These fires can jump a 10 lane freeway - the last one by our house did this. So you would need a pretty wide moat.

But it would probably still help. It doesn't have to be perfect to help firefighters out.

The moat won’t work as well as you probably think. A lot of the problem comes from the sky raining down embers on flammable roofs and such...

This is why the building code in high risk areas should require Class A fire resistant roofs. This won't protect homes from huge firestorms but they're effective against falling embers.

https://www.thisoldhouse.com/roofing/21018219/fire-resistant...

A moat is not a horrid idea.

When Paradise was burning I was thinking if I lived in a fire prone envionment; I would have sprinklers on roof of my home. It would be a simple 1/2" copper pipe feeding a few sprinkler heads on the roof. Maybe a few mercury switches placed around the property, or remotely controlled through the phone line, wifi, or sat phone enabled? Nothing too elaborate. It wouldn't protect everyone. It might save a few house fires that were started with embers though?

I know there one company selling roof fire sprinklers. I know of one small city who's experimenting right now with roof sprinklers. Hell, I wouldn't mind firing a bunch of Firefighters, and seeing that money go to Roof Sprinklers. (I haven't quite figured out exactly what Firefights do all day, with the hard exception of Paramedics. Buildings in cities don't burn like they used too. Wood stick homes in the country are another story.)

I heard one guy say that there wouldn't be enough water pressure if everyones roof was on, but that doesn't make sence either. Not everyone's roof sprinklers would be going off simultaneously if properly implemented, and designed. Firehouses could be in charge of which houses sprinklers go off?

Right now in CA, if you live in a fire prone area, Insurance (Property) is not suspose to be higher. As much as I despise Insurance companies--this provision needs to be nixed. (I don't think it will happen because Insurance companies use it to raise our city insurance rates, and politicians have northern cabins.

A small residential fire sprinkler head outputs around 15gpm of water. While keeping a roof wet is different than wetting down a room on fire, a roof is big and you need to be sure it stays wet, so let's say you want to keep it wet with 30gpm.

And lets say you have to keep it wet for 24 hours until the fire danger passes. That's around 40,000 gallons of water.

Where are you going to get that water? You can't count on the local utility keeping pumps running. If you're lucky you have a well, but a good residential well would yield around 10gpm, and if you and your neighbors are all pulling out water at the max rate together for hours or days, it may run dry while you wait for water to percolate in.

So you need a huge tank of water - a 50,000 gallon tank is around 35 feet in diameter and 7 feet high. Hope you have a big yard and lots of money, the tank alone will probably cost $30K. So figure around $50K to install the system. I hope you have a big back yard for it.

That bunch of firefighters you want to get rid of help protect many square miles of land, putting that $50K sprinkler system on 10,000 homes would cost $500M - that's a lot of firefighters and equipment.

I think there are better ways to keep your roof from burning, but even a metal roof is no guarantee that your house will survive a large wildfire unless you also keep the land devoid of fuel. And you could still fall victim to a piece of flying ember that happens to land on a vulnerable spot of your house.

Don't forget that most of the water you sprinkle onto the roof will collect in the gutters which can feed immediately back into the tank, so you only need enough water for a few cycles plus 24 hours of evaporation loss - still a decent amount of water, but a lot more like a large garden water-butt than an industrial tank.

Huh. That's clever and I've never seen it.

Probably not of much value as roofs are (or can be) relatively fireproof.

The issue is vents, decks, windows to some extent.

That sounds like moderately more flow than needed for much longer than needed. Based on some searches for bushfire tanks, you could meet the water storage recommendations for $3k.

And sure, the idea of replacing the fire department is probably not great, but it wouldn't hurt to have a bunch of these around.

I think getting rid of firefighters and installing hoses on your roof is probably not the idea of the century. Do you suppose its the asphalt catching on fire?

Houses burn (usually) because they have vented attics that embers can blow into. Fire screening your attic or not using vented attics altogether, along with concrete and masonry construction and reasonable vegetation management go a long way toward protecting structures but the fact that structures are there in the first place is the problem.

You can't take an ecosystem based on periodic fire cycles and turn it into a suburb and expect everything to continue to work. Forests need to burn a little bit all the time or they will burn a lot all at once.

While these are earnest and constructive suggestions that would work in some contexts, I'm not sure you're taking the drought conditions into account. The basic problem we have in California is that water levels are hitting historic lows while forests are bone dry and so are the winds that fan fires.

I also suspect that the change in the precipitation mix from snow to rain served to dry out a lot of these areas.

While sprinklers are probably impractical as they require large storage or that you (and your neighbors) starve the mains, I'll bet that a person could design a fast-to-deploy thermal blanket system of some sort.

Probably more effective to mandate less flammable construction, and stop forcing insurance companies to cover homes that have burned multiple times.

How does the insurance thing work?

(my broad understanding is that property insurance is a relatively functional market where they won't underwrite a policy that doesn't make sense)

Insurers aren't perfect. For example, the Northridge earthquake was so expensive it caused insurance companies to exit the California earthquake insurance market. Now the state provides earthquake insurance with high deductibles.

I wouldn't be surprised to see wildfires go a similar route in California if the situation isn't resolved.

It’s already like that. Most houses in the Tahoe area that are surrounded by a certain amount of trees are insurable only via the California FAIR plan.

I keep waiting for the insurance war that will break out due to 'managed retreat' by the Coastal Commission.

As someone else said, it's easy to have either extremely high insurance rates or unavailable insurance if you live in the wrong area on someone's map. The result was FAIR plans with add-ons from insurance companies.

California also has government sponsored fire insurance for property owners that can't obtain commercial insurance. While this is good for individual property owners it's not really fair that taxpayers have to subsidize them. We're not allowing the free market to efficiently price in risks.

https://www.cfpnet.com/

Subsidized, but not fully sponsored. I live about a mile outside the edge of the 2021 CZU fire, and our insurance costs about tripled, even with the CA FAIR plan. We’ve followed the CalFire “defensible space” guidelines and covered vents with fine screen, but improving survivability for that existing house from there would mean reroofing with metal or tile, removing or replacing all wooden decking, and covering T-111 siding with stucco or stone. Not cheap. Also effectively a different house. Multiplied by all the homes in woodlands, still not cheap. For anyone who has always wanted to live in the woods, consider living near the woods instead.

Yeah those retro-fits would be very expensive. It doesn't make a lot of sense to me that insurance companies paid to rebuild a lot of homes out of materials that aren't suitable for the homes' fire risk. Though, I don't have a ton of knowledge about this.

The insurance thing is interesting. Along the gulf coast insurance has retreated over time, and There are no significant areas that used to be developed that got wiped out in a hurricane and were not rebuilt. Perhaps the same will happen in California.

Winds can carry burning debris hundreds of feet through the air, so it'd need to be more like a village in the middle of a lake. Though it wouldn't have to be a lake, just a barren field that has no (or limited) combustables. But would still need to be quite large for protection, and buildings would still need to be fire resistant to protect against burning embers.

Can we just build something like a Helms Deep?

If communities would just follow the damn guidelines(https://www.fire.ca.gov/programs/communications/defensible-s...) they'd be a lot better off.

Moats are good at preventing barbarians from attacking your city not stopping a wildfire.

While the forest around them burns, what would the townspeople breathe?

Moats have a tendency to evaporate unless you keep them full. I could see it getting expensive.

Need a massive moat, spot fires from embers can cross large rivers already in high wind events.

A moat won't protect from flying embers.