What a tie wire actually does

A wire tie holds a bar where the detailer put it until the concrete sets. That is the whole job. Ties are not counted in the structural design, so heavier wire does not make a slab stronger, and they do not set cover either: chairs and bolsters do that. What a good tie does is stop the mat rolling, sliding or lifting while a crew walks it, a pump hose drags over it and wet concrete pushes at it. So buy for three things: holding power that survives the pour, softness that twists fast and stays twisted, and a delivered cost per foot low enough that nobody starts rationing wire.

Gauge: which size for which job

Tie wire is sized by steel wire gauge, the Washburn and Moen system the wire trade uses, not the AWG numbers used for electrical conductors. Lower number means thicker wire.

GaugeDiameterWhere it fits #9 to #110.1205 to 0.1483 inScaffolding, heavy bundling, tie off. Not a hand tie wire for bar. #120.1055 inHanger and support wire. Too stiff to twist around bar by hand. #160.0625 inThe default for rebar. Best balance of holding power and twist. #180.0475 inLight mats, mesh, residential slabs, high tie counts. #200.0348 inLight bundling, mesh, decorative and display work.

For structural rebar, #16 is the working default and what the trade generally means by rebar tie wire. You will also see 16.5 gauge sold for the same job: slightly thinner, faster for some crews, but do not swap it in where a drawing calls out 16 gauge. Drop to #18 only where bars are small and tie counts are high, and keep it off vertical cages, because what it saves in hand force it gives up in holding power.

Do not reach for a thicker gauge to fix a weak tie. The fix is a better knot. Snap ties suit flat mats on the ground. Walls, columns and cages want a wrap and snap or a saddle, because a snap tie on a vertical bar can slide. A figure eight resists rotation best and costs the most wire and time. Most jobs run #16 annealed tie wire in the 3.5 lb coil and vary the knot by location.

Black annealed, galvanized or stainless

Black annealed is heat treated dead soft. It twists tight with little effort, stays put, and is the cheapest per foot. It has no coating and surface rusts quickly outdoors, which is fine for steel about to be buried where cover does the protecting. Our black annealed listings state ASTM A853, the specification for carbon steel wire for general use.

Galvanized is the same steel with a zinc coat. It is stiffer and springier, so it fights you on the twist, and it resists rust before and after the pour. Pay for it when the steel will sit exposed for weeks, in humid or coastal air, or where the wire stays visible in the finished work. On light mesh and mat work that has to weather, #18 galvanized annealed tie wire in the 3.5 lb coil is the usual pick, and that listing states ASTM A641 for zinc coated carbon steel wire. If your submittal needs a mill certificate, ask before you order.

Stainless is expensive, and there are two good reasons to buy it: the reinforcement itself is stainless, or the tie faces an exposure no coating will survive. The #16 tie wire 1 lb coil lists black annealed, galvanized and stainless as selectable finishes, so it is the cheapest way to get a small quantity.

The coated bar exception

If the drawings call for epoxy coated bar, bare steel tie wire is usually not permitted. Standard practice is to tie it with plastic coated or epoxy coated wire, so the twist does not cut the coating and start a corrosion cell, and to use coated or plastic tipped supports. Read the reinforcement section of your specification first, because requirements vary by agency and an inspector will catch a substitution. We do not list a coated tie wire, so plan that item with your rebar supplier.

How much wire the job takes

#16 runs roughly 90 to 100 feet per pound, and you can read it off the packs: the 1 lb coil is about 100 ft, the 3.5 lb coil 340 ft, the 5 lb plastic spool about 480 ft, the 5 lb metal spool about 450 ft. Those lengths are approximate, because tie wire is cut to weight and not to length. Thinner wire buys more length per pound: the #20 galvanized half pound coil holds about 155 ft, near 310 ft per pound, and the #18 galvanized 3.5 lb coil is listed at about 580 ft, near 166 ft per pound.

