---
title: "what home hardening does, and where it stops"
canonical_url: https://ensurance.app/guide/what-home-hardening-does-and-where-it-stops
markdown_url: https://ensurance.app/guide/what-home-hardening-does-and-where-it-stops.md
subtitle: "a class A roof, ember-resistant vents and a clear five feet keep embers from finding a way in. how many embers arrive is shaped by the land around the house"
category: how-to
---

# what home hardening does, and where it stops

*a class A roof, ember-resistant vents and a clear five feet keep embers from finding a way in. how many embers arrive is shaped by the land around the house*

**What is home hardening?** Home hardening is the work of making a house hard for wildfire to ignite: a Class A roof, vents screened against embers, noncombustible gutters, a clear five-foot zone around the walls and decks, and tougher glass. It works, so do it. It cannot change how many embers arrive; the land around the house shapes that.

Embers are the leading cause of home ignitions in a wildfire. The house mostly decides whether an ember finds a way in. The forest, the brush and the grass on the slope above the street shape how hot the fire runs and how many embers arrive; wind and burning neighbors add their own.

That fuel shapes the fire that reaches a house whether or not anyone pays for its keeping. [**Ensurance**](/manual/ensurance?from=guide) is how the people who depend on that ground can pay for its keeping. It is not the forest, and it does not harden a roof.

Why insurers call this work mitigation and climate policy calls it adaptation is in [mitigation means two different things](/guide/mitigation-means-two-different-things?from=guide).

## what home hardening asks of a house

The clearest checklist in the field is the Wildfire Prepared Home standard from the Insurance Institute for Business & Home Safety (IBHS). Its December 2025 version took effect June 1, 2026, per the program page. The rows below, all from that standard, are its Base level unless marked Plus, the higher designation.

| part of the house | what the standard asks |
|---|---|
| Roof | A covering with "a Class A rating when tested in accordance with ASTM E108 or UL 790": a fire rating earned in standard tests from ASTM International and UL (formerly Underwriters Laboratories). Kept clear of leaves and needles. Wood shakes and shingles are not allowed at any rating |
| Gutters | Noncombustible material such as metal, kept clear of debris. Covered gutters at the Plus level |
| Vents | Noncombustible, corrosion-resistant mesh "with openings not to exceed 1/8-inch", or vents that pass an ember test (ASTM E2886) |
| Base of the walls | At least 6 inches of noncombustible material from the ground or deck up |
| Zone 0 | Plants and mulch cleared to bare mineral soil, and "all combustible items within 5 feet" of the building and its attachments removed or replaced with noncombustible versions, such as wood fences, firewood and furniture, with listed exceptions |
| Decks | A combustible attached deck counts as part of the building and gets its own five-foot zone, measured from its outer posts. At the Plus level, a noncombustible walking surface and railings near the house |
| Windows | At the Plus level, multipane glass with at least two tempered panes, or fire-rated glass |

For a new home, Headwaters Economics found in 2018 that one built to wildfire-resistant codes "can be constructed for roughly the same cost as a typical home"; its western Montana model came in 2% less. A roof retrofit in the same study came to $22,010. One model house; the retrofit bill falls on owners. Renters cannot make these changes themselves.

## how a house actually catches fire

IBHS calls embers "the leading cause of home ignitions." After the 2017–2018 California wildfires, including the Camp Fire, its damage analysis found embers "account for up to 90 percent of home ignitions."

The same analysis saw "structure-to-structure fire spread" where homes stood close together. Once one house burns, it is fuel for the next. That is the first place hardening runs out of reach: your neighbor's house is part of your fire.

## defensible space is the bridge

**Defensible space** is the cleared, spaced ground between the building and the land. The IBHS standard sets two zones.

The first five feet is the noncombustible zone in the table, which the standard calls "the most critical area of defensible space."

From 5 to 30 feet, vegetation is spaced, limbed and kept short "to slow fire spread and reduce flame intensity near the building." The zone runs to 30 feet "or to the property line, whichever is closest."

The standard stops where the deed stops.

## what the evidence says

The studies point the same way on the structure.

- **Modeled.** A 2020 study by the National Association of Insurance Commissioners' Center for Insurance Policy Research, with the modeling firm RMS (Risk Management Solutions) and IBHS, found "structural modifications can reduce wildfire risk up to 40%, and structural and vegetation modifications combined can reduce wildfire risk up to 75%." Model results for nine communities in California, Colorado and Oregon, against a neutral property; "up to" is the best case.
- **Field, IBHS.** After the Camp Fire, IBHS found "defensible space was an important characteristic of homes that survived," and that mitigation works best when "building design, materials and surrounding defensible space are all addressed."
- **Field, statistical.** Studying the Camp Fire, Troy and colleagues (International Journal of Wildland Fire, 2022) found "structural hardness factors" such as double-paned windows, enclosed eaves and ignition-resistant roofs and siding "are important in determining structure survival." Homes built after California's 2005 and 2007 fire-safe code updates "were more likely to survive," and "mobile homes were far more likely to be destroyed." But "defensible space clearance had only a weak association with structure survival."
- **Payback.** For new buildings built to the 2015 International Wildland-Urban Interface Code, where fire risk is moderate or higher, the National Institute of Building Sciences estimated $4 saved per $1 (2019); retrofits $2, federal grants $3.

