Fireproofing Detached Structures: Sheds, ADUs, and Garages
When we talk about defending our homes from wildfire, we often focus on the main house—but detached structures like sheds, garages, and ADUs can be just as critical. These secondary buildings can become ignition sources during a wildfire and may even spread fire to your primary home if they’re not protected.
For California homeowners—especially in high-risk fire zones like Orinda, Lafayette, Moraga, and the Oakland Hills—fireproofing these outbuildings should be part of your wildfire defense strategy.
When we talk about defending our homes from wildfire, we often focus on the main house—but detached structures like sheds, garages, and ADUs can be just as critical. These secondary buildings can become ignition sources during a wildfire and may even spread fire to your primary home if they’re not protected.
For California homeowners—especially in high-risk fire zones like Orinda, Lafayette, Moraga, and the Oakland Hills—fireproofing these outbuildings should be part of your wildfire defense strategy.
Why Detached Structures Are at Risk
Detached structures often:
Sit closer to vegetation or property lines
Are built with less fire-resistant materials
Lack proper ventilation or ember protection
Contain flammable contents (tools, gasoline, propane, etc.)
In high heat and wind, these smaller buildings can catch fire quickly and spread flames toward your main home, especially if they're within 30 feet.
The University of California’s Fire Network and Fire Safe Marin both recommend treating detached structures with the same level of fire-hardening as your house.
What Counts as a “Detached Structure”?
Here’s a quick list of structures to consider fireproofing:
Accessory Dwelling Units (ADUs)
Garages and workshops
Sheds (metal or wood)
Pool houses and cabanas
Barns and small storage buildings
Detached offices or studios
If it’s a building you care about—or one that sits near your home—it needs attention.
Step 1: Clean and Clear Zone Zero
Just like your home, the first five feet around detached buildings matter most. Remove:
Firewood, mulch, and debris
Plastic planters and storage bins
Gasoline, propane, or lawn equipment
Any flammable clutter under decks or overhangs
Replace combustible ground cover with gravel, decomposed granite, or pavers. This alone can significantly reduce the risk of ignition from embers.
Step 2: Upgrade Siding and Roofing Materials
Many sheds and garages are built with budget materials like T1-11 plywood or vinyl siding. These can ignite easily when exposed to embers or radiant heat.
Instead, use:
Fiber cement siding or three-coat stucco for siding upgrades
Metal or Class A-rated composition roofing
Boxed-in eaves with ember-resistant soffit vents
Metal trim around windows and doors to reduce heat transfer
Pro tip: Don’t forget the roof. Roofs with accumulated debris are a top cause of ignition.
Step 3: Protect Vents, Doors, and Windows
Detached structures still need airflow—but standard vents are vulnerable. Install:
Ember-resistant vents (1/8” screening or intumescent designs)
Dual-pane tempered glass windows (or no windows at all)
Solid-core or metal doors with tight-fitting seals
Weatherstripping and door sweeps are especially important for ADUs that serve as living spaces.
Step 4: Remove or Relocate Combustible Items
Detached buildings often house the very items that make fires worse:
Lawn mowers, weed whackers, and power tools with fuel
Paint, aerosols, or cleaning chemicals
Propane tanks or spare gas cans
Either:
Move these items to a fire-rated storage locker
Store them in metal cabinets with fire-rated doors
Keep combustibles at least 30 feet from other structures, where possible
Step 5: Fireproof ADUs Like the Main Home
ADUs are often overlooked—but they’re growing in popularity across California. If your ADU is within 30 feet of your home, you should:
Use noncombustible siding and roofing
Box and seal eaves
Install metal or fiberglass doors
Use tempered glass for all windows and skylights
Replace vinyl trim and gutters with metal
Berkeley’s Fire Prevention Inspection Guide treats ADUs as extensions of the primary structure for fire hardening.
Step 6: Full-Structure Fire Shielding for Detached Units
Some structures are too close, too old, or too hard to retrofit. That’s where passive fire shielding comes in.
Fire-resistant blanket systems can:
Fully cover a shed, ADU, or garage
Shield siding, roof, vents, and windows from embers and radiant heat
Be deployed in less than an hour by trained crews
Protect up to 3,000°F without water, power, or supervision
For homeowners with classic backyard studios or converted garages that can’t be rebuilt, this can be a game-changer.
What Fire Inspectors Are Looking For
Fire agencies across Contra Costa and Alameda County will assess:
The distance between your home and detached structures
The condition of the exterior (peeling paint, cracked siding, exposed vents)
The contents inside (fuel, paint, chemicals)
The ground cover around the structure
During fire season, inspectors may recommend or require removal of vegetation and relocation of flammable storage.
Extra Tips for Backyard Buildings
Install metal mesh around decks or crawlspaces to keep embers out
Use metal storage sheds over plastic or wood
Anchor small sheds properly, so they don’t shift during high winds or earthquake retrofitting
Label hazardous materials clearly for fire crews
Use external lighting rated for heat exposure
Final Word
Detached structures deserve the same level of care and planning as your main home. Whether it’s your garage, garden shed, or a new ADU rental, protecting it with defensible space and smart building materials can stop a small spark from becoming a total loss.
And when you can’t afford to retrofit—or just want a backup plan—fire tenting and blanket shielding can offer the peace of mind your property deserves.
The Zone Zero Fire Shield team hopes you find this information helpful.