Wire per tie depends on bar size and knot, and the spread between a tight snap tie on small bar and a saddle on heavy bar is too wide for one number. On a large order, cut a dozen ties the way your crew ties them and measure the offcuts. For planning, assume 12 inches per tie on #16: at one foot per tie the footage below is also roughly the tie count, so a pound is about 100 ties.

PackListed lengthDelivered pricePer lbPer 100 ft #16, 1 lb coil100 ft$11.65$11.65$11.65 #16, 3.5 lb coil340 ft$16.49$4.71$4.85 #16, 5 lb plastic spoolabout 480 ft$33.92$6.78$7.07 #16, 5 lb metal spoolabout 450 ft$34.82$6.96$7.74 #18 galvanized, 3.5 lb coilabout 580 ft$35.06$10.02$6.04 #20 galvanized, 1/2 lb coilabout 155 ft$6.19$12.38$3.99

Those are delivered prices, so each figure is landed cost with no freight to add, correct as listed at the time of writing.

Among the #16 packs the 3.5 lb coil is cheapest on both measures and the 1 lb coil far the dearest, so buy the small coil because it fits a tool bag, not because it is cheap. Less obviously, the #18 galvanized coil looks expensive at $10.02 per pound but carries about 580 ft, landing at $6.04 per 100 ft, cheaper per foot than either #16 spool. Cost per foot is the better comparison, but it only compares fairly between gauges that will both do the job: #20 is cheapest per foot here and has no business on a structural mat.

Count the intersections you will actually tie, not every crossing in the grid. You do not tie them all, and tying more adds no structural capacity. Flat slab work needs a fraction of crossings tied, walls and cages need more, and a mat that gets lifted needs its perimeter tied solid. The drawings and the specification govern the pattern, so settle it before you price the wire.

Coil or spool, and what feeds a tool

Pick the pack by how the wire gets to the tie, not by unit price alone. The 1 lb coil is tool bag and punch list size. The 3.5 lb coil is the workhorse: it fits a standard tie wire reel and most holders, and it is a sensible weight on the hip all day.

• 5 lb spool. A spool pays out without collapsing into itself, which is what a bag mounted or bucket dispenser needs. The plastic spool is listed longer and is cheaper per foot, so take the #16 black annealed 5 lb metal spool when you want one that survives a truck bed and can be reloaded.
• 100 lb coil. A cutting station, not a hip load, and read the gauge carefully. Black annealed scaffolding tie wire in 100 lb coils is offered in #9 through #12: heavy wire for scaffolding, tie off and bundling, not a bulk source of #16 rebar tie wire, and too stiff to twist around bar by hand. The listing gives a weight and not a footage, so ask if you need a length.

Battery powered rebar tying tools do not run on bulk hand tie wire. They feed from the tool maker's own pre wound reels, ordinary 16 and 16.5 gauge hand tie wire will not run in them, and reels are often not interchangeable even between tool families from one maker. Buy tool wire from the tool maker and check the model.

Two checks before the pour

Walk the mat during placement and check two things at each crossing you pass. If you can rock the bar by hand, the tie is loose, and a loose tie is the usual reason a mat moves. If the wire has snapped or the bar has been pulled out of line, the tie was over twisted: twist tight against both bars, then stop. Fixing one crossing takes seconds. Fixing bar after the concrete sets does not.

How to buy without overpaying

• Compare delivered cost per foot. Divide price by listed length, not by coil weight.
• Standardize one gauge for the job, or the wrong coil ends up on the wrong pour.
• Buy volume as volume. For pallet quantities send a quote request rather than adding coils to a cart one at a time. Browse the full tie wire range by gauge and pack size to see what is stocked first.

For most rebar work the answer is simple. Run #16 black annealed in 3.5 lb coils, move up to spools if your crew uses bag dispensers, keep one small coil on the truck, and pay for galvanized or stainless only when the exposure or the specification calls for it.