1. Chapter 8 Heavy Timber and Mill Construction

2. Objectives
Identify and describe the characteristics of heavy timber buildings and specific characteristics of mill construction (Type IV construction).
Identify the dimensions of heavy timber members.

3. Objectives
Describe why the misnomer “slow burning” is inappropriate for heavy timber buildings.
Identify the specific hazards of these conflagration breeders.
Identify specific problems with mill construction.

4. Objectives
Identify the dangers of concealed spaces in renovated mill buildings.
Identify the differences between new heavy timber buildings and those built in the past.
Describe the hazards of vacant heavy timber buildings and structures under demolition.

5. A History of Mill and Heavy Timber Construction
Buildings with noncombustible or limited-combustible exterior walls and floors made of large dimension combustible materials

6. A History of Mill and Heavy Timber Construction
Type IV construction
Origins in medieval England
Early American settlements
Barns and churches
Courtesy of Glenn Corbett.

7. A History of Mill and Heavy Timber Construction
Courtesy of Joseph E. B. Elliot/Library of
Congress Prints and Photographs Division.
Courtesy of Glenn Corbett.
The Slater Mill in Pawtucket, Rhode Island, built in 1793.
A reinforced concrete factory mimicking the look of heavy timber.

8. Mill Construction Exterior bearing and nonbearing walls are masonry.
Columns and beams are of heavy timber with cast iron connectors.
Courtesy of Glenn Corbett.

9. Mill Construction
Floors are of thick grooved, splined, or laminated planks.

10. Mill Construction
Roofs supported by beams or timber arches and trusses

11. Mill Construction Adequate fire barriers Ends of girders are fire cut
Cast iron box
Corbelled beams
© Justin Kase zsixz/Alamy Images.

12. Mill Construction Scuppers Concealed spaces are eliminated
Courtesy of Glenn Corbett.

13. Mill Construction
Large number of windows provide maximum lighting to mill interior.
Courtesy of Glenn Corbett.

14. Mill Construction Sawtooth mills Vertical openings are protected
Automatic sprinkler system
Special hazards put in detached buildings
© Brians/ShutterStock, Inc.

15. Slow Burning? Proponents of heavy timber construction
Believe “slow burning” means “collapse resistance”
Statement true only if fire department can maintain interior offensive operations

16. Definition of Conflagration Breeder
A structure that presents severe exposure problems that are capable of initiating a large, multiple building fire that is not easily contained

17. Characteristics of a Conflagration Breeder
Radiant heat and fire brands
Large collapse zones
Fire spread
Shut-off sprinkler systems, open equipment shafts, and uncompartmented areas

18. Characteristics of a Conflagration Breeder
Improperly maintained fire doors
Lack of compartmentation
Sealed-up window openings
Stair shafts
Courtesy of Glenn Corbett.

19. Fighting a Conflagration Breeder
Expect the fight of your life.
You need:
Large water supply
Numerous heavy-caliber streams
Large collapse zone
Extensive brand patrol downwind
Luck

20. Conversion, Modification, and Preservation
Remodeling
Often detracts from the original fire characteristics.
Columns may have been removed.
New trusses do not have the inherent resistance of the old columns and beams.
Courtesy of Glenn Corbett.

21. Conversion, Modification, and Preservation
Changes in use
Conversions to tenant factories, storage, discount stores, and apartments
Fire loads are often beyond capacity of the installed sprinklers.
Unsprinklered areas are created
Courtesy of Glenn Corbett.

22. Heavy Timber Building Requires careful maintenance Metal connectors
Full fire sprinkler protection
Renovations and conversion

23. Heavy Timber Building Concealed spaces
Deficiencies should be clearly noted.
Realistic prefire scenarios are required.
Courtesy of Glenn Corbett.

24. New Buildings of Heavy Timber Construction
Type IV construction
Often lacks at least one feature vital for fire safety
Unprotected steel columns, part-steel trusses, unsprinklered void spaces, or no sprinkler protection

25. Heavy Timber Structures
Not being built as commonly
Niche for certain types of occupancies
Modern heavy timber church

26. Heavy Timber Structures
Courtesy of Glenn Corbett
Courtesy of APA - The Engineered Wood Association
A laminated wood truss in a modern church.
Large glue laminated timbers are used to form the roof and walls of this arena.

27. Heavy Timber Structures

28. Heavy Timber Construction Contractors
Be wary of those who claim to be erecting a heavy timber structure.
Many do not know the actual dimensions required.

29. Heavy Timber Theory Heavy timbers are difficult to ignite
Will char on the surface only
Over the years the floors may have been soaked with flammable and combustible fluids.

30. Vacant Buildings Cities with recent massive downtown fires Baltimore
Philadelphia
Lynn (Massachusetts)
Minneapolis
Indianapolis
Montreal

31. Characteristics of Massive Downtown Fires
Old combustible interior masonry buildings
Fire barriers removed or inoperable
Sprinkler systems removed or disabled
Only fuel was the interior structure of the building

32. Vacant Structures Sprinklers are often turned off
Open invitation to arson

33. Sprinkler Systems Full automatic sprinkler protection
“Yard” hydrants may be turned off.
Preplanning
Courtesy of Glenn Corbett.

34. Summary
Heavy timber construction has been used for large structures uniquely vulnerable to fire.
Remodeling has detracted from original fire characteristics.
Heavy timber construction is classified as Type IV construction.

35. Summary Proponents often advance the term slow burning.
Slow-burning characteristic is an advantage only as long as the fire department can maintain interior offensive operations.
Slow burning delays extinguishment and prolongs air pollution.

36. Summary
A building conforming to the code definition of heavy timber construction probably lacks at least one or more of the features vital for fire safety.
Full sprinkler protection is the only fire protection measure that can reasonably be expected to prevent a disaster in a heavy timber building.

37. Summary
Problems arise when buildings are abandoned, are converted into a multiple-unit occupancy, or are prepared for rehabilitation into apartment or office occupancies.
Today, heavy timber structures are not being built in record numbers.
Sprinkler protection is often turned off in vacant buildings made of heavy timber.