FAQ: Modular Thermowood Sauna — Expert Answers to 8 Key Questions 2026

❓ Question 1: How long does a sauna made of thermally modified wood actually last?

📊 Short answer: 25–50 years with proper maintenance.

🔬 Scientific justification:

Thermal modification at 215°C changes wood at the molecular level:

1. Breakdown of hemicellulose → removal of "wood sugar"
2. Lignin crystallization → rigid cell wall
3. Fixing humidity at a level of 3-5%

Result : the wood becomes “biologically inert” – microorganisms, fungi and insects cannot feed on it.

📈 Service life comparison table:

🧪 Scientifically proven : Research by VTT Technical Research Centre of Finland confirms that Thermo-D thermally modified timber has rot resistance class 1 according to EN 350 – the highest safety level.

💡 Engineer's advice:

"Even the most durable material needs basic care. Wipe down the benches after use, ventilate the steam room, and check the roof once a year—and your sauna will last as long as possible."

❓ Question 2: Does thermally modified wood need to be stained or treated every year?

📊 Short answer: No, annual treatment is not required.

🔬 Why thermally modified wood doesn't require constant maintenance:

• ✅ Hydrophobicity : Water absorption 3–5% (versus 10–15% for regular wood) → water simply flows off
• ✅ Color stability : Pigments do not wash out, the color does not fade quickly
• ✅ UV resistance : Thermal modification increases resistance to solar radiation.

🎨 What we use for exterior coating:

🔄 When is it time to update the coating:

• If the color has lost its saturation (visual assessment)
• If the surface becomes rough to the touch
• Once every 5–7 years for prevention (optional)

💡 Lifehack : No need to sand thermally modified wood before repainting! Simply clean off any dust and apply a new coat.

❓ Question 3: Will there be cracks or distortions in the doors (shrinkage)?

📊 Short answer: No, shrinkage of thermally modified wood is <1% - this is "zero shrinkage" in practice.

🔬 Physics of the process:

Regular wood contains 12-22% moisture. When dry, it:

• Decreases in volume → cracks, seam divergence
• Deformation is uneven → distortion of doors and windows

Thermally modified wood after treatment at 215°C :

• Humidity: 3-5% (fixed)
• Shrinkage: <1% (not noticeable to the eye)
• Geometry: stable for decades

📐 Actual parameters for a 7×2.7 m sauna :

🔧 Structural solutions that enhance stability:

• ✅ Tongue and groove joints of boards - mechanical blocking of deformations
• ✅ Reinforced frame made of 100×50 mm timber – structural rigidity
• ✅ Metal fasteners with anti-corrosion coating - reliable connections

💡 Expert advice : If you notice minimal gaps (1–2 mm) after installation, this is not a defect, but rather a natural "breathing" structure. These gaps do not affect thermal insulation or airtightness.

❓ Question 4: How to prepare the area for the arrival of the bathhouse ?

📊 Short answer: A solid foundation is not required. A level base with drainage is sufficient.

🏗️ 3 recommended foundation options:

📋 Step-by-step preparation instructions:

1️⃣ Determine the location:

• Distance from the fence: ≥1 m
• Distance from home: ≥3–5 m
• Crane access: width ≥3 m, height ≥3.5 m

2️⃣ Site cleaning:

• Remove vegetation
• Remove the fertile soil layer (10–15 cm)
• Level the surface (difference ≤3 cm per 7 m)

3️⃣ Installation of the base (according to the selected option)

4️⃣ Waterproofing of contact points:

• Place roofing felt in 2 layers between the foundation and the bathhouse.

5️⃣ Connecting utilities (optional before the bathhouse arrives ):

• Electricity: cable 3×6 mm², panel, earthing
• Water/sewage: PPR/PP pipes with a 2 cm/m slope

🎁 Bonus from Thermowood : After ordering, we provide a free drawing of the support points with precise dimensions so you have time to prepare the site before the sauna arrives .

❓ Question 5: What is included in the concept of “turnkey”?

📊 Short answer: You receive a fully functional object, ready for utility connections.

✅ Complete turnkey package for a 7×2.7 m sauna :

🏗️ Construction:

• Frame made of pine timber 100×50 mm, treated with bioprotection
• External cladding: thermo-melted imitation timber 22 mm (planken)
• Insulation: 100 mm mineral wool + vapor barrier
• Roofing materials: single-pitched corrugated sheeting, color "Anthracite"

🪵 Interior decoration:

• Steam bath: linden lining (hypoallergenic, does not burn).
• Bath/shower: imitation 22 mm timber.
• Shelves: support-free "floating" made of thermally modified wood.

🔥 Heating and fire protection:

• Novaslav Panorama PKS 02K C3 wood-burning stove
• Stainless steel chimney + Master Flash + ceiling trim
• Fire protection: magnesite + stainless steel screen 1100°C
• Ventilation valves F-100 (alder)

⚡ Electricity:

• Full wiring (VVGng-LS, IP54)
• Panel with circuit breakers and 30 mA RCD
• Sockets, switches, track lights
• LED shelf lighting, paired lamps
• Pipe heating (freeze protection)

🚿 Plumbing:

• Water and sewer pipe installation
• Outputs for sink, shower, boiler
• Steam room trap, cement particle board under tiles (tiles are supplied by the customer)

🚪 Windows and doors:

• Entrance door: metal-plastic, "Anthracite", 2000×860 mm
• Steam room door: Tesli RS for sauna, 1900×700 mm
• Panoramic windows: 2 pcs., 1500×1900 mm, tempered glass 8 mm
• Windows with transom: 2 pcs., 1500×400 mm, for ventilation

🎨 Coverage:

• Exterior: 2 layers of Vidaron V07 "California Redwood", matte
• Inside: clear varnish (walls, ceiling, floor)

❌ What is NOT included in the turnkey package (purchased separately by the Customer):

• Tiles for steam rooms and showers
• Plumbing equipment (sink, shower, boiler)
• Stones for the stove
• Accessories (brooms, buckets, thermometer)

💡 Expert advice : Thermowood's turnkey solution is 95% complete. You save time on construction but control the final design by choosing the tiles and accessories.

