Tile Roof: Vertical Ventilation

BY GIBBY GORMAN

The sight of red “Spanish” tile roofs is becoming commonplace in subdivisions across the United States. Up to 80 percent of new residential construction in the Sunbelt regions contain some form of tile roofs. For the homeowner, these roofs offer several positive aspects such as less maintenance and a longer life expectancy. For firefighters on the fireground, however, this roof presents a number of challenges. To vertically ventilate a tile roof home, the incident commander (IC) should first apply the “risk vs. gain” analysis to determine if going to the roof is an option. If it is, the IC should follow a ventilation game plan specific for tile roofs and be aware of the hazards of operating above them. The usual tactical mindset of ventilating with asphalt shingles or built-up roof construction doesn’t fit the profile of tiled roofs in part because of the extra weight supported by lightweight trusses under fire conditions.

Tile Roof Construction Features

Following is some general information pertaining to tile roofs:

  • The most common types of tiles include concrete and clay. Clay tile is baked molded clay. A surface treatment may be applied. The tiles come in a wide variety of profiles, styles finishes, and installation modes. The tiles can be one piece, two piece, interlocking, or flat. Firefighters should also be aware that some look like shake shingle or plastic/composite tiles.
  • Concrete tiles are made of Portland cement, sand, and water. The material is mixed and extruded on molds under high pressure; the tiles generally have lugs on the undersides for anchoring to batten strips. Battens are 1- × 2-inch strips of wood attached to the roof over the felt paper and are spaced according to the length of the tile. It is common in a 3:12 to 5:12 pitch roof to have the first three courses (rows) of one-piece tile nailed individually as they are placed around the perimeter of the roof, including the bottom, top, and sides. As the steepness of a roof increases, as in an 8:12 pitch, every other row is nailed; in a 12:12 pitch, every tile is nailed in. Roof pitch is the angle of the roof surface above the horizontal plane; roofers generally refer to it as the “rise over run.” The “rise” is the inch measurement of the vertical rise of the roof per foot of horizontal distance, which is called the “run.”
  • The nailing pattern is important information to know when you are using your trash hook or other tool to lift up a piece of tile to “sound” the roof below it or if you want to remove tiles to create an open area to cut your vent hole.
  • The weight of a one-piece clay tile is approximately 12 pounds, and a one-piece concrete tile weighs approximately eight to 10 pounds. Clay and concrete tiles are about 12 inches wide and about 16 to 17 inches in length. (Note: There are many styles and shapes of tile that may be different weights or sizes than those listed here.) Felt paper is applied over the roof deck, which, in most cases, is oriented strand board (OSB).

Roof tiles can be secured to the roof in various ways. The method is selected based on wind, deck type, slope, building codes, local practices, or manufacturer recommendations. Nails are the most common method of attachment, but they may also be attached with wire tie and strapping systems, clips, or lugs.

Subdivisions selling tract homes will often offer the homeowner one of several models to choose from; each design has unique truss construction features based on whether, for example, it is a gable or a hip-style roof. The trusses are usually constructed of lightweight, prefabricated lumber held in place with gusset plates. A standard residential roof load design is about 45 pounds per square foot (psf); that is based on 20-25 pounds psf for the dead load, consisting of the tile, wood decking, trusses, electrical wiring, and insulation and 20 pounds psf for the live load, which could be the workers.

A visual analogy of the weight atop a roof would be to picture a tractor trailer weighing about 34,000 pounds parked on top of a 2,000-square-foot home that uses concrete tiles. That is what a typical tile roof load for a home that size would equate to, which is still within the weight limits for the roof load. However, it can be a real critical fireground factor with fire impinging on the truss work. The actual liveable area for that size home would total about 3,300 square feet, including the porch, foyer, and eaves. Using the formula of one tile equals one foot in width, you also get about 3,300 pieces of tile attached to that roof.

In different regions of the United States, roof pitches or environmental concerns may change the design load, and custom home design loads are specific to construction features the homeowner desires. Preplanning homes in the subdivisions in your first-due area during the construction stage to visualize the trusses can pay big dividends down the road.

To Vent or Not to Vent

When a ladder company and the IC make a decision to vertically ventilate, they do so by knowing the location of the fire and properly reading the smoke. They are also aware of their additional weight in a concentrated area with possible fire impingement onto the trusses and gusset plates.

Other factors firefighters should be aware of include the following:

  • The concrete or clay tiles may cover any damaged or sagging roof areas, hiding unsafe sections of roof.
  • There will be increased time on the roof because you will have to remove the tiles to create an area to cut the vent hole.
  • You cannot determine if the original roof was replaced with tiles and if the support system was correctly modified to carry the additional weight.
  • Tile roofs can become slippery when wet or in colder weather when they are coated with frost or snow.

