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Building Design and Construction Handbook - Merritt - Ventech!

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TABLE 11.9 Limiting Spans for Metal Lath, in<br />

WALL, FLOOR, AND CEILING SYSTEMS 11.57<br />

High-rib exp<strong>and</strong>ed-metal lath is used when greater rigidity is desired, for example,<br />

for spacing supports up to 24 in c to c <strong>and</strong> for solid, studless plaster partitions.<br />

The lath has a herringbone mesh pattern <strong>and</strong> V-shaped ribs running the<br />

length of each sheet. For 3 ⁄8-in rib lath, 3 ⁄8-in-deep ribs are spaced 4 1 ⁄2 in c to c,<br />

alternating with inverted 3 ⁄16-in ribs. For 3 ⁄4-in rib lath, 3 ⁄4-in-deep ribs are spaced<br />

6 in c to c. This type of high-rib lath may be used as a form <strong>and</strong> reinforcement for<br />

concrete slabs, but its thickness makes it generally unsuitable for plaster construction.<br />

The 3 ⁄8-in rib lath may also be used as a concrete form, but its rigidity makes<br />

it unsuitable for contour lathing.<br />

Welded-wire lath should be made of wire 16 ga or thicker, forming 2 � 2-in<br />

or smaller meshes, stiffened continuously parallel to the long dimension of the sheet<br />

at intervals not exceeding 6 in. The paper backing should comply with Federal<br />

Specifications UU-B-790, ‘‘<strong>Building</strong> Paper, Vegetable Fiber (Kraft, Waterproofed,<br />

Water Repellant, <strong>and</strong> Fire Resistant).’’ Acting as a base to which plaster can adhere<br />

while hardening about the wire, the backing should permit full embedment in at<br />

least 1 ⁄8 in of plaster of more than half the total length <strong>and</strong> weight of the wires.<br />

Table 11.9 lists limiting spans for various types <strong>and</strong> weights of metal lath for<br />

ceilings <strong>and</strong> walls.<br />

Tying <strong>and</strong> Nailing. Installation of metal lath should meet the requirements of<br />

ASTM C841. Attachments of metal lath to supports should not be spaced farther<br />

apart than 6 in along the supports.<br />

When metal framing or furring is used, metal lath should be tied to it with 18ga,<br />

or heavier, galvanized soft-annealed wire. Rib lath, however, should be attached<br />

to open-web steel joists with single loops of 16-ga, or heavier, wire, or double<br />

Type of lath<br />

Min wt.,<br />

lb/yd 2 Wood<br />

Vertical supports<br />

Metal<br />

Solid<br />

partitions* Other<br />

Horizontal<br />

supports<br />

Wood or<br />

concrete Metal<br />

Diamond mesh (flat 2.5 16 16 12 12 12<br />

exp<strong>and</strong>ed) metal lath 3.4 16 16 16 16 13 1 ⁄2<br />

Flat- ( 1 ⁄8-in) rib exp<strong>and</strong>ed 2.75 16 16 16 16 16<br />

metal lath 3.4 19 24 19 19 19<br />

3 ⁄8-in rib exp<strong>and</strong>ed metal lath† 3.4 24 24† 24 24 24<br />

4.0 24 24§ 24 24 24<br />

3 ⁄4-in rib exp<strong>and</strong>ed metal lath 5.4 † 24 36‡ 36‡<br />

Sheet-metal lath† 4.5 24 † 24 24 24<br />

Welded-wire lath 1.16§ 16 16 16 16 16<br />

1.95� 24 24 24 24 24<br />

* For paper-backed lath, only absorbent, perforated, or slotted paper separator should be used.<br />

† Permitted for studless solid partitions.<br />

‡ Permitted only for contact or furred ceilings.<br />

§ Welded 16-ga wire, paper-backed lath.<br />

� Paper-backed lath with welded wire, face wires 16 ga, every third back wire parallel to line dimension<br />

of lath 11 ga.<br />

Source: Based on ‘‘Uniform <strong>Building</strong> Code,’’ International Conference of <strong>Building</strong> Officials, Inc.

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