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JulieHowe
10-16-2009, 06:02 AM
I need some advice on arson. Here's the scenario:

This is a mansion way up high in the canyons, in Southern California, with a sophisticated fire alarm system and sprinklers on the roof. The time frame is the summer of 1986.

For someone perpetrating a deliberate act of sabotage, how difficult would it be to bypass the roof sprinkler system and the fire alarm system (similar to the ones found in commercial buildings)? The arsonists aren't geniuses, but they're white supremacists who have a strong motivation to make sure the house burns down, with the family inside.

Nobody in the house dies, and everyone gets out safely, but the house is a total loss and will have to be rebuilt. Is the roof the most logical ignition point for this fire? Also, is all of this plausible? The house was built in the 1950's.

Thanks in advance.

hammerklavier
10-16-2009, 07:10 AM
Since it's up high, it probably has its water pumped up to it. Kill the pump, cut the electricity and, if it is made of wood, set it on fire. If the sprinkler system is hooked to an onsite water storage tank or cistern, then some more sophisticated plumbing sabatoge is necessary to kill the sprinklers. Also, if they have a backup generator, they would have to kill that. Finally, if the alarm itself has backup power, they would have to get inside and disable it at the alarm console.

JulieHowe
10-16-2009, 08:33 AM
Thanks!

jclarkdawe
10-16-2009, 05:31 PM
Let's start with the sprinkler system. By a "roof" system, I am going to assume that means a storage tank on the roof. This tank would probably be 100 gallons (about 800 pounds weight) although for large buildings these tanks can go up to 500 or more gallons (2,000 pounds or more). The system is designed around gravity and feeds downhill to the sprinkler heads. Absolutely no outside source is required for the system in the first few minutes as it just drains the tank.

Pressure is provided by a big pipe that becomes progressive smaller. And initially, you don't need a hell of a lot of water to put out a fire. If the system is part of a municipal water supply system, a pipe connects from the municipal system up to the tank and would replenish the tank as it drains in a fire, regardless of the power supply. If it is supplied by a well, the tank would refill until the power goes out.

Then the system would have an external pipe for the fire department to hook into, anywhere from one to two and half inches. When the first fire engine arrives, it will hook up to this line and supply the water for the sprinkler system that way. These pipes can be seen on many large buildings.

Somewhere in the house, these three supply routes come together. Any destruction prior to that point causes the other supplies to kick in. If there are blueprints of the house, it will show this plumbing system, which is separate and distinct from the household's system.

Okay, now that you understand how its built, you can begin to think about how to destroy it. Simplest approach is to take a sledge hammer to a couple of sprinkler heads. This will cause two massive leaks and the balance of the system with no water. Second approach would be to cut the pipe where the three systems have come together. Third approach is to cap each sprinkler head. None of these approaches are very quiet to do and all have to be done on the inside of the house. Any drop in the water pressure in the system causes an alarm to go off for the fire department to respond. In other words, these things are designed to make sabotage difficult.

What has been done is if the fire department has a long response time is to cut the external supply line outside the building and work at building a big enough fire inside so that it can take hold despite the storage tank. It takes a lot of fire, and you'll need a fairly massive amount of gasoline to accomplish this.

Now moving on to the alarm system, I would presume anyone who has a sprinkler system that they retro-built into the building (a house, even a mansion, would not have had a sprinkler system in the 1950s) has a fairly sophisticated system. My guess is it would have an external power source, an internal battery system, and a backup battery system to warn of no power in the event the first two failed. In other words, you cut the power line to the house, nothing happens and it switches to the battery. Exactly what it's designed to do in the event of a power failure. If the battery is dead or disconnected, a second, very internal battery would then be triggered, sending a trouble signal to the alarm company. This second battery is next to impossible to find and even harder to disconnect (it's designed that way).

Net result with a quality system is that unless you know how the panel is built, you can't kill the thing. In other words, these things are designed around avoiding idiots killing them.