❓ Question 6: Can I use the sauna immediately after unloading?

📊 Short answer: Yes, the sauna is ready for the first fire on the day of installation.

🔬 Why is this possible:

• ✅ Factory drying : All materials have a moisture content of 3-12% before assembly
• ✅ Factory assembled : The structure is assembled in a controlled workshop environment, not on an open site
• ✅ Ready infrastructure : Electricity, plumbing, fire protection are already installed and tested

📋 What you need to do before first use:

1️⃣ Connect external communications:

• Electricity: connect the cable to the sauna panel
• Water: Connect to the outlets in the shower
• Sewer: connect to the drain

2️⃣ Check the systems:

• Electricity: RCD test, lighting check
• Plumbing: Leak test, water pressure
• Stove: Checking draft and chimney tightness

3️⃣ First ignition (running-in):

• Heat the oven at minimum power for 30–40 minutes.
• Check if there is smoke in the room
• Check the heating of the shelves and walls

4️⃣ You can steam! 🎉

⚠️ Important : The first ignition should be a "break-in" operation, not at maximum power. This will allow any residual moisture to completely dry out and check all systems.

❓ Question 7: How does delivery and unloading take place?

📊 Short answer: Delivery by special transport, unloading by crane in 30–60 minutes.

🚛 Delivery stages:

1️⃣ Preparation for shipment (1 day):

• Final quality check
• Packaging: corner protection, stretch film, labeling
• Preparation of accompanying documents

2️⃣ Delivery (1–3 days in Ukraine, 5–10 days in the EU):

• Special transport: platform with cargo mounts
• Full value cargo insurance
• Manager support: you get real-time tracking

3️⃣ Arrival at the site:

• Coordination of arrival time 24 hours in advance
• Checking the site's readiness
• Signing of the acceptance certificate

🏗️ Unloading and installation:

💰 Estimated cost of logistics:

💡 Expert advice : Order a crane in advance (2-3 days) to avoid vehicle downtime and additional costs. We can recommend trusted companies in your area.

❓ Question 8: Do you provide a guarantee?

📊 Short answer: Yes, the official factory warranty is 5 years for the structure, 2 years for the equipment.

📋 Warranty details:

✅ 5-year warranty covering (construction):

• Deformation of the frame (distortions, cracks in the timber)
• Rotting or damage to thermally modified wood (if used correctly)
• Differences in seams, breach of tightness
• Assembly defects (factory defects)

✅ 2-year warranty (hardware):

• Stove and chimney components
• Electrical equipment (lighting fixtures, sockets, switchboard)
• Door and window fittings
• Ventilation valves

❌ What the warranty does NOT cover:

• Damage due to improper operation (burning of the stove, flooding)
• Mechanical damage from external factors (impact, falling trees)
• Consequences of lack of basic maintenance (e.g. standing water on the roof)
• Design modifications made by third parties without approval

🔄 How to use the guarantee:

1. Fix the problem:

• Take a photo/video of the defect
• Describe the circumstances of its appearance (when, under what conditions)

1. Contact us:

• Phone / WhatsApp / Viber: +38 067 201 50 50
• Email: info@thermowood-production.de
• Please indicate the contract number and purchase date.

1. Get a decision within 48 hours:

• Online engineer consultation
• On-site visit by a specialist (if necessary)
• Free defect repair or component replacement

🛡️ Expert advice : Keep the contract, acceptance certificate, and warranty card in one place. Take a photo of the sauna immediately after installation—this will help in case of any warranty claims.

🎯 3 more questions that are often unanswered, but worth knowing

❓ Is it possible to install a sauna in winter?

Yes . The structure is designed for operation in temperatures from -30°C to +40°C. Installation is possible at any time of year, provided the site is prepared (free of snow and ice at the support points).

❓ What should I do if my neighbors complain?

1. Calmly explain that this is a temporary structure that does not require a building permit.
2. Please provide the technical data sheet and a link to the State Building Norms (DBN)
3. Make sure that the recommended distances are observed (≥1 m to the fence, ≥3 m to houses)
4. Suggest a compromise: change the location of the chimney, add a screen, etc.

❓ Is it possible to rent out a sauna for business?

Yes . The modular sauna is ideal for green tourism. The payback period for a 20-day/month occupancy rate is 6–10 months . We provide consultations on sole proprietorship registration and fire safety for commercial use.

📞 Any more questions? We're here to help!

• 🔹 Phone / WhatsApp / Viber : +38 067 201 50 50
• 🔹 Email : info@thermowood-production.de
• 🔹 Website : lestorg.org.ua | thermowood-production.de

• ✅ A personal response from an engineer or lawyer within 15 minutes
• ✅ Free consultation on equipment selection
• ✅ Technical data sheet and quality certificates