Document LKrQjmYjkq8y6q8g5rLrEzpm3
TECHNICAL BULLETIN No. 8
SEVENTH REVISION JUNE 1958
FIRE RESISTIVE
RATINGS
Metal Lath and Plaster
CONSTRUCTION
Fire Resist ance
AUTHORITY
l%" gypsum-vermiculite or gypsum-perlite plaster1, 11 over self-
furring metal lath wrapped around column.
4-hours
Underwriters' Laboratories Retardant 2851-5, 6, dated 5/15/56 and 3187-4, 5, 7
euaei
1J4" gypsum-vermiculite or perlite plaster1, n, over metal lath. Metal
lath furred out 1)4' from column flanges with space between col
umn flanges and lath filled with plaster.
4-hours
Underwriters' Laboratories
Retardants 2851-2, dated S/10/49 and 3187-3, dated 4/24/SO
z
2
1'/," gypsum-perlite plaster1, H, over metal lath. Metal lath furred Vu" from column with Y" channel brackets at approximately 2'
4-hours
Underwriters' Laboratories Retardant 3187-6
vertical spacings.
COLUMNS
STEEL COLUMNS
1" gypsum-vermiculite or perlite plaster1, u, over metal lath. Metal
lath furred out \lY' from column flanges with space between col
umn flanges and lath filled with plaster.
1 Yu" gypsum-vermiculite or gypsum-perlite plaster1, u, over self
furring metal lath wrapped around column.
3-hours 3-hours
Underwriters' Laboratories Retardants 2851-1, dated S/10/49, and 3187-1, dated 1/24/50
Underwriters' Laboratories Retardant 2851-5, 6, dated 5/15/56 and 3187-4, 5, 7
1" gypsum-perlite plaster1, H, oyer metal lath. Metal lath furred out 1)4' from column flanges.
2-hours
Underwriters' Laboratories Retardant 3187-2, dated 1/24/50
1" gypsum-perlite plaster1, u, over self-furring metal lath wrapped around column.
Y " gypsum-sanded plaster12, 1:3 mix on metal lath.
1' Portland-cement plaster12, 1:2 )4 mix on metal lath.
2-hours
1-hour 1-hour
Underwriters' Laboratories Retardant 3187-4, 5, 7
BMS-92, Table 40
STEEL BEAMS, GIRDERS & TRUSSES
CAST IRON 1H" Portland cement plaster12, lr'/io:2M> cement, lime and sand COLUMNS mix (by volume) on Y" rib metal lath with J4" broken air space.
3-hours
TIMBER
1" portland-cement plaster12, on metal lath, applied over column and
COLUMNS over steel or cast iron cap, %' ah space.
2-hours
1" gypsum-vermiculite plaster1, n, over metal lath with at least a
2)4" air space between lath and protected structural members.
4-hours
Protected with
Suspended Ceilings
1' gypsum-perlite plaster3, u, over metal lath, with at least a 3' air space between lath and structural members. Plaster on back of lath
1" minimum on ceiling, 1)4' to 3" at beam.
Yi` gypsum-perlite plaster1, u, over metal lath with at least 3Y>"
air space between lath and structural member.7
%" gypsum-vermiculite plaster1, *, plus
vermiculite acoustical
plastic over metal lath with at least a 2)4" air space between lath
and structural members.
4-hours 4-hours 4-hours
1" sprayed asbestos fiber8, 1!, over metal lath with at least a 2" air space between lath and protected structural member. If beam extends below general ceiling level, rating is reduced to 2-hours.
3-hours
1" gypsum-vermiculite plaster1, 12, on metal lath.9
Protected with
Ceilings Furred or in Contact with Structural Steel
1" neat wood-fibered gypsum12, or j ' gypsum-vermiculite plaster1, 12, on metal lath.3
Y" gypsum-sanded plaster12, 1:2, 1:3 mix on metal lath.9
Y" poitland cement or gypsum-sanded plaster12, 1:2, 1:3 mix on
metal lath.9 Three lbs. asbestos fiber and 15 lbs. of lime added to each bag of Portland cement.
