When it comes to choosing materials that can withstand high heat, wood might not seem like the most obvious choice. However, certain types of wood are naturally more heat-resistant due to their density, moisture content, and resin levels. For applications like fireplace mantels, sauna materials, and outdoor furnishing, heat-resistant woods can be an attractive, durable, and safer option.
This comprehensive guide will explore the key traits that make woods heat-resistant, identify the best high-heat woods, and provide tips for treating and working with woods to enhance their heat protection. Read on for expert insight into selecting and using the most flame-retardant woods for your next project.
How Wood Density and Composition Impact Heat Resistance
The main factors that influence a wood‘s capacity to resist heat and fire include:
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Density – Denser woods with tighter grain patterns tend to be more resistant. Density makes woods harder to ignite.
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Moisture – Wet woods are harder to burn. Dry woods catch fire quicker. Proper drying is key.
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Oils & Resins – Woods with natural oils and resins tend to be more flammable. Low resin woods burn slower.
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Chemical Treatment – Adding fire retardant coatings enhances heat protection.
Understanding these key traits will help you choose woods that are naturally more heat-resistant for fireplace surrounds, chimney chases, sauna benches, and other high-heat uses.
The Top 7 Most Heat Resistant Wood Types
1. Lignum Vitae
- Extremely dense, rated 4500 lbf on Janka scale
- Contains oils that retard burning
- Nicknamed "ironwood" for hardness
- Popular for mallet heads, bearings, boats
2. Ebony
- One of the densest woods globally
- Very high mineral content
- Slow to ignite and burn
- Used for musical instruments, fine furniture
3. Teak
- Naturally high oil content
- Resists both rot and fire
- Ideal for boat decking, outdoor furniture
- Requires no chemical treatment
4. Ipe
- Up to 3x harder than oak
- Very high fire resistance
- Common for decks, siding, outdoor uses
- Can last 40+ years outdoors
5. Ironwood
- Extremely dense, durable wood
- Term used for many woods like Desert Ironwood
- Rot and insect resistant
- Popular for outdoor applications
6. White Oak
- Very hard, dense wood
- Ideal for fireplace mantels, facing
- Can be treated for even better heat protection
- A commonly available domestic wood
7. Redwood
- Contains natural fire retardant oils
- More resistant than softwoods like pine
- Great choice for saunas, hot tub surrounds
- Lightweight yet very durable
This list provides a overview of some exceptional woods in terms of natural heat and fire resistance. Many can be further enhanced with additives.
Enhancing Regular Woods with Fire Retardant Treatments
While some woods have natural heat resistance, almost any wood can have its fire retardant properties improved through treatments. Here are some options:
Fire Retardant Paints & Varnishes
- Can be used on installed wood surfaces
- Provides topical coating against heat and flame
- Multiple coats maximize protection
Pressure Treating
- Fire retardant chemicals forced deeply into wood
- Done at lumber manufacturing level
- Makes wood fire, rot, and insect resistant
Intumescents
- Fireretardant coatings that swell when heated
- Useful for maintaining attractive wood look
- Popular for architectural millwork
Always check treatment manufacturer guidelines carefully and test on scrap pieces first. Take safety precautions when applying chemical wood treatments.
Proper installation and maintenance are also key for any fire retardant wood. Ensure good airflow in spaces and reapply coatings as needed.
What is Fireproof Wood?
You may come across the term "fireproof wood" which refers to woods treated to have a fire resistance rating of up to 2 hours. This wood has undergone a standardized pressure impregnation process with fire retardant chemicals.
Some common examples include:
- FirePro Wood
- Hoover Treated Wood Products
- FlameFree Wood
- Safe Lumber
Look for stamps from rating agencies like Underwriters Laboratories. This type of fireproof lumber is used when code requires enhanced fire resistance, such as:
- Commercial buildings
- Multi-family homes
- Elevated decks
While not 100% fireproof, these woods will not ignite as easily and slow the spread of flames, reducing structural damage.
The Limitations of MDF Around Heat Sources
MDF (medium density fiberboard) is an engineered wood popular for interior uses like cabinets, trim, and furniture. However, MDF has some limitations when it comes to heat resistance:
- The resins can burn, causing flaming and smoking
- Easily warped by excess moisture and steam
- No natural fire retardant oils like wood
- Low maximum temperature tolerance
MDF products are available with fire retardant additives added but have lower heat tolerance than solid wood. Use caution around heaters, stoves, candles or other ignition sources. Consider alternative materials like stone, metal and tile for very high heat areas.
