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.

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]

How to Harden Your Home for Ember Resistance

In the wildfire-prone regions of Alameda and Contra Costa Counties, California, protecting your home from ember attacks is crucial. Embers—small, windborne burning particles—are responsible for igniting the majority of homes during wildfires. As climate change intensifies fire seasons, hardening your home against these embers is more important than ever. This blog will explore the best methods and materials for hardening your home against ember attacks and radiant heat.

Understanding Ember Resistance

Ember resistance involves making your home less susceptible to ignition from flying embers. This includes sealing gaps, using fire-resistant materials, and creating defensible space. Local fire agencies, such as the Contra Costa County Fire Protection District, emphasize that "home hardening includes using fire-resistant building materials, adopting safe landscaping practices, and implementing preventative measures to reduce fire risk and enhance property safety" (cccfpd.org).

Key Areas to Harden

1. Roofing

Your roof is a primary target for embers. The Contra Costa County Fire Protection District recommends installing Class A fire-rated roofing materials, such as metal, clay, or concrete tiles, to prevent ignition from flying embers. Avoid using wood shakes or untreated wood shingles, as they are highly combustible.

• Recommendation: Opt for Class A fire-rated materials like metal, clay, or concrete tiles.
  
  

• Avoid: Wood shakes or untreated wood shingles.
  
  

By using these materials, you can significantly reduce the risk of ember ignition on your roof.

2. Vents and Eaves

Embers can enter your home through vents and eaves. The Moraga-Orinda Fire District offers free ember-resistant vent mesh and provides reimbursement for the installation of ember-resistant vents (mofd.org). Additionally, CAL FIRE advises installing 1/16-inch to 1/8-inch noncombustible, corrosion-resistant metal mesh over vents to block embers from entering (readyforwildfire.org).

• Recommendation: Install ember-resistant vents with 1/8-inch mesh and screened soffits.
  
  

• Avoid: Unprotected vents and poorly sealed eaves.
  
  

Sealing these gaps will prevent embers from entering your attic or other cavities, reducing the risk of fire spreading inside your home.

3. Windows

Windows are another vulnerable part of your home. Heat from radiant heat or flying embers can cause windows to crack or shatter, allowing embers to enter your home. To reduce the risk, choose windows that are resistant to high temperatures and flying debris.

• Recommendation: Install dual-pane tempered glass windows, which are stronger and provide better protection against heat and embers.
  
  

• Avoid: Single-pane windows or acrylic windows, which are more likely to shatter or melt under high heat.
  
  

Tempered glass windows will not only withstand higher temperatures but also prevent embers from entering your home if the glass is exposed to radiant heat.

4. Siding and Decking

Combustible siding and decking materials can catch fire from embers. The East Bay Wildfire Coalition of Governments advises using fire-resistant materials like fiber cement or metal for siding and decking to reduce the risk of ignition (eastbaywildfire.org).

• Recommendation: Use fiber cement board or metal for siding, and fire-rated composite decking or metal grating for decks.
  
  

• Avoid: Vinyl siding, untreated wood, and wood decking.
  
  

These materials are less likely to catch fire from airborne embers, helping to protect your home from the initial spark that could lead to a larger blaze.

5. Gutters

Debris-filled gutters can ignite from embers. The Moraga-Orinda Fire District recommends installing metal gutter guards to prevent debris accumulation and reduce fire risk (mofd.org).

• Recommendation: Install metal gutters with gutter guards to keep debris from collecting.
  
  

• Avoid: Plastic or vinyl gutters, which are easily ignited.
  
  

Regularly cleaning gutters and installing metal gutter guards will ensure that debris doesn’t become fuel for a potential fire.

6. Decking: Wildfire-Rated or Noncombustible

Decks are a common point of vulnerability during wildfires, as embers often settle underneath and can ignite the wood. To protect your home, consider fire-rated decking materials.

• Recommendation: Opt for fire-rated composite decking or metal decking to prevent embers from igniting the surface.
  
  

• Avoid: Wooden decking, which can easily catch fire from underneath.
  
  

By choosing non-combustible or fire-rated decking materials, you can create a safer outdoor space that won’t contribute to the spread of fire.

Creating Defensible Space

Defensible space is the buffer you create between your home and the surrounding vegetation. The Contra Costa County Fire Protection District emphasizes that "defensible space, coupled with home hardening, is essential to improve your home’s chance of surviving a wildfire" (cccfpd.org).

Zone 0 (0–5 feet from the home)

This area should be free of combustible materials. The Berkeley FireSafe Council advises removing mulch, leaves, and other flammable materials within this zone to prevent ember ignition (berkeleyfiresafe.org).

• Recommendation: Clear combustible materials such as mulch, leaves, and dry grass from the 0-5 foot zone.
  
  

• Avoid: Any materials that can easily catch fire, such as bark mulch and dry grass.
  
  

A clean, non-combustible zone ensures that embers won’t have a chance to ignite the area immediately surrounding your home.

Zone 1 (5–30 feet from the home)

Maintain a defensible space by clearing dead vegetation and creating horizontal and vertical spacing between trees and shrubs. The East Bay Wildfire Coalition recommends using fire-resistant plants and maintaining defensible space to reduce fire risk (eastbaywildfire.org).

• Recommendation: Remove dead vegetation, space trees and shrubs at least 18 feet apart, and use low-growing fire-resistant plants.
  
  

• Avoid: Planting highly flammable plants, like juniper or pine trees, close to the house.
  
  

This zone serves as a buffer to slow or stop fire from reaching your home. Properly spaced trees and fire-resistant plants will significantly reduce your risk.

Zone 2 (30–100 feet from the home)

This area should be managed to slow or stop the spread of wildfire. The Contra Costa County Fire Protection District advises thinning trees and shrubs to create a defensible space that helps protect your home from catching fire (cccfpd.org).

• Recommendation: Thin trees and large shrubs to maintain spacing and reduce the fuel load.
  
  

• Avoid: Overgrown vegetation and ladder fuels that allow fire to climb to the tree canopy.
  
  

Proper vegetation management in this zone will help slow down a wildfire’s approach and provide a better chance for firefighters to defend your home.

Local Resources and Incentives

Several local agencies offer resources and incentives to assist homeowners in hardening their homes:

• Moraga-Orinda Fire District: Offers a Home Hardening Grant Program that provides reimbursement for the purchase of ember-resistant vents and gutter guards (mofd.org).
  
  

• Berkeley Fire Department: Provides guidelines and resources for home hardening and defensible space through the FireSafe Berkeley initiative (berkeleyfiresafe.org).
  
  

• CAL FIRE: Offers comprehensive information on home hardening and defensible space on their website (fire.ca.gov).
  
  

Conclusion

Hardening your home against ember attacks is a proactive step in safeguarding your property from wildfires. By implementing the recommendations from local fire agencies and utilizing available resources, you can significantly reduce the risk of your home igniting from flying embers. Remember, creating a defensible space and using fire-resistant materials are key components in enhancing your home's resilience to wildfires.

Related Blogs in Our Series:

• Top 10 Materials to Avoid in Wildfire Zones
  
  

• Creating a Fire-Safe Perimeter
  
  

• The Role of Fire-Resistant Landscaping in Wildfire Defense