4-hours 3-hours 2-hours 1}^-hours
BMS-92, Table 38
Underwriters' Laboratories Retardant 2773, dated 1/20/47 Underwriters' Laboratories Retardant 2993 (Supplement), dated 11/18/49 Underwriters' Laboratories Retardant 3355, dated 4/30/51 Underwriters' Laboratories Retardant 2773, dated 11/29/50
Underwriters' Laboratories, Retardant 2923, dated 6/15/50
BMS-92, Table 43
V/f V
CONSTRUCTION
Floor: 2H" concrete on metal lath. Ceiling: 1* gypsum-vermiculite plaster1, 12, on metal lath.
Floor: Same as above. Ceiling: % ' gypsum-vermiculite plaster1, 12, or 1' neat wood-fibered gypsum plaster on metal lath.
Fire Resist ance
AUTHORITY
4-hours 3-hours
TRBM-44, Table 18
STEEL
CO JOIST cc O FLOORS
o (Using Ui Contact,
Furred or Suspended Ceilings)
Floor: 2H " perlite concrete.
Ceiling:
gypsum-perlite plaster1, n, over metal lath.
Floor: 2 " concrete on metal lath.
Ceiling: % ' gypsum-vermiculite plaster1, 12, or 1' neat wood-fibered
gypsum plaster, on metal lath.
Floor: 2H' concrete on metal lath. Ceiling: 1" sprayed asbestos fiber12, on metal lath.8
Floor: 2H* concrete on metal lath.
Ceiling:
gypsum-sanded plaster12, 1:2, 1:3 mix on metal lath.
Floor: 2H' concrete on metal lath. Ceiling: H " sprayed asbestos fiber12, on metal lath.8
3-hours
Underwriter^' Laboratories Retardant 3454-2
23'2-hours
23'6-hours
2-hours
TRBM-44, Table 18
Floor: 2 ' concrete on metal lath.
Ceiling:
sprayed asbestos fiber12, on metal lath.8
1 H-hours
Floor: 2 " concrete on metal lath. Ceiling: % " gypsum-sanded plaster12, 1:2, 1:3 mix, or % " Portland cement plaster12, 1:2, 1:3 mix with 15 lbs. hydrated lime and 3 lbs. asbestos fiber per bag of cement, on metal lath.
Floor: 2H' concrete (minimum thickness over cells). Ceiling: IVfj" gypsum-vermiculite plaster ', u, over metal lath.
Metal lath required to be at least 3M" from underside of cellular
steel panel. Metal lath furred around beams and plastered 1%" thick with same mix.
1 H-hours 4-hours
Tested by the National Bureau of Standards
Floor: 3J4" concrete (minimum thickness over cells). Ceiling: 1 " gypsum-perlite plaster2, u, over metal lath. Metal lath
attached directly to underside of floor panel. Beams plastered 1H * thick over face of lath with same mix.
4-hours
Underwriters' Laboratories Retardant 3789-1, dated 10/3/56
Floor: 2' concrete (minimum thickness over cells). Ceiling: H* gypsum-vermiculite plaster2, n, over metal lath. Metal lath required to be at least 2H' horn underside of cellular steel panel.
4-hours
Underwriters' Laboratories Retardant 2689,
dated 12/18/39
Floor: 2' perlite concrete (minimum thickness over cells). Ceiling: 1" gypsum-perlite plaster3, H, over metal lath. Metal lath required to be at least 3" from underside of floor panel and steel beams.
4-hours
Underwriters' Laboratories Retardant 2993, dated 12/9/48
Floor: 2' concrete (minimum thickness over cells). Ceiling: 1" gypsum-vermiculite plaster.1, 12, on metal lath. Metal lath required to be at least 2 ' from underside of floor panel.
4-hours
BMS-92, Table 45
CELLULAR STEEL FLOORS
Floor: 2H' concrete (minimum thickness over cells).
Ceiling:
gypsum-vermiculite plaster1, n, plus H" vermiculite
acoustic plastic over metal lath. Metal lath required to be at least
7H' from underside of floor panel.
