED lighting if ordered.
Install the all-glass door (28" × 80" rough opening), corner moldings, and duckboard flooring.
Mount the vent grills and sauna light, then install the heater per its included manual. Heater wiring should be completed by a licensed electrician in line with local codes.

Note: Your kit includes an all-glass door, though some photos may show a glass wall for reference. Backrests ship flat; if you'd like an angled backrest, spacers can be made on site to set your preferred pitch.

Note: Wall boards run horizontally. If a wall is wider than 8 ft, an interior seam is added where two boards meet to span the width.

Care and Maintenance

Allow the sauna to cool fully before cleaning.
Wipe benches and walls with a soft, dry or lightly dampened cloth; a towel on the bench during use helps keep the wood clean.
Avoid bleach, harsh chemicals, and abrasive cleaners on wood or glass.
Leave the door open after use so the room can dry out.
Periodically check vent grills, the door seal, and the heater for wear or damage.
Follow your heater manual for stone replacement and heater-specific maintenance.

Shipping & Delivery

Shipping Cost: LTL freight shipping on the sauna kit is free. If you add a heater package, heater shipping is calculated at checkout based on the heater's weight. Ships within the contiguous United States only.

Production & Lead Time: Each kit is made on demand after your order and specifications are confirmed. Your estimated lead time is confirmed by email after the order is placed.

Freight Delivery: The kit ships as a crate by LTL freight to the terminal nearest you. The carrier will call to schedule a delivery appointment, and delivery is curbside with liftgate service. Crates longer than 92" may not fit a standard liftgate and may need to be unloaded by hand (two or more people) or with equipment. Please be available within 48 hours of the carrier's call, as missed appointments can incur storage fees.

Inspection: Count the pieces against the bill of lading and note any visible damage on the delivery receipt before signing. Report concealed damage or missing parts to Prime Regeneration within 72 hours of delivery, with photos, so a replacement can be requested.

Warranty

This kit includes a Finnish Sauna Builders manufacturer warranty. Coverage is subject to the manufacturer's written terms, eligibility requirements, exclusions, and claim procedures, and excludes normal wear, cosmetic changes, misuse, unauthorized modification, and damage from improper installation. Heaters are covered separately by their manufacturer's warranty. Contact Prime Regeneration before purchasing if specific warranty terms are important to your decision.

Returns & Cancellations

Because this kit is custom-cut to order, the manufacturer's made-to-order terms apply in place of our standard 30-day return window:

Cancellations within 24 hours of purchase are eligible for a full refund.
Cancellations after 24 hours are subject to the manufacturer's restocking fee, typically 35% of the purchase price.
Orders cannot be canceled once shipped, and custom-cut kits cannot be returned.

Contact Prime Regeneration as soon as possible if you need to cancel or change an order.

Important Wellness Information

Sauna bathing is not suitable for everyone. Consult your physician before use if you are pregnant, have a medical condition, or take medication. Stay hydrated, keep sessions moderate, leave the sauna if you feel unwell, avoid alcohol before or during use, and supervise children at all times. This product is not intended to diagnose, treat, cure, or prevent any disease.

FAQ

What is Thermo Poplar?
Thermo Poplar is poplar that has been thermally modified at approximately 374°F. The chemical-free process gives it a warm, even tone and improves its stability in the heat and humidity of a sauna.

Do I need to buy a heater with this kit?
No. Select "No Heater" if you're supplying your own, or choose one of the heater packages matched to a 3' x 4' x 8' room at checkout.

What do I need to provide?
Framing, insulation, electrical wiring, and the exterior wall covering. The kit supplies the interior paneling, benches, door, flooring, vents, light, and accessories.

What ceiling height does this kit require?
An 8-foot ceiling is recommended per manufacturer safety and clearance guidelines. Contact our team about custom ceiling heights.

How long does it take to ship?
Each kit is made on demand. Your lead time is confirmed by email after your order is placed.

How is it delivered?
By LTL freight as a crated kit, curbside with liftgate service. The carrier calls ahead to schedule your delivery appointment.

Can I cancel my order?
Yes, within 24 hours for a full refund. After that, the manufacturer's restocking fee applies, and orders can't be canceled once shipped.

Is shipping free?
Yes, shipping on the sauna kit itself is free. If you choose a heater package, heater shipping is calculated at checkout based on the heater's weight. Ships within the contiguous United States only.

Manuals & Documentation

Review the installation instructions before framing your room, and the manual for the heater or accessory option you choose. A printed copy of the installation instructions ships with your kit.