Read together: both field studies found the structure mattered. IBHS found clearance important; Troy found "only a weak association" with survival, so its size is still argued. Do both.

## where home hardening stops

How hot a wildfire runs and how many embers it throws depend on the fuel it crosses: how dense the forest is, how much dead material lies on the ground. That fuel sits on public land, private land and the lot next door. No homeowner controls it alone.

A hardened house raises the bar an ember has to clear. The land shapes how many embers try, and wind and burning houses add more. A house built to every row of the table can still burn when the ember load is high enough or the house next door goes up.

## what the land around the house can do

A 2021 review of western North American forests by Prichard and colleagues found that "across a wide range of sites, thin and prescribed burn treatments are most effective at reducing fire severity," while "thinning alone achieves a reduction of canopy fuels but contributes to higher surface fuel loads."

Two limits. The finding is about fire severity in forest stands; it does not show that treatment reduces home losses. And no treatment stops every fire. Fuel builds back over time, so the work has to be kept up, year after year. The landscape view of wildfire is in [the spark gets the blame](/guide/the-spark-gets-the-blame?from=guide).

## who recognizes hardening today

California's "Safer from Wildfires" regulation, filed and operative on October 14, 2022, says "[n]o insurer shall use a rating plan that does not take into account and reflect" a list of mandatory factors. On the property they include a Class A roof, enclosed eaves, fire-resistant vents, multipane windows or shutters, and clearing within 5 feet. The rule also names community-level factors: a Firewise USA site and a Fire Risk Reduction Community. Even the rating rule reaches past the lot.

A 2024 draft primer from the National Association of Insurance Commissioners adds that catastrophe models "use distinct characteristics representing building hardening features to reflect lower damage". What discounts exist and what they are worth is in [does mitigation lower insurance premiums?](/guide/does-mitigation-lower-insurance-premiums?from=guide) and [share the premium saving with the land](/guide/share-the-premium-saving-with-the-land?from=guide). If your policy is already at risk, start with [wildfire insurance non-renewal](/guide/wildfire-insurance-non-renewal?from=guide).

:::johnson
**the house can be ready. the embers come from the land.**

Harden the roof, the vents, the gutters, the glass and the first five feet. The slope above the street shapes how many embers come. Ask who keeps it.

[see the wildfire resilience account →](/wildfire-resilience.syndicate?from=guide)
:::

## the two halves for a wildfire neighborhood

| half | the work | where it happens | who decides |
|---|---|---|---|
| The house | Roof, gutters, vents, wall base, decks, glass | On the building | The owner |
| The lot | The five-foot zone and the 5 to 30 feet beyond it | Up to the property line | The owner, and neighbors where lots meet |
| The land | Thinning, prescribed fire and the upkeep after | The slope, the forest and the open ground between lots | Land managers, agencies and neighbors together, if anyone |

The first two rows have a standard. The third row can lower the fire for every house at once, so no single policyholder owns it or pays for it.

## what ensurance does, and what it does not

Ensurance does not harden a roof, inspect a house or set a premium. No premium has been lowered by ensurance.

It is designed to give the third row a way to be paid for, and it is early in the build. A place can hold an **account** in its own name, the forest or slope it depends on can be named in a **certificate**, and payments from the people who depend on that ground are designed to go as **proceeds** to the people who keep it. [Wildfire resilience](/wildfire-resilience.syndicate?from=guide) is a live account that coordinates wildfire mitigation and forest health across fire-prone communities. [Risk Resilience](/risk-resilience.ensurance?from=guide) is the wider door.

To see what your place loses to wildfire in an average year, by the Federal Emergency Management Agency's (FEMA) expected annual loss, [look up your place](/place?from=guide). If you hold land on the slope, see [ensurance for landowners](/solutions/landowners?from=guide&topic=mitigation-and-adaptation). The full peril-by-peril map is in [every mitigation strategy has two halves](/guide/every-mitigation-strategy-has-two-halves?from=guide).

## frequently asked questions

### what is home hardening?

Changing a house so embers and flames find nothing to ignite: a Class A roof, ember-resistant vents, noncombustible gutters and wall base, protected decks and glass, and a clear first five feet.

### does home hardening lower insurance premiums?

Sometimes. California has required insurers' rating plans to reflect named hardening features since 2022. See [does mitigation lower insurance premiums?](/guide/does-mitigation-lower-insurance-premiums?from=guide).