The initial size-up should determine whether you will be able to perform vertical or horizontal ventilation successfully or if another form of ventilation would be more appropriate and safer. An alternative would be to remove the gable ends and allow the smoke and heat to release from the opening. You can accomplish this with a chain saw or a pike pole. If you use a chain saw, use a leg lock on the ladder and determine if there will be two sawyers and two ladders or one sawyer and one ladder. A pike pole or other similar tool can pull out the gable ends or frame, depending on how it is nailed in; working from the safety of the ladder bucket can help in accomplishing this task. Another choice is to use a positive-pressure attack (PPA) in a coordinated approach in relation to the position of the interior crew and the seat of the fire. Make sure when forcing air into the structure that you do not put the interior crew in harm’s way. With PPA, breaking out a “hot” window allows the heat to vent out ahead of a fresh air opening created, for example, when crews enter a front door. There is no one-size-fits-all choice here; they are tools in the toolbox. Departments must follow their standard operating procedures (SOPs) and discuss ahead of time options for ventilation. Some of the factors to help make that decision include the following:

  • What’s burning? If the fire is isolated in the attic, the ladder captain should confirm if interior crews need to keep the roof in place to accomplish conversion. Conversion will likely be more effective with the roof intact, which creates a void area for the expansion of water into steam to occur. Ladder crews may be able control the directional spread of fire with a properly located offensive ventilation opening. Make sure to have enough roof real estate to position your crew to cut over smoke while being as close to the fire as is safe to do so to avoid working over fire-weakened trusses. Truss failure in a short period of time is possible with direct fire impingement in an open web lightweight truss system because there is more surface area exposed to the flame and the fire may have been hidden in the void space and allowed to consume the small dimensional wood. Vertical ventilation under these conditions pushes the “risk” scenario to the maximum. In this circumstance, removing the gable ends for ventilation and opening up small holes in the ceiling from below to attack the fire in the attic with handlines may be a more suitable tactic.
  • If the location of the fire is “room and contents” that has not yet had direct impingement on the truss system, conditions on the inside will get hot quickly based on how modern furnishings burn. Because of the potential for a flashover, the safety of the interior crew and their ability to carry out a primary search will benefit from vertical ventilation. Sometimes in these types of fires, horizontal ventilation may be another tactical method to use.
  • Taking a quick look at the sides and rear of the structure before accessing the roof will offer clues as to where the seat of the fire is and help indicate where to spot the ladder from the unburned side.

Venting the Roof

Prior to “making” the roof, you can make a small inspection hole on the interior to the load-bearing wall to confirm that the attic conditions match what is seen from the outside. Simply push back a tile and use an ax or a chain saw to open up a small section of roof decking. Make sure it is interior of the load-bearing wall. In addition, the first interior firefighter with a hook can quickly make an inspection hole into the ceiling and read conditions above. Relaying this information to the IC and the roof team can enhance the decision on the risk vs. gain analysis and conditions in the truss loft.

When removing tiles to create an open space to vent, remember roof rafters are typically 24 inches on center; pushing up three tiles at the base of the roof before walking upward should create enough room to find a center rafter by sounding or using a back cut with the chain saw. A back cut is simply using your saw blade to cut through the roof until you feel resistance, indicating the presence of a rafter. Smashing tiles instead of manually removing them is fast, but the process creates many small pebble-like pieces that can make the area slippery, become projectiles when the chain saw blade hits them, or can roll down onto firefighters below the roof.

If you have a three-person crew, leave the firefighter operating the chain saw below the cut area safely waiting above the load-bearing wall, and have the other two firefighters individually remove a three-tile width on each side of a center rafter (located earlier). This process should create a six-foot open vent area; clear an approximately six-foot upward length as well.

Sound the roof decking to ensure it is still solid as you remove tiles. Stacking the tiles as you go keeps them from rolling down the roof and potentially injuring someone below. Stacking the tiles in manageable piles on the unburned side of the vent hole, if possible, would allow for the more stable portion of the roof to support the additional weight.

The sawyer, who, incidentally, should be fresh since he has not worked to remove the tile, can walk up the center rafter and begin his center rafter louver. The louver cut is a sequence of cuts that starts inside one rafter and rolls over the second (center) and stops at the third rafter, creating a way to louver the roof by pivoting it on top of the center rafter. Creating a vent hole midway up to the peak will still allow for a good release point for heated gases and allow firefighters to work below the top three rows of tile, which will probably be nailed in. This should speed up operations, reducing time on the roof and making it safer for the crew.

The captain must have great situational awareness during this process to ensure his crew is safe to perform the ventilation function, and he must continue to evaluate fire conditions to make sure his actions safely fit into the risk vs. gain scenario.

Once the vent hole is complete, the crew will retrace the crew’s path off the roof as the captain “sounds” the roof to the exit point and gives the IC a roof report when it is safe to do so. This will be followed up with a personnel accountability report, the lowest self-contained breathing apparatus air level of the crew when on the ground, and whether or not the crew is ready for reassignment.

The decisions of whether and, if so, how to vertically vent a residential tile roof will vary in fire departments across the United States. Each department has its own SOPs that spell out the choice. If your department does go to the roof on these types of fires, knowing the tile construction features, having a specific game plan, and practicing that plan can help make a dangerous situation a little safer. Remember to ventilate over smoke, not fire. If going to the roof is not an option, your department can use other methods for ventilating a structure.

GIBBY GORMAN has been a battalion chief for the Maricopa (AZ) Fire Department for the past year after a brief retirement. Previously, he retired as a captain with more than 26 years of service with the Tempe (AZ) Fire Department. He spent 14 years on a ladder company and was a member of the technical rescue team (TRT) for 12 years and a regional TRT coordinator for five years. He was also a member of the department’s SCUBA rescue team since its inception in 2006 and has been a hazmat tech for four years. During his career, he was heavily involved in the department’s ladder training and probationary firefighter training and assisted with promotional tests, developed classes, and instructed for regional ladder training programs. He taught firefighter I and II at the community college level for 10 years and assisted with the Arizona State Fire School. He runs Southwest Firefighting Concepts, a consulting firm that focuses on ladder tactics and leadership development.

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