What Types of Wood Won‘t Burn?
While all woods will burn given the right conditions, some are far more difficult to ignite owing to their density, resin content, and moisture levels. Here are some of the least flammable woods:
- Teak – Very dense grain and natural oils
- Ebony – Extremely dense with mineral deposits
- Eastern Red Cedar – High moisture content
- White Oak – Very tight, dense grain
Even these woods can be encouraged to burn with kindling when dried. But under normal circumstances, they resist burning and smoldering naturally.
Woods that may seem impossible to burn when wet or green can still ignite when seasoned. Even still, the most challenging woods to successfully burn are those most resistant mentioned above.
Which Wood Burns the Longest in a Fireplace?
For a long-lasting fireplace fire, the best woods are those with high density that burn slowly and evenly. Here are some top choices:
- Oak – Very hot, dense fire, long-lasting coals
- Maple – Slow burning with good heat output
- Ash – Excellent firewood, burns for 2+ hours
- Beech – Hard wood that provides intense heat
Conversely, soft resinous woods like pine, spruce and larch burn very quickly and intensely. They are better for kindling. The exact burn time depends on moisture content, draft, and flame space. But choosing dense, dry hardwoods is key for the most enduring heat.
Is Plywood Heat Resistant? Tips for Use Around Heat
Basic plywood is not designed to withstand high heat levels. However:
- Fire retardant treated plywoods are available
- Some finishes offer limited heat protection
- Proper sealing protects from moisture damage
Avoid direct heat contact on plywood. For applications like wood stoves, use specialized cement boards or similar materials. When sealing, take care not to trap moisture against the wood.
While plywood can‘t endure extreme heat, sealing and prudent design can allow sensible use around moderate heat sources. Take precautions and test materials before prolonged use.
How Hot Can Unfinished Wood Get Before Igniting?
Unfinished, bone-dry wood generally ignites between 400-500°F. However, multiple factors impact exact ignition temperature:
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Wood Type – Dense hardwoods are higher; softwoods lower
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Moisture – Wet wood ignites at higher temps
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Oils – Woods with natural oils ignite more readily
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Exposure Time – Prolonged heat impact decreases ignition temperature
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Environment – More oxygen can lower ignition temperature
Under typical conditions, expect unfinished wood to ignite between 300-425°F. Stained or painted wood is slightly more resistant. Monitor wood around any heat source and keep a safety margin well below ignition. Use a thermometer if wood will experience prolonged heat exposure during use.
Identifying Heat Treated Wood
You can identify heat treated wood through these signs:
- Darkened wood grain, especially near cracks
- Dull, dry-looking surface vs untreated wood
- Noticeable brittleness
- Distinct brown wood color visible on end grain
- Small surface splits in end wood
- smell
Minor heat exposure may only darken the surface. More extreme treatment can Embrittle and discolor throughout.
Look for markings, but some manufacturers may not indicate treatment. When uncertain, contact the supplier. It is also smart to seal and finish heat-treated wood to optimize weather resistance.
Is It Safe To Burn Heat Treated Firewood?
Yes, heat-treated firewood is generally safe to burn. The heat treatment process is designed to kill pests and fungi in wood by using only heat and steam, not chemicals.
Examples of heat treated firewood include:
- Kiln Dried Firewood
- Heat Treated Pallet Wood
- Firewood Sold as Pest-Free
This firewood produces no toxic chemicals when burned and does not release preserved materials either. Burning heat treated wood has no additional risks over regular firewood.
However, always follow standard fire safety practices like ensuring proper ventilation and safely extinguishing ashes after use. Heat treatment makes firewood last longer and burn cleaner.
Conclusion
When selecting wood materials for uses around heat sources, considering the wood‘s natural resistance, treatment options, and proper installation practices will ensure optimal safety and performance. While no wood is 100% fireproof, the woods covered in this guide represent excellent choices for fireplace mantels, sauna materials, restaurant interiors, and other applications demanding heat resistance.
Do your homework when sourcing wood for any high heat uses. Seek out responsible suppliers of sustainable, specialized heat resistant woods. And always incorporate redundant protections like screens and monitors when wood will experience prolonged heat exposure in service. With prudence and common sense, wood can provide beauty and functionality even in hot environments.