### is defensible space part of home hardening?

They work as a pair: the building, and the ground around it to 30 feet or the property line. IBHS found both mattered at the Camp Fire; a 2022 study found "only a weak association" between clearance and survival.

### can a hardened house still burn?

Yes. A heavy ember load or a burning house next door can overwhelm any checklist. Hardening lowers the odds; the fuel across the landscape shapes how hard the test is.

This post is general information, not insurance, engineering, legal or tax advice.

## sources

[IBHS, Wildfire Prepared Home Technical Standard (December 2025)](https://wildfireprepared.org/wp-content/uploads/WFPH-Technical-Standard-12-25.pdf) — Class A roof, gutters, 1/8-inch vent mesh, 6-inch wall base, decks, Plus-level glass, the 0–5 foot zone and the 5–30 foot zone to the property line

[IBHS, Wildfire Prepared Home program page](https://wildfireprepared.org/home-technical-standard/) — Embers as "the leading cause of home ignitions"; effective date June 1, 2026

[IBHS, damage analysis of the 2017–2018 wildfires (July 13, 2020)](https://ibhs.org/ibhs-news-releases/damage-analysis-of-2017-2018-wildfires-shows-importance-of-mitigation/) — Embers "up to 90 percent of home ignitions", defensible space at the Camp Fire, structure-to-structure spread

[NAIC Center for Insurance Policy Research, RMS and IBHS, Application of Wildfire Mitigation to Insured Property Exposure (November 2020)](https://content.naic.org/sites/default/files/cipr_report_wildfire_mitigation_0.pdf) — Modeled risk reduction up to 40% (structure) and up to 75% (structure and vegetation), nine communities

[Troy et al., International Journal of Wildland Fire 31(6) (2022)](https://connectsci.au/wf/article/31/6/586/21844/An-analysis-of-factors-influencing-structure-loss) — Camp Fire structure survival: hardness factors and newer codes mattered, mobile homes far more likely destroyed; defensible space "only a weak association"

[Headwaters Economics, Building a Wildfire-Resistant Home: Codes and Costs (2018)](https://headwaterseconomics.org/natural-hazards/building-costs-codes/) — New wildfire-resistant home at roughly the same cost (model home 2% less); roof retrofit $22,010

[National Institute of Building Sciences, Natural Hazard Mitigation Saves 2019, fact sheet](https://nibs.org/wp-content/uploads/2025/04/ms_v3_exceeds_iwuic.pdf) — Wildland-urban interface fire: complying with the 2015 International Wildland-Urban Interface Code returns $4 per $1 for new buildings where fire risk is moderate or higher; retrofit 2:1, federal grants 3:1

[California Code of Regulations, title 10, § 2644.9 (Cornell LII)](https://www.law.cornell.edu/regulations/california/10-CCR-2644.9) — Mandatory wildfire mitigation rating factors, filed and operative October 14, 2022

[Prichard et al., Ecological Applications 31(8): e02433 (2021)](https://escholarship.org/content/qt1w52p1dp/qt1w52p1dp.pdf) — Thinning with prescribed burning most effective at reducing fire severity; thinning alone raises surface fuels

[NAIC, Catastrophe Modeling Primer, exposure draft (December 2024)](https://content.naic.org/sites/default/files/inline-files/10_23_24%20Exposure%20Draft%20of%20Cat%20Modeling%20Primer.pdf) — Models use building hardening features to reflect lower damage

## the series

1. [mitigation means two different things](/guide/mitigation-means-two-different-things?from=guide) — **Read first:** In climate policy, mitigation cuts emissions and adaptation cuts the damage; in insurance, mitigation is the adaptation
2. [hazard, exposure, vulnerability](/guide/hazard-exposure-vulnerability?from=guide) — The three things a loss is made of, and which one each kind of mitigation moves
3. [what home hardening does, and where it stops](/guide/what-home-hardening-does-and-where-it-stops?from=guide) — A ready house keeps embers out; how many arrive is shaped by the land around it
4. [flood proofing raises the house. the floodplain lowers the water](/guide/flood-proofing-raises-the-house-the-floodplain-lowers-the-water?from=guide) — Elevation, dry and wet flood proofing change the damage; the depth that arrives is shaped upstream
5. [wind mitigation is the house's job. the surge is the coast's](/guide/wind-mitigation-is-the-houses-job?from=guide) — The roof and its connections hold the wind; reefs, mangroves and dunes work on the water
6. [managed retreat leaves land behind](/guide/managed-retreat-leaves-land-behind?from=guide) — A buyout moves the exposure; the land it leaves can become floodplain someone has to keep
7. [every mitigation strategy has two halves](/guide/every-mitigation-strategy-has-two-halves?from=guide) — Harden what you own, keep what you stand on: a peril-by-peril map