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fire retardant sheathing over metal deck?

C

ccollings

SAWHORSE
Joined
Sep 4, 2020
Messages
120
Location
Cleveland
we are installing metal roofing over plywood sheathing on 1 1/2" metal deck for a IIB exterior pavilion. my question is does the plywood sheathing need to be fire retardant treated? my interpretation is no because it's not part of the roof structure.
 
What exception are they trying to apply? I do not agree with SteveRay in that calling it a nailer is sufficient to grant exception. Perhaps they are thinking Exception #18; however, 803.15 applies to interior finishes and not exterior roof assemblies.

For that reason, I say that it must be FR treated per Item #1, Condition #3.

603.1 Allowable Materials
Combustible materials shall be permitted in buildings of Type I or II construction in the following applications and in accordance with Sections 603.1.1 through 603.1.3:
  1. Fire-retardant-treated wood shall be permitted in:
    1. Nonbearing partitions where the required fire-resistance rating is 2 hours or less.
    2. Nonbearing exterior walls where fire-resistance-rated construction is not required.
    3. Roof construction, including girders, trusses, framing and decking.
      Exception: In buildings of Type I-A construction exceeding two stories above grade plane, fire-retardant-treated wood is not permitted in roof construction where the vertical distance from the upper floor to the roof is less than 20 feet (6096 mm).
    4. Balconies, porches, decks and exterior stairways not used as required exits on buildings three stories or less above grade plane. Approved connector shall be in accordance with Section 2304.10.5.
  2. Thermal and acoustical insulation, other than foam plastics, having a flame spread index of not more than 25.
    Exceptions:
    1. Insulation placed between two layers of noncombustible materials without an intervening airspace shall be allowed to have a flame spread index of not more than 100.
    2. Insulation installed between a finished floor and solid decking without intervening airspace shall be allowed to have a flame spread index of not more than 200.
    3. Foam plastics in accordance with Chapter 26.
    4. Roof coverings that have an A, B or C classification.
    5. Interior floor finish and floor covering materials installed in accordance with Section 804.
    6. Millwork such as doors, door frames, window sashes and frames.
    7. Interior wall and ceiling finishes installed in accordance with Section 803.
    8. Trim installed in accordance with Section 806.
    9. Where not installed greater than 15 feet (4572 mm) above grade, show windows, nailing or furring strips and wooden bulkheads below show windows, including their frames, aprons and show cases.
    10. Finish flooring installed in accordance with Section 805.
    11. Partitions dividing portions of stores, offices or similar places occupied by one tenant only and that do not establish a corridor serving an occupant load of 30 or more shall be permitted to be constructed of fire-retardant-treated wood, 1-hour fire-resistance-rated construction or of wood panels or similar light construction up to 6 feet (1829 mm) in height.
    12. Stages and platforms constructed in accordance with Sections 410.2 and 410.3, respectively.
    13. Combustible exterior wall coverings, balconies and similar projections and bay or oriel windows in accordance with Chapter 14 and Section 705.2.3.1.
    14. Blocking such as for handrails, millwork, cabinets and window and door frames.
    15. Light-transmitting plastics as permitted by Chapter 26.
    16. Mastics and caulking materials applied to provide flexible seals between components of exterior wall construction.
    17. Exterior plastic veneer installed in accordance with Section 2605.2.
    18. Nailing or furring strips as permitted by Section 803.15.
    19. Heavy timber as permitted by Note c to Table 601 and Sections 602.4.3 and 705.2.3.1.
    20. Aggregates, component materials and admixtures as permitted by Section 703.2.2.
    21. Sprayed fire-resistant materials and intumescent and mastic fire-resistant coatings, determined on the basis of fire resistance tests in accordance with Section 703.2 and installed in accordance with Sections 1705.14 and 1705.15, respectively.
    22. Materials used to protect penetrations in fire-resistance-rated assemblies in accordance with Section 714.
    23. Materials used to protect joints in fire-resistance-rated assemblies in accordance with Section 715.
    24. Materials allowed in the concealed spaces of buildings of Types I and II construction in accordance with Section 718.5.
    25. Materials exposed within plenums complying with Section 602 of the International Mechanical Code.
    26. Wall construction of freezers and coolers of less than 1,000 square feet (92.9 m2), in size, lined on both sides with noncombustible materials and the building is protected throughout with an automatic sprinkler system in accordance with Section 903.3.1.1.
 
classicT said:
What exception are they trying to apply? I do not agree with SteveRay in that calling it a nailer is sufficient to grant exception. Perhaps they are thinking Exception #18; however, 803.15 applies to interior finishes and not exterior roof assemblies.

For that reason, I say that it must be FR treated per Item #1, Condition #3.

