Simpson Coil Straps Explained: LSTA, MSTA, and CS Series Guide

If you've never had a building inspector stop you mid-frame to ask about your strap spacing, consider yourself lucky. If you have, you already know that coil straps aren't optional hardware on a lot of builds. In wind and seismic zones especially, the strapping between your wall plates, your sheathing connections, and your hold-down system is exactly what keeps a framed wall from racking under lateral load.

Simpson Strong-Tie makes three main families of coil straps: the LSTA light strap, the MSTA and MSTC and MSTI medium straps, and the CS and CMST heavy-duty coil straps. They're not the same thing. They have different gauges, different load ratings, different applications, and some are designed specifically for shear wall assemblies and high-wind zones.

This guide covers all three families, what's different between them, where each one goes, how to install them correctly, and every model TotalFastening.com carries.

A standard wood frame wall does well under vertical loads. It's the lateral forces that cause problems. Wind blowing against the face of a building, or seismic movement shaking a foundation, both push and pull the wall frame in ways that gravity alone doesn't resist. If your wall system doesn't have adequate tension straps at the top and bottom plates, and at floor-to-floor transitions, the framing can separate at those connections when the load hits.

The Insurance Institute for Business and Home Safety (IBHS) ran controlled experiments putting residential framing under simulated hurricane-force winds. What they found was consistent: houses without engineered connection hardware at the top and bottom of wall panels, and at roof-to-wall connections, sustained significantly more structural damage at lower wind speeds than houses with proper metal connector hardware installed throughout.

That's not a theoretical exercise. The same physics applies every time a severe storm rolls through. Simpson's coil straps are one part of a connected system that includes joist hangers, holdowns, and shear wall panels — and each component only works if the others are installed to spec alongside it.

Tim Uhler, a lead carpenter and contributing editor for the Journal of Light Construction, summed up the installation mindset this way in a July 2021 JLC article on framing connectors: "The strap goes where the load path goes. If you don't understand the load path, you're just nailing metal to wood." The load path starts at the roof, travels through the walls, and terminates at the foundation. Coil straps are the connectors that keep the path intact at the critical transition points.

A coil strap is a continuous roll of galvanized steel strap, cut to length on the job, nailed to structural framing members on both sides of a connection to provide tension resistance. They're not the same as a pre-punched strap connector like an H1 hurricane tie — those have fixed lengths and pre-determined nail patterns. Coil straps give you the flexibility to customize the strap length and nail count to meet the required load for the specific connection.

The nail holes are pre-punched at set spacing. You install the strap by wrapping it over the connection point, aligning the holes, and nailing off both sides. Nail size and count are critical — the published allowable load is based on a specific nail spec. Undershooting the nail count or using the wrong nail diameter means you're not getting the rated load out of the strap, even if it looks right on the wall.

Code compliance for Simpson coil straps falls under ICC-ES ESR-1799, which covers their allowable loads under the IRC and IBC. If you're on an inspected project, have that report number ready.

The LSTA is the most commonly used coil strap in residential framing. It's a 20-gauge, 1-1/4-inch-wide strap designed for standard wall framing connections — stud-to-plate, top-plate-to-top-plate, and similar tension connections that come up on a typical wood frame build.

The 20-gauge steel keeps the strap flat against the framing without requiring notching or plate routing. On most builds, you're nailing it into the face of the stud and plate with 10d or 16d nails through the pre-punched holes. Each hole accepts an 8d, 10d, or 16d depending on the specific load table you're working with.

LSTA straps come in two coating options: standard galvanized (ZMAX coated) and stainless steel for corrosive environments like coastal construction, treated-lumber assemblies, or pool enclosures. If you're working within 300 feet of salt water, the stainless steel models are worth considering over standard galvanized.

TotalFastening carries LSTA straps in coil form in two lengths — 50 feet and 150 feet — in both standard and stainless options.

The MSTA series steps up from the LSTA in gauge and design. There are three variants: the standard MSTA, the MSTC (which has a different hole pattern and is approved for certain connector-to-connector applications), and the MSTI (interior version with a narrower profile for tight framing situations).

Where the LSTA is a flat 20-gauge strap, the MSTA runs in 16-gauge and 18-gauge depending on the specific model, with a 1-1/4-inch or 2-inch width. The heavier gauge gives you higher allowable loads at the same nail count — useful in floor-to-floor strapping and wall assembly designs that need more tension capacity without going to a full-length holdown.

The MSTC is specifically designed for continuous-tie applications — where you need a strap to run from the sill plate on one story up through the double top plate and connect to the wall above. That continuous load path is a code requirement in high wind and seismic zones under the IRC and IBC, and the MSTC is one of the products listed for it.

The MSTI is a 14-inch fixed-length strap (not a coil) with a bent tab for installation inside the stud cavity or in tight spaces where you can't wrap a flat strap over the top of the connection. If you're dealing with platform-framed walls and you need to strap from a stud to the plate inside the cavity, the MSTI is what fits without sticking out past the framing face.