Floor: 2H" concrete (minimum thickness over cells).
Ceiling: %" gypsum-perlite plaster1, 12, plus H" acoustical plaster
on metal lath. Metal lath required to be at least 7 H * from underside
of floor panel and 2 ' from steel beams.
Floor: 2' concrete (minimum thickness over cells). Ceiling: 1' neat wood-fibered gypsum plaster12, on metal lath. Metal lath to be at least 9* from underside of floor panel. With lath not closer than 2', rating is 3-hours.
Floor: 2' concrete (minimum thickness over cells). Ceiling: 1H* sprayed fiber8, u, over metal lath. Metal lath required to be at least 4H ' from underside of panel.
Floor: 2' concrete (minimum thickness over cells). Ceiling: H' gypsum-perlite plaster1, 11, over metal lath. Space from lath to floor at least 15H*i and from lath to beams 3H'- (See 7)
Floor: 2" concrete (minimum thickness over cells). Ceiling: % " gypsum-perlite mill-mixed plaster n, over metal lath. Metal lath required to be at least 15 H ' from the underside of cel
lular steel panel and 3H" from steel beam. Beam rated 4 hours. (See13)
4-hours
Underwriters' Laboratories Retardant 2773, dated 11/29/50
4-hours
Tested by the National Bureau of Standards
4-hours BMS-92, Table 45
4-hours
Underwriters' Laboratories Retardant 3431-1, dated 9/14/51
4-hours
Underwriters' Laboratories Retardant 3355, dated 4/30/51
3-hours
Underwriters' Laboratories Retardants 3574-6, 3789, dated 7/25/57
OOBS
Floor: 2r concrete (minimum thickness over cells). Ceiling: H" gypsum-vermiculite plaster1, n, over metal lath. Space from lath to floor at least 15H', and from lath to beams 3H'- (See 6)
3-hours
Underwriters' Laboratories Retardant 2689, dated 12/13/49
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cc
O CONCRETE
O --1 JOISTS Uh
CONSTRUCTION
Floor: 3' concrete slab10. Ceiling: 1" gypsum-vermiculite plaster1, u, over metal lath. Metal lath required to be at least 8)4" from underside of floor joists.
Floor: 2" concrete slab10. Ceiling: %' gypsum-vermiculite plaster1, ", over metal lath. Metal lath required to be at least 8)4" tom underside of floor joists.
Fire Resist ance
AUTHORITY
4-hours
Underwriters' Laboratories Re tardant 3390-13, dated 11/12/54
3-hours
Underwriters' Laboratories Re tardant 3390-11, dated 1/19/54
cn
cc
o
CORRUGATED
o STEEL
H FORMS
Floor: 3)4" reinforced sand-gravel concrete over top of corrugations. Ceiling: 1" gypsum-vermiculite plaster1, ", over metal lath. Ceiling suspended at least 14)4 * below steel forms and 2y<i below steel beams.
Floor: 3J4" reinforced expanded-slag concrete over top of corrugallons. Ceiling: Metal lath attached directly to bottom of corrugated form. Self-furring metal lath wrapped around steel beams. Gypsum-per lite plaster, 100 lbs.: 2 cu. ft. mix, applied so as to fill corrugation
above lath and z/% below face of lath. Beams plastered 1)4" thick
over face of lath with same mix.
4-hours 4-hours
Underwriters' Laboratories Retardant 3413-1, dated 3/7/52
Underwriters' Laboratories Retardant 3413-4
Floor Assembly
Ceiling Assembly of Metal Lath and Plaster
Fire Resist ance
Authority
U1 WOOD
CC
O JOIST
O --i FLOORS u-i
% ' gypsum-sanded plaster12,1:2,1:3 mix. Metal lath attached with 1)4 U-gage, 7M" head, barbed roofing nails, at 6" c/c.
l-hour Combustible
Double wood floor (54'
sheathing, T. & G. finish, with asbestos paper be tween) supported on 2' x 10' joists. Ordinary buildincr DaDer can be
used with T. & G. sub-
flooring.
