Old vacant mills, loft apartments and retail repurposed from former manufacturing plants of heavy timber construction (Type IV) are still regularly found in cities, large and small. Some of the greatest buildings of this unique architecture have been torn or burned down. However the trend to convert these old buildings to modern uses creates new challenges we need to understand.

Typical Features of Mill Construction:

1) Exterior bearing walls and nonbearing walls are solid masonry, usually either brick or stone

2) Columns and beams are usually of massive wood construction supporting floors of thick grooved, splined or laminated planks.

3) Roofs of thick splined or laminated planks are supported by beams or timber arches and trusses

4) The ends of girders are firecut, so as to release in the event of a collapse.

Reference Francis Brannigan : Building Construction for the Fire Service

Before we can understand the challenges of today, we need to take a trip to the past. So what made these buildings dangerous during those times? Improper storage and disposal of combustibles was a major issue. In some factories the machinery would commonly be located on those wooden floors which would absorb the oils and grease from the equipment.

Buildings that had scuppers (wall drains located off the floors) were constantly susceptible to water damage. Open chases and vertical penetrations were common in the early 1900s and depression era construction and who knows what other corners were cut . Like today, there were good and bad builders.

What is happening to these buildings today? In some cases these old factories are still being used and are living pieces of history. In other cases demolition or vacancy looms for idle and vacant buildings. These represent their own hazard as targets for arson.

Let’s look at a popular use for some of these buildings, in this case, the conversion to residential living space. In the fire service we don’t view it as real estate renewal but instead a new occupancy hazards to contend with. New construction being meshed with old can create hidden hazards.

Such a conversion has two scenarios, one with the constant supervision of a well managed municipal building department and the other with little or no supervision. In the pictures shown, the building department strictly enforced the installation of new steel beams, floors and an adequately designed sprinkler system.

Certain sections of this factory were originally occupied by a dye process for curtains. When interviewing the architect, he stated the most damage to the floors and beams was noted near the scuppers. He speculated that the Dye process regularly experienced spills and the workers likely cleaned up the fluid by hosing the dye out the scuppers. Due to the multiple dye marks and staining on the floors and near the scuppers, this theory seems reasonable.

These floors and beams were damaged beyond the point of refurbishment. Imagine if the building dept was not involved and let the builders do what they wanted? Would the outcome have been the same? Many of these Type IV buildings have been vacant for nearly 50 years. In those years, broken windows and no heating resulted in weather exposure to the floors and beams. It is the Author’s opinion that any building under those conditions should never use the original timber beams or flooring.

The new construction is meshed with the old in these revitalization scenarios. In many ways these old buildings are convenient to the builders. They can build their own design within a giant open space. The ceilings are ten feet high as a minimum and in certain parts of the factory they may be as much as fifty feet tall. In refurbishing these buildings, though, watch for , void spaces being built to run the utilities and sprinkler pipes. Local fire departments should pay great attention to where these plenum spaces are and where they travel to.

Because these plenum spaces will be enclosed with sheetrock, the builder does not have to fire proof those timber beams in those spaces, but they still represent a place for fire to travel (pictured above) All of the exposed (Original Heavy Timber) does have to be fire proof. That is the glaze