When it comes to using timber in construction or interiors, fire safety is a key consideration. Wood is a combustible material, but with the right treatment or selection, it can be made far safer in the event of a fire.
That’s where the terms fire retardant and fire resistant come into play. They’re often used interchangeably, but they refer to two different concepts, and choosing the wrong type of timber for your project could result in non-compliance or increased risk.
So, what exactly is the difference between fire-retardant and fire-resistant wood, and how do these materials behave under fire conditions?
Let’s break it down.
The Short Answer
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Fire-retardant wood is timber that has been treated with chemicals to slow the spread of fire.
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Fire-resistant wood refers to timber (treated or naturally dense) that resists ignition or maintains its structural integrity longer under heat.
In most cases, fire retardant = slows fire, and fire resistant = survives fire.
What Is Fire Retardant Wood?
Fire-retardant wood has undergone a surface or pressure treatment that reduces how quickly it burns or spreads flames.
These treatments typically involve:
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Surface coatings like fire-retardant paint or varnish
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Pressure impregnation, where chemicals penetrate the timber fibres
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Intumescent coatings, which swell to form a protective char when exposed to heat
How It Works:
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Slows down ignition
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Reduces flame spread
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Minimises smoke production
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Often self-extinguishes once the flame source is removed
Where It’s Used:
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Interior cladding, panelling, and ceilings
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Timber in public or commercial buildings (to meet fire regulations)
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Garden structures and sheds (when near buildings or boundaries)
Tested To:
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EN 13501-1 or BS 476 Part 7
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Common classifications: Euroclass B or C (B-s1,d0 is best for smoke control)
What Is Fire-Resistant Wood?
Fire-resistant wood is timber that withstands fire exposure without losing its structural integrity too quickly. This may be due to natural properties (like density) or added treatments.
The focus here is not just on slowing the fire but on maintaining load-bearing performance during fire exposure, which is essential for structural timber.
How It Works:
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Resists ignition or charring
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Maintains strength and stiffness under high temperatures
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Slows the rate of failure or collapse
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May also include encapsulated timber systems with fireboards
Where It’s Used:
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Structural elements in timber frame buildings
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Mass timber (e.g. CLT, glulam) construction
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Fire-rated walls, floors, and ceilings in multi-storey buildings
Tested To:
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EN 1365 (fire resistance of load-bearing elements)
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BS EN 1995-1-2 (Eurocode 5 – structural fire design)
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Fire resistance classes: 30, 60, 90, or 120 minutes
Key Differences at a Glance
| Feature | Fire Retardant Wood | Fire-Resistant Wood |
|---|---|---|
| Main Purpose | Delay ignition and reduce flame spread | Maintain strength during fire exposure |
| Treatment Type | Surface coating or pressure impregnation | May be natural (dense) or treated |
| Common Use | Decorative or cladding applications | Structural or load-bearing timber |
| Reaction to Fire | Slows fire progression | Resists structural failure |
| Test Standard | EN 13501-1 / BS 476 | EN 1365 / BS EN 1995 |
| Fire Rating Focus | Flame spread, smoke development | Time-based resistance (30–120 minutes) |
Are Any Woods Naturally Fire-Resistant?
Yes, some timber species have better natural resistance due to their density, moisture content, and structure. Examples include:
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Teak
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Ipe
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Mahogany
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Western Red Cedar (moderate resistance)
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Douglas Fir (often used with fire-resistant design strategies)
However, natural fire resistance is usually not enough to meet UK building regulations unless enhanced by treatment or design.
Can You Use Fire Retardant Wood for Structural Elements?
No, not typically.
Fire retardant treatments are not designed to maintain structural performance under fire conditions. While they may protect the timber from surface flame spread, the core strength can still degrade quickly in high heat.
Structural elements should either:
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Be oversized to allow for predictable charring, or
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Be protected by fire-resistant cladding or boards
Final Thoughts
Understanding the difference between fire-retardant and fire-resistant wood is vital for choosing the right material for your project and ensuring full compliance with fire safety regulations.
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Use fire-retardant wood for non-structural components like cladding, panelling, or decorative finishes, especially in escape routes or public areas.
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Choose fire-resistant systems or fire-protected timber when the wood plays a load-bearing or structural role.
In both cases, make sure the product is certified, tested to the correct standard, and installed according to manufacturer guidelines.
For expert advice on fire protection and prevention measures, contact Martyn Young Fireproofing Consultancy on 07585 896648