% ' Portland cement plaster12,1:2, 1:3 mix
with 15 lbs. hydrated lime and 3 lbs. as bestos fiber per bag of cement. Metal
lath attached with 1)4', 11-gauge, 7Ai"
head, barbed roofing nails, at 6" c/c.
Either of above 1-hour assemblies with additional supports for lath placed 27' c/c attached to alternate joists, consist ing of 1 loop of No. 18 wire slipped over
each of 2 nails driven in 1)4", 2' above
bottom on each side of joists, and ends of this loop tied below lath.
Combustible
1 H-hours Combustible
BMS-92, Table 42
Studs
2' x 4' Non-load bearing
WOOD
cn
sz:
STUD
O H HOLLOW
H
CO<Cn PARTI-
TIONS
2'x4* Load Bearing
2'x 2" Non-load bearing
%" gypsum-vermiculite plaster1, 12, on metal lath attached with 1)4', 11-gauge,
14' head, barbed roofing nails, at 5" c/c.
)4 gypsum-perlite plaster1, 1J, on metal lath attached with 1)4", 11-gauge, 14b"
head, barbed roofing nails, at 5" c/c.
lJi-hours Combustible
1 J^-hourB Combustible
Tested by the National Bureau of Standards
Total Thickness
Plaster Both Sides on Metal Lath
5 *A"
1' neat wood-fibered gypsum12
Fire Resist ance
2-hours Combustible
Authority
5? k k
to to CO
SVb" 5 %' s ys"
5 %"
%" gypsum-sanded12, 1:2, 1:2 mix with
mineral wool fill J4' gypsum-sanded12, 1:2, 1:3 mix
)4" Portland cement and sand12, 1:2, i:3 mix. Add 3 lbs. asbestos fiber per bag of cement. %" gypsum-sanded 12, 1:2, 1:2 mix
%' gypsum-vermiculite1,11
%' gypsum-sanded11, 1:1)4, 1:3 mix
)4" gypsum-sanded11, 1:1)4, 1:3 mix
1 H-hours Combustible
1-hour Combustible
1-hour Combustible
BMS-92, Table 30
Combustible
1-hour
Underwriters' Laboratories
Combustible Retardant 2773, dated 8/31/44
1-hour Combustible
1-hour Combustible
Underwriters' Laboratories Retardant 1355, dated 8/10/22
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STEEL
CO
STUD o
H P
HOLLOW
CC
<0-i PARTI
1 TIONS
1 SOLID
CO
2
PARTI
o
H TIONS
H
CC
<O-i
(Non-load bearing)
STEEL
ROOF
O-i
o DECK
CC ASSEM
BLIES
Studs
Total Thickness
Plaster Both Sides on Metal Lath
1" gypsum-perlite plaster l, ll, over metal lath attached to 14 * pencil rods on metal clips.
1" neat wood-hbered gypsum12
Y ' channels
or Pre fabricated Steel Studs (non-load bearing)
May vary, but mini mum air space of 2 ' is re
quired
between
interior
faces of
metal
lath
Prefabri cated Load Bearing Steel Studs
1" gypsum-perlite1, 11
A " neat wood-hbered gypsum12 Y" neat wood-hbered gypsum12 7A" gypsum-sanded12, 1:2, 1:3 mix Y" portland cement12, 1:2, 1:3 with 3 lbs.
of asbestos hber per bag of cement
Y" gypsum-sanded12, 1:2, 1:2 mix
1' neat wood-hbered gypsum12
%' neat wood-hbered gypsum12
Y" gypsum-sanded12, 1:2, 1:2 mix H" gypsum-sanded12, 1:2, 1:3 mix
Studs
Total Thickness
Thickness and Type of Plaster on Metal Lath
2H' 2 H'
2)4' neat wood-hbered gypsum 2lA' gypsum-perlite1
H' channels
2H' 2' 2'
2H' gypsum-vermiculite1 2' neat wood-hbered gypsum 2" gypsum-sanded 1:2, 1:2 mix
1H'
VA" gypsum-perlite2
Studless
2' 2' gypsum-sanded, 1:2, 1:2 mix
Roof4
2" vermiculite concrete
1' insulation board of shredded wood bonded with Portland cement.