The CS and CMST straps are the heavy end of the coil strap family. Where the LSTA and MSTA are for standard framing connections, the CS series is built for shear wall assemblies, multi-story continuous tie systems, and connections that need significantly higher tension loads than a 20- or 18-gauge strap can provide.

The CS (coil strap) runs 16 gauge in a 1-1/4-inch width. The CMST (corrugated medium strap) uses a corrugated profile — the ridges across the face of the strap add stiffness, which reduces the tendency for a long strap run to bow away from the framing face before it's nailed off. That profile also gives a better bearing surface at each nail hole under tension load.

The CMST is one of the most common straps you'll see called out on a structural engineer's plan set for multi-story wood framing in wind and seismic zones. If your plan calls for a continuous tie from the foundation plate up through multiple stories, the CMST is often the specified product because its load capacity at standard nail counts meets the required design values without requiring uncommon fastener sizes.

Both the CS and CMST are available in coil form, and both are listed under ICC-ES ESR-1799 for allowable load values under the IRC and IBC.

This is where most installation errors happen. Getting the strap on the wall isn't complicated. Getting it installed to the rated load is where attention to detail matters.

If you're working from a structural engineer's plan, the required tension load is specified. If you're working from prescriptive code tables (IRC Tables R602.10 and R602.3.2 for braced wall connections), pull the required load from the table based on your wall height, braced panel spacing, and wind exposure category. That number tells you which strap family and nail count you need before you pull any strap off the coil.

Cut the strap at a nail hole — never between holes. You lose bearing area at the cut end if it's not at a hole. Position the strap centered on the connection point with equal nail engagement on both sides. On a top-plate connection, that means equal strap length above and below the plate. On a floor-to-floor transition, the strap should bridge the rim joist or band joist entirely and bear on the stud or plate above and below.

This is the part that makes or breaks the connection. The nail size and count listed in the load table are not suggestions. Each hole accepts a specific nail diameter — typically 10d x 1-1/2" or 10d x 1-3/4" depending on the strap model — and the published load value assumes every hole in the strap is filled on both sides. If you skip holes to save nails, you're reducing the rated capacity by a proportional amount.

For LSTA and MSTA straps, a framing nailer with 10d nails is the fastest tool for nailing off on production framing. For CS and CMST straps where the nail spacing is tighter, a palm nailer or a positive-placement nailer gives you better control on the nail angle. Angled nails through a strap hole reduce the effective bearing area and can cause the strap to pull through the hole under load instead of transferring load to the wood fibers.

A strap that's twisted, bowed, or bridging an air gap between the strap and the framing face isn't making full contact. Under tension load, the strap will try to straighten before it transfers force to the fasteners — that initial movement isn't rated in the load tables and introduces slack into the connection. Keep the strap flat and tight against the wood as you nail. The corrugated profile of the CMST helps here since the ridges lock the strap against the face of the stud or plate as it seats.

Stud-to-plate connections at the top and bottom of walls, top plate laps at corners, and connections at the first floor bearing point on a balloon or platform frame. The LSTA is your everyday general framing strap — low gauge, easy to cut and nail, and code-listed for standard residential loads.

Floor-to-floor strapping in platform frame construction, top plate connections in braced wall panels, and anywhere a plan set calls for a "continuous tie" from one story to another. The MSTC bridges the rim joist or band joist and connects the wall framing above and below it without interruption in the load path.

Engineer-specified shear wall chord strapping, boundary member connections in a wood structural panel (WSP) shear wall, and multi-story continuous tie systems in SDC C and above (Seismic Design Category). 

When a structural engineer specifies coil strap by model on the plans, it's usually the CMST because of its higher gauge and corrugated profile. Don't substitute a LSTA for a CMST because you ran out of the right material — the load values are different and the inspection will catch it.

Standard LSTA, MSTA, and CS straps come with ZMAX galvanized coating — Simpson's heavier-than-standard zinc coating that's approved for use with ACQ and CA-C treated lumber. If your plates or studs are treated, the ZMAX coating is what you need. A standard zinc-plated strap on treated lumber will corrode faster than the connection should last.

For coastal projects — generally anything within the high-humidity, salt-air zone — the Type 316 stainless steel variants (LSTA-SS, MSTC-SS, CS-SS, CMST-SS) are available in the TotalFastening catalog. These are the same strap designs, same gauges, same hole patterns, just in 316 SS for maximum corrosion resistance. They cost more. They also don't corrode through in 10 years on a beach house.

• Coil strap cutter or heavy-duty tin snips — never use a grinder or torch; the heat affects the zinc coating at the cut edge
•  Framing nailer (21-degree or 30-degree coil) with 10d x 1-1/2" or 10d x 1-3/4" nails — check the strap's load table for the nail spec
• Palm nailer or positive-placement nailer — for CS and CMST straps in tight spaces or where nail angle control matters
• Tape measure and pencil — cut at a hole, not between holes
• Simpson's Connector Selector app or the printed catalog — for looking up allowable loads by nail count when you're sizing a connection in the field