603.1 Allowable Materials
Combustible materials shall be permitted in buildings of Type I or II construction in the following applications and in accordance with Sections 603.1.1 through 603.1.3:
  1. Fire-retardant-treated wood shall be permitted in:
    1. Nonbearing partitions where the required fire-resistance rating is 2 hours or less.
    2. Nonbearing exterior walls where fire-resistance-rated construction is not required.
    3. Roof construction, including girders, trusses, framing and decking.
      Exception: In buildings of Type I-A construction exceeding two stories above grade plane, fire-retardant-treated wood is not permitted in roof construction where the vertical distance from the upper floor to the roof is less than 20 feet (6096 mm).
    4. Balconies, porches, decks and exterior stairways not used as required exits on buildings three stories or less above grade plane. Approved connector shall be in accordance with Section 2304.10.5.
  2. Thermal and acoustical insulation, other than foam plastics, having a flame spread index of not more than 25.
    Exceptions:
    1. Insulation placed between two layers of noncombustible materials without an intervening airspace shall be allowed to have a flame spread index of not more than 100.
    2. Insulation installed between a finished floor and solid decking without intervening airspace shall be allowed to have a flame spread index of not more than 200.
    3. Foam plastics in accordance with Chapter 26.
    4. Roof coverings that have an A, B or C classification.
    5. Interior floor finish and floor covering materials installed in accordance with Section 804.
    6. Millwork such as doors, door frames, window sashes and frames.
    7. Interior wall and ceiling finishes installed in accordance with Section 803.
    8. Trim installed in accordance with Section 806.
    9. Where not installed greater than 15 feet (4572 mm) above grade, show windows, nailing or furring strips and wooden bulkheads below show windows, including their frames, aprons and show cases.
    10. Finish flooring installed in accordance with Section 805.
    11. Partitions dividing portions of stores, offices or similar places occupied by one tenant only and that do not establish a corridor serving an occupant load of 30 or more shall be permitted to be constructed of fire-retardant-treated wood, 1-hour fire-resistance-rated construction or of wood panels or similar light construction up to 6 feet (1829 mm) in height.
    12. Stages and platforms constructed in accordance with Sections 410.2 and 410.3, respectively.
    13. Combustible exterior wall coverings, balconies and similar projections and bay or oriel windows in accordance with Chapter 14 and Section 705.2.3.1.
    14. Blocking such as for handrails, millwork, cabinets and window and door frames.
    15. Light-transmitting plastics as permitted by Chapter 26.
    16. Mastics and caulking materials applied to provide flexible seals between components of exterior wall construction.
    17. Exterior plastic veneer installed in accordance with Section 2605.2.
    18. Nailing or furring strips as permitted by Section 803.15.
    19. Heavy timber as permitted by Note c to Table 601 and Sections 602.4.3 and 705.2.3.1.
    20. Aggregates, component materials and admixtures as permitted by Section 703.2.2.
    21. Sprayed fire-resistant materials and intumescent and mastic fire-resistant coatings, determined on the basis of fire resistance tests in accordance with Section 703.2 and installed in accordance with Sections 1705.14 and 1705.15, respectively.
    22. Materials used to protect penetrations in fire-resistance-rated assemblies in accordance with Section 714.
    23. Materials used to protect joints in fire-resistance-rated assemblies in accordance with Section 715.
    24. Materials allowed in the concealed spaces of buildings of Types I and II construction in accordance with Section 718.5.
    25. Materials exposed within plenums complying with Section 602 of the International Mechanical Code.
    26. Wall construction of freezers and coolers of less than 1,000 square feet (92.9 m2), in size, lined on both sides with noncombustible materials and the building is protected throughout with an automatic sprinkler system in accordance with Section 903.3.1.1.
Click to expand...
my response is that the plywood is not part of the roof construction per item 1 condition 3. the decking is metal deck. the plywood is on top of the roof construction and is only an attachment surface for the metal roofing. honestly i don't feel strongly enough to go to bat over, so i'm ok with making it fire retardant treated.
 
ccollings said:
my response is that the plywood is not part of the roof construction per item 1 condition 3. the decking is metal deck. the plywood is on top of the roof construction and is only an attachment surface for the metal roofing. honestly i don't feel strongly enough to go to bat over, so i'm ok with making it fire retardant treated.
Click to expand...
So which of the 26 exemptions do you think applies? FRT is an allowance. Otherwise, wood is not permitted unless it meets one of the 26 exemptions.
 
Call it foam and then it will be OK.... :rolleyes:

That is my point.....we can cover the roof in combustible foam, but wood is not allowed because the foam folks got foam in....The wood industry may not care because FRT would be allowed and it is wood either way....Is putting a plywood deck over a steel deck any less safe than foam? Does it add a larger fuel load? Doubt it, but not allowed for some logical reason I am sure.... :rolleyes:
 
just to continue the conversation, my feeling is that the plywood is part of the roof covering per 1505.1 for a class 'c' roof and is not part of the roof structure. it's a single story structure, 5244 sqft.
 
yeah, VB would have been the way to go. originally it was metal roofing on densglass and hat channels on metal deck. it was all non combustible so IIB seemed like the right move. now the contractor wants to go with plywood instead of the densglass and hat channels. i'm ok with requiring the plywood to be fire retardant treated.
 
ccollings said:
i'm ok with requiring the plywood to be fire retardant treated.
Click to expand...
Fire retardant treated wood is very corrosive. I think you will need some kind of barrier to keep the plywood from having direct contact with the metal
It is not to late to change the classification and forget the fire retardant treated plywood
 
They allude to no issues with steel framing if installation instructions are followed but the installation instructions are hard to find....

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