1' insulation board of felted glass fiber.
1H' wood Hberboard insulation.
Suspended Ceilings of Metal Lath and Plaster 1' gypsum-vermiculite plaster2, 12
1" gypsum-vermiculite plaster2, 12
1' gypsum-vermiculite plaster2, 12
1" gypsum-sanded plaster12, 1:2 mix
1 H' wood fiber and ce ment binder.
1' wood hberboard in sulation.
Yi" gypsum-sanded plaster12, 1:2 mix
Y ' gypsum-sanded plaster12,1:2,1:3 mix
Fire Resist ance
3 H-hours
Authority
Ohio State University Test No. T-799
2 H-hours 2-hours 2-hours 1 J^-hours 1-hour 1-hour
BMS-92, Table 31 University of California Laboratory Tests of 1-48 and 4-51
BMS-92, Table 31
1-hour 2-hours5 1 H-hours
1-hour 1-hour
BMS-92, Table 27
Fire Resist ance
2H-hours 2-hours
2-hours 2-hours 1-hour
1-hour
1-hour
Fire Resist ance
4-hours
Authority
BMS-92, Table 32
Underwriters' Laboratories Retardant 3453, dated 2/13/52
National Bureau of Standards
National Bureau of Standards
Ohio State University, Test No. 129
Ohio State University, Test No. 147
Ohio State University, Test No. 162
Authority
3-hours 2-hours 2-hour8
Tested by the National Bureau of Standards
2-hours 1 H-hours
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NOTE:
Many of these fire resistive ratings, especially those for cellular steel floors, actually exceeded the fire-resistive period shown. They are listed as 1, Wi, 2, 21 i>, 3, and 4 hour assemblies to facilitate use of the data in conjunction with building code regulations.
Gypsum-sanded or Portland cement plaster mixed 1:2, 1:2 means 1 part neat to 2 parts sand aggregate by weight for both scratch and brown coats.
1. Scratch coat: 100 lbs. gypsum to 2 cu. ft. of aggregate. Brown coat: 100 lbs. gypsum to 3 cu. ft. of aggregate.
2. 100 lbs. gypsum to 2^ cu. ft. of aggregate for both scratch and brown coats. 3. 100 lbs. gypsum to 3 cu. ft. of aggregate for both scratch and brown coats.
4. Equivalent insulation permissible.
5. 2H hr. rating if load does not exceed 5120 psi of stud area. 6. Tested with openings for noncombustible ducts, electrical outlets, and
pipes. Their permissible combined area did not exceed 100 sq. in. per 100 sq. ft. of ceiling area. No failure, but test arbitrarily discontinued at 3 hours. 7. Tested with openings for noncombustible ducts, electrical outlets, etc. Their permissible combined area did not exceed 100 sq. in. per 100 sq. ft. of ceiling area. No failure; test arbitrarily discontinued after 4 hours. 8. Sprayed fiber is a proprietary product, usually applied by contractor licensed by the manufacturer.
9. These ratings are based on tests in which light-rolled sections and open-web joists were protected with metal lath and plaster ceilings attached directly to the bottom flanges.
10. Add 2* to overall floor slab thickness where electrical raceways and junc tion boxes ate used.
11. Plaster thickness is measured from face of metal lath to finished plaster surface.
12. Plaster thickness is measured from back plane.oLmetal lath, exclusive of ribs
to finished plaster surface.
^
13. Tested with openings for noncombustible/ ducts not exceeding 113 sq. in. per 100 sq. ft., and one electrical outlet not exceeding each 90 sq. ft., of ceiling area.
Authorities cited are:
BMS-92: National Bureau of Standards, Building Materials and Structures Report No. 92.
TRBM-44: National Bureau of Standards, Technical Report on Building Materials No. 44.
Values attributed to NBS are derived from unpublished NBS test reports.
Additional information or details of construction available upon request.
Printed in U.S.A.
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