See also: [Understanding Zone 0] [Creating a Fire-Safe Perimeter] [Best Fire-Resistant Building Materials for Zone 0 and Zone 1]
Top 10 Materials to Avoid in Wildfire Zones
When preparing your home for a wildfire, one of the most important steps is selecting the right building materials. Unfortunately, not all materials are created equal, and some can increase the vulnerability of your home during a wildfire. This blog will outline the top 10 materials to avoid in wildfire zones, helping you make informed choices when protecting your home.
When preparing your home for a wildfire, one of the most important steps is selecting the right building materials. Unfortunately, not all materials are created equal, and some can increase the vulnerability of your home during a wildfire. This blog will outline the top 10 materials to avoid in wildfire zones, helping you make informed choices when protecting your home.
Why Material Selection Matters in Wildfire Defense
The materials you choose for your home’s roof, siding, deck, and landscaping play a huge role in how well it can withstand the extreme conditions of a wildfire. Wildfires are unpredictable, and ember attacks, radiant heat, and direct flames are just a few of the risks to consider. Certain materials are highly flammable, which can contribute to the rapid spread of fire, putting your property—and potentially the whole neighborhood—at greater risk.
Let's explore the top 10 materials you should avoid when building or renovating your home in a wildfire zone.
1. Wood Shingles/Shakes
Wood shingles and shakes are classic roofing materials, but they are also one of the most flammable options. During a wildfire, embers can easily ignite wooden shingles, causing the fire to spread quickly. Even if a fire doesn’t directly touch the roof, the heat from nearby flames can still ignite wood shingles.
Recommendation: Opt for Class A fire-rated roofing materials like metal, clay tiles, or composite shingles.
2. Unrated Asphalt Shingles
Asphalt shingles are commonly used due to their cost-effectiveness, but they don’t provide adequate protection in a wildfire. Unrated asphalt shingles are particularly vulnerable to the heat and embers produced by wildfires, making them an unsafe choice for homes in fire-prone areas.
Recommendation: Choose Class A fire-rated composite shingles or metal roofing for better fire protection.
3. Vinyl Siding
Vinyl siding is an affordable option, but it is highly flammable and can melt or catch fire when exposed to heat. The melting vinyl can spread flames to your home’s interior, further damaging your property. It’s important to avoid vinyl siding, especially in Zone 0 and Zone 1.
Recommendation: Go for fiber cement board or metal siding, both of which are fire-resistant options.
4. Treated Wood (Untreated)
While treated wood can offer some level of protection against moisture and pests, it is still highly flammable and should be avoided in high-risk wildfire zones. When untreated, wood is even more susceptible to fire, and it can act as fuel during a wildfire, spreading flames rapidly.
Recommendation: Use fire-resistant materials like fiber cement board or fire-rated wood products.
5. Plastic or PVC Gutters
Plastic gutters may seem like a cost-effective solution, but they melt quickly and can easily catch fire when embers land on them. Plastic is one of the most flammable materials around your home, and it’s best to avoid it in favor of more fire-resistant options.
Recommendation: Install galvanized steel or aluminum gutters with metal gutter guards to prevent ember buildup.
6. Synthetic Turf
Synthetic turf might look appealing, but it is a non-natural material that can melt and catch fire quickly. The plastics and chemicals used in synthetic turf make it a significant fire hazard when exposed to intense heat.
Recommendation: Use natural, fire-resistant ground covers like succulents, grass, or wildflower meadows to maintain aesthetic appeal without compromising safety.
7. Plastic Window Frames
Plastic window frames, while lightweight and inexpensive, are highly flammable. When exposed to the intense heat of a wildfire, plastic window frames can melt or ignite, allowing embers to easily enter your home.
Recommendation: Choose metal or aluminum window frames that provide better protection from both heat and flames.
8. Wood Decking
Wooden decks are one of the most vulnerable areas of a home during a wildfire, as embers can easily settle underneath and ignite the wood. The flame can spread quickly, causing significant damage to your property and posing a risk to your entire structure.
Recommendation: Opt for fire-rated composite decking or metal decking to prevent fire spread from beneath the deck.
9. Traditional Wood Fencing
Wooden fences attached to your home can act as a bridge for fire to spread to your structure. The flammable nature of wood, combined with its ability to easily ignite from embers, makes traditional wood fencing a poor choice for wildfire defense.
Recommendation: Install metal, stone, or masonry fencing to create a fire-resistant barrier around your home.
10. Highly Flammable Mulch
Mulch is often used in landscaping but can be a major fire hazard, especially when it is made of wood chips or bark. These materials are highly flammable, and dry conditions can make them catch fire even more easily.
Recommendation: Replace wood mulch with gravel, stone, or decomposed granite. These non-combustible materials provide a beautiful, fire-safe landscaping solution.
Bonus: Full-Structure Fire Shielding
Even with the best materials in place, there are scenarios—like a neighboring home catching fire—where radiant heat and ember storms may overwhelm your defenses. That’s where full-structure fire shielding comes in.
Our solution is:
Waterless (no plumbing or sprinkler system needed)
Self-sufficient (no supervision required)
Rated to 3,000°F, with deployment designed to protect against ember storms and radiant heat
Final Thought:
While it’s important to use fire-resistant materials for every part of your home, it’s equally important to think about Zone 0 and Zone 1 when designing and landscaping your property. By avoiding highly flammable materials and focusing on non-combustible options, you can help ensure that your home is better protected from the dangers of wildfire.
The Zone Zero Fire Shield team hopes you find this information helpful.