Fire stops were built into the walls during the era of balloon construction to stop the spread or advancement of fire from one section of a structure to another. The fire stop was just a 2x4 placed horizontally in the wall between the studs at approximately ceiling level. they worked great to prevent fires from traveling up the wall to floor above. However, fire stops have only a limited application in modern construction.

Before fire stops were a requirement in balloon constructed homes you could actually go up into the second or third floor attic and drop an object and it would end up at the bottom of the wall on the lower floor, if not the basement. In effect the wall was an open chimney from the first floor all the way to the attic. If a fire broke out in the lower level the flames would be sucked up into the wall all the way to the attic space. That is why installing wall fire stops were important, to stop the chimney effect of the wall.

As balloon construction went out of style the building codes were updated deleting the requirement for fire stops although it took some time for the code to change in all areas. It isn’t unusual to find older homes that are not of balloon construction with fire stops built into the wall. Just an example of how old habits die hard.

Modern building construction creates effective fire blocks by the house design. The continuous top and bottom wall plates that are part of the wall structure create the fire block. When the modern house is completed with drywall on the inside and or plywood on the outside, the wall becomes a separate sealed compartment between each stud cavity. Nothing can get from one stud cavity to the other unless you cut a hole in either a wall stud or the top and bottom wall plates.

Often in older home remodeling projects the carpenters have to deal with fire stops. They become particularly troublesome when running wiring and plumbing. If the house is not of balloon construction the fire stop can be removed, however if it is a balloon constructed house the integrity of the fire stop must be maintained. In some towns and cities local building codes allow the replacement of the wood fire stop with a fiberglass insulation fire stop.

In modern homes fire stops are often required by local code when there are soffits and tray ceilings design features. These fire stop products are usually northing more than fire stop foam or batt insulation to prevent any chimney effect between the wall and ceiling cavities.

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