Your boys are going to have their work cut out for them, or you're going to have to reduce the protection level. There's a lot of cheap crap out there that the homeowner could have been suckered into.

Best of luck,

Jim Clark-Dawe

JulieHowe
10-16-2009, 09:42 PM
Your boys are going to have their work cut out for them, or you're going to have to reduce the protection level. There's a lot of cheap crap out there that the homeowner could have been suckered into.

That's what I thought. I'll probably lower the protection level. Thanks :)

jclarkdawe
10-17-2009, 01:40 AM
I wasn't thinking about your location when you first posted. A rooftop sprinkler system could also be a sprinkler system to protect the roof in case of brush fires. I don't know anything about those.

Sprinklers are placed either on the ceiling or the top of the wall, depending upon the design. They are not placed on the roof (might be in the attic under the peak of the roof).

Simpler sprinkler system that's pretty good is no storage tank and tying it to a municipal water system. One pipe comes into the house, and splits for the house supply and the sprinkler system. Usually it does not come with an alarm system. Easily stopped by shutting the water off outside. There's a little cover, about six inches in diameter. Lift the cover and you stick a long socket wrench into the hole. Turn valve with wrench and the water is shut off. You can do this in less than five minutes. Most municipal water systems have a shutoff for each building.

This system would still have a stand pipe for the fire department, but by the time they arrive, you could have the house seriously in flames.

For alarm systems, have the home owner put in a system with his handyman. Unless the handyman is seriously talented, the system can be relatively easily disabled. It could be done as easily as disconnecting the power and would if it has no battery supply. If the area doesn't have frequent power outages, why bother with a battery?

As far as an ignition point, the lower in the structure the better. Fire burns up easily, down poorly. Best place would be the front entrance way. This blocks the easiest egress and provides the fire with a stairwell to go up.

Best of luck,

Jim Clark-Dawe

Mark G
10-17-2009, 02:16 AM
I think dumb "brute force" guys tend to use tools they're familiar with. Guns, explosives, trucks, dogs, alcohol, etc.

What's the exterior made of? If it's flammable, then maybe they'd soak the outside with gasoline and light it up.

Another thing they could do is hijack a truck with a big bulldozer, and mow down the house.

Then again, a Uhaul truck loaded with 1000 lbs of manure and some diesel fuel, parked on the front porch, might make a crater where the house used to be...

Kathie Freeman
10-18-2009, 09:13 PM
Since the house in on a hillside most of it will be on stilts. Start the fire in the dry brush under the floor with lots of combustibles (eg.gasoline-soaked rags and firewood), and by the time the sprinkler system is activated the support beams will already be compromised, the subfloor will be in flames, and the house will almost certainly come down. They need to be careful with the gasoline, though, have a "trail" at least 40-50 feet long, or they will go up with it.

Tsu Dho Nimh
10-19-2009, 06:59 PM
I need some advice on arson. Here's the scenario:

This is a mansion way up high in the canyons, in Southern California, with a sophisticated fire alarm system and sprinklers on the roof. The time frame is the summer of 1986. .
Typically, kill the power and you kill the fire alarms.


For someone perpetrating a deliberate act of sabotage, how difficult would it be to bypass the roof sprinkler system and the fire alarm system (similar to the ones found in commercial buildings)? The arsonists aren't geniuses, but they're white supremacists who have a strong motivation to make sure the house burns down, with the family inside.

Inconspicuous: Depending on the landscaping, I'd start a brush fire in several spots around the mansion, below it because fire moves best uphill.

Bringing in dried brush and ensuring that there is a trail of dried brush to the house and brush piled against the lower part of the house. Fire moves up faster than it does down.

Obvious: Cut the alarm wires and the power to the pump that feeds the sprinklers. Throw firebombs in every window and lob a few onto the roof.

JulieHowe
10-20-2009, 12:21 AM
Thanks!!