How to Specify

A common misconception among architects and structural engineers is that Welded Wire Reinforcing (WWR) is what you buy at a hardware store – small, flimsy wire mesh. While WWR does come in these smaller formats, those are not the durable, construction-grade materials used in structural applications. Ivy Steel & Wire manufactures WWR sheets with wire diameters up to 3/4” (equivalent in diameter to a #6 rebar).

VARIGRID – A Step Beyond Traditional Welded Wire Mesh

VARIGRID – a step beyond traditional welded wire mesh – lives up to exactly what its name implies: the spacing or grid of the welded wire, its size, length, and width of the sheet or roll can be varied to meet the needs of the professional designer.

Thus, only the reinforcement necessary for proper distribution of steel in the concrete plus the ease of placement serve to reduce costs and at the same time speed construction.

Welded Wire Mesh - Structural Mesh

In developing VARIGRID™, Ivy Steel & Wire retained the quality characteristics inherent in the proven performance of welded wire mesh, a “premeshated” reinforcement consisting of high strength wires welded perpendicular to each other in a square or rectangular pattern.  The steel wire – cold drawn from hot rolled, low carbon steel rod is automatically welded into a rigid pattern through a process called resistance welding.  Resistance welding combines pressure and electrical heat to fuse with wires.

Machine Resistance Welding – Pressure and heat fuse the intersecting wires into a homogeneous section and fix all wires in their proper position.

Welded wire mesh – including VARIGRID – may consist of either smooth wires, deformed wires, or a combination of the two.  Deformations are formed by indenting a pattern into the wire. The size and spacing of the indentions are covered by the specifications of the AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) which also govern all the other properties of the welded wire mesh.

SPECIFICATIONS COVERING WELDED WIRE MESH

• ASTM A82 Cold–Drawn Steel Wire for concrete reinforcement.
• ASTM A185 Welded Wire Mesh for concrete reinforcing.
• ASTM A496 Deformed Steel Wire for concrete reinforcing.
• ASTM A497 Welded Deformed Steel Wire Mesh for concrete reinforcement.

These ASTM specifications cover the physical properties of the wire and wire mesh and describe the testing procedures the manufacturer is required to perform.  In addition to these ASTM specifications, there are other sets of rules which apply to the use of the mesh in design applications.

In the American Concrete Institute’s ACI Building Code, the designer will find such rules of use as the design yield, spacing of wires, how to bend the mesh, and what kind of laps are required in structural applications in buildings.            

PAVING SPECIFICATIONS

The American Association of State Highway and Transportation Officials (AASHTO) provides welded wire design formulae for highways, streets, precast concrete pipe, concrete underground structures, and box culverts.  The Federal Aviation Authority (FAA) is the source for airport paving including runways and ramps where welded wire mesh is extensively specified.

SPECIFY ANY VARIETY OF WIRE SPACINGS.

Wires can be spaced closer than standard or as far apart as the designer desires.  Spacing can also vary from one part of the sheet or roll to another.  VARIGRID spacing can be accomplished in both directions – transversely and longitudinally.

SPECIFY EXACT SHEET DIMENSIONS OR ROLL WIDTHS.

For example, if standard sheet sizes leave scrap but sheets that are 7 ft. 3 in. by 26 ft. 4 in. (2.21 m x 8.05 m) will fit the job exactly – that’s your spec.  With VARIGRID, you can specify whatever sheet size you need or if the mesh is more convenient in rolls, simply order it that way.  Specify the width you will use and save cutting off the excess.

TO OVERHANG OR NOT TO OVERHANG.

VARIGRID versatility abounds when detailing overhangs which can be as long or as short as necessary.  Or, there may be no overhangs at all…even different overhangs on different sides of the sheet or roll.  You can really design VARIGRID your way.

HOW TO ORDER STANDARD WELDED WIRE

Here are some helpful hints on how to order standard welded wire mesh, but please note that an order for VARIGRID can involve many variables because of VARIGRID’s versatility.  However, as with nearly every industry, wire has its own language or terminology which aids substantially in obtaining the proper mesh for your project.  Wire mesh is available in sheets or rolls.  That’s the starting point.

WIRE SIZES – The size of the wire is given as a W number or a D number.  W denotes a smooth wire and D means deformed.  The number that follows the letter is the area of the wire in hundredths of a square inch.  For instance, a W10.2 wire would be a smooth wire with a cross sectional area of 0.102 square inches while a D7.4 would indicate a deformed wire with a cross sectional area of 0.074 square inches.  (It should be noted that wire can be drawn to the exact area required which eliminates “oversteeling” and excessive costs.)

Wire sizes were previously designated by American Standard “Wire Gage Numbers,” but unfortunately there is no direct correlation between gage and “W” numbers.  Thus, through calculations it is determined that “6” gage wire is equivalent to W2.9 wire.  A table that compares the two numbering systems is available from the Wire Reinforcement Institute or from an Ivy Steel & Wire Company representative.

STYLE – Spacings and sizes of wire in standard welded wire mesh are identified by “Style”.  A typical designation is 6x12 W16xW8.  This code denotes a welded wire mesh in which:

Spacing of longitudinal wires = 6”
Spacing of transverse wires = 12”
Size of longitudinal wires = W16 (0.16 sq. in.)
Size of transverse wires = W8 (0.08 sq. in.)

NOTE – Style gives spacing and wire sizes only and does not show any other information such as width and length of sheet or roll.

It is also very important to note that “longitudinal” or “transverse” wires are related to the manufacturing process whether for standard wire mesh or VARIGRID.  The terms have no reference to the position of the wires in a concrete structure.

DIMENSIONS – Linear measurements, other than wire spacing included in the style designation, are as follows:

• WIDTH = Center to center distance between outside longitudinal wires.
  
  
• SIDE OVERHANG = Extension of transverse wire beyond centerline of outside longitudinal wires.  When specific lengths of side overhang are needed, the length required on each side shall be given in inches.  [Example:  (+1” +3”) means 1” overhang on one side, 3” on the other.]
  
  
• OVERALL WIDTH = Width plus side overhangs.  In other words, tip-to-tip of transverse wires.
  
  
• LENGTH = Tip-to-tip dimension of longitudinal wires.  The length dimensions always include end overhangs.
  
  
• END OVERHANGS = Extension of longitudinal wires beyond centerline of outside transverse wires.  Standard end overhangs are a dimension equal to ½ the transverse wire spacing.  Unless otherwise noted, standard end overhangs are assumed to be required and no end overhang dimensions need be specified.

TYPICAL MESH ORDER

The following example of welded wire mesh items illustrates how a typical order using the nomenclature described might appear:

HOW TO SPECIFY VARIGRID

Because of the variable in wire layout, contact your Ivy Steel & Wire representative and describe your steel requirements or send drawings to Ivy Steel & Wire VARIGRID™ detail sheets can be prepared and returned for your approval.