1. Room Fires etc 2. Porch Fires etc 3. Nozzles etc 4. Flame Length etc 5. Cockloft Fires etc 6. GPM and Safety Margins etc
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5)Cockloft Fires etc

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1st draft 9Aug21 Latest rev 25Aug24
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Three-story, wood-frame residential building with cockloft — Fig. 5-1 Three-decker with cockloft

Extinguishing a cockloft fire is about wetting the burning fuel surfaces and ventilating skillfully. It's important not to stray from that mental model.

Gut reaction for many FFs is to “get ahead” of the fire and put water on its farthest reach. But control is not about working the leading edge.

Water should be applied to burning fuels (seat of the fire), not the leading edge of flame spreading across underside of roof deck — Fig. 5-2 Wet the pyrolyzing fuels, not the leading edge

Long flames across the underside of a roof deck can extend over a big area that is not pyrolyzingHeat-driven processes that produce fuel gases from solid and liquid fuels yet. Applying water in that area can push the flame around, but it won't be an easy or effective way to kill the fire.

Control is about wetting the fuel surfaces Steam inerting and gas cooling can help, but stable progress in cocklofts almost always requires wetting the burning fuel surfaces. See Flame Length etc and Room Fires etc that are already making fuel gases.

Find those surfaces and paint them with water. Start by knowing where the fire came from—how it got into the cockloft. An electrical fire in the top floor ceiling is very different from a fire coming up the walls or chases; and both are very different from an exterior fire coming in through a soffit.

(Don't rely on just a thermal imager to track fire above the ceiling. It takes time for the fire's heat to go through building materials to the ceiling or roof membrane where it's visible to the imager. The delay can throw your decisions off.)

Nozzle held above joists to apply water to burning fuels (seat of fire). — Fig. 5-3 Nozzle above joists

If you do have a ceiling hole out ahead of the flame, you should be throwing water back toward the source of the fire. The gold standard for cockloft attacks is a nozzle held above the joists. The FF (keeping their head and body below the ceiling until the fire is controlled) directs the horizontal stream and sees the effect that it’s having.

Penetrating nozzles are also an option, as are combination nozzles using the sharp angle technique. The key is to wet the surfaces that are actually burning and not just chase flame.

Try to restrict the fire’s air supply by limiting ceiling holes until you’re ready to put water where it's needed. Wind and the building’s cockloft vents may work against you, so be realistic in your expectations.

Cockloft on four-story apartment building. — Fig. 5-4 Cockloft with decorative cornice

No easy rule governs roof ventilation. Make your decision based on conditions, available protective measures, and likely benefits. A roof hole can have some combination of four possible objectives:

draw the fire in a good direction;
turn a horizontal flame into a vertical flame;
remove airborne fuel (AF)In this context, airborne fuel includes pyrolosis gases and partially-burned fuels. See Flame Length etc for a more general discussion.;
improve conditions for the inside crews.

If you're sure that the cockloft is the only space that needs to be vented, consider letting the interior crews keep control of the ceiling—not pushing it down. They might want to limit the fire’s air supply; and they may be able to set up a helpful flow between a ceiling hole and the roof hole.

Check early for two ceilings and/or two roofs.

Etc

Fig. 5-5 Cockloft above residences in converted factory building

The success of a cockloft attack can also depend on putting out fire that is coming up from below (porches, wall voids, chases etc). It may be helpful to think of the two battles as separate jobs and make them separate assignments. Consider physically separating the jobs by using an above-the-joists cockloft attack from another room.

When sizing up fire in walls and chases, don't forget about drop fire from melted tar and/or foamed plastic roofing products.

After the fire, get photos of the roof deck (from above and below) for the after-action review. Also take shots of the fire's path into the cockloft and any building features that helped or hindered your efforts.

Questions

What about difficult top-floor ceilings (multiple layers, wire lath, tin, two ceilings etc)?

Nozzle held above joists to apply water to burning fuels (seat of fire) from a room without a difficult ceiling — Fig. 5-6 Try to find a room without the difficult ceiling

Small-hole approaches (penetrating nozzles, sharp angle Sharp angle technique etc) may work in some situations, but nozzle-above-the-joists is a more reliable solution—especially if you can find a room that doesn't have the difficult ceiling. Bathrooms and kitchens are good starting guesses.

Second ceilings (drop ceilings) were generally installed room-by-room, and any fire in the added voids can be put out room-by-room in a separate battle. Be ready for collapse of the bottom ceiling.

What effect does wind have?

In addition to changing the way fire spreads, wind can ruin your efforts to limit the fire's air supply. It can also restrict ventilation options, make size-up harder, and make sudden changes more likely. It often creates tough decisions.

Nozzle held above joists to apply water to burning fuels (seat of fire) from upwind position. — Fig. 5-7 Upwind position may be best in windy conditions

Try to use the wind to your advantage but don't force a vent option that isn't really available. Don't be distracted by dancing flames. Stay focused on finding and wetting the burning fuel surfaces. If the wind is having a big effect, nozzle-above-the-joists through an access hole at the upwind edge of the fire may be your best bet.

What flow rates are needed for cockloft fires?

It depends on volume of fire and attack method chosen, but it's generally not a big water situation until the roof starts collapsing. In the three-deckers that are common in the U.S. northeast, 50 GPM, hitting the right surfaces, is a lot of water.