For decades, builders have relied on galvanized expanded-metal lath to create a mechanical bond between stucco or manufactured-stone veneer and the building substrate. But anyone who has handled those large, sharp metal sheets knows the process comes with real drawbacks. The material rusts over time, cuts up hands and arms during installation, and every fastener penetration through the housewrap creates a potential water entry point. A newer alternative made from alkaline-resistant fiberglass solves all these problems while delivering equal or better strength. Fiberglass lath, sold under brand names like SpiderLath, is changing how experienced contractors approach exterior cladding. Understanding the differences between these materials helps builders make informed decisions that affect both installation speed and long-term durability, much like choosing between residential heating systems where the right choice depends on the specific application.
The Practical Problems with Traditional Metal Lath
Standard galvanized expanded-metal lath comes in large sheets that are notoriously difficult to handle on a job site. Each sheet has razor-sharp edges that can cause significant cuts, and experienced crews learn to work around these hazards rather than eliminating them. The weight alone makes overhead and vertical installation exhausting. A single sheet of metal lath is heavy enough that working on tall walls or chimneys requires multiple trips up and down the ladder, each time hauling awkward, sharp material.
Beyond the handling issues, metal lath has a fundamental durability problem. Even galvanized steel eventually rusts when exposed to moisture, and the tiny holes created by fasteners through housewrap or felt paper compromise the building envelope. Over years of service, rust stains can bleed through stucco finishes, and corroded lath loses its structural integrity. These are not theoretical concerns. Builders who have torn out old stucco jobs know that the metal lath behind failed installations is often rusted to the point of crumbling. The search for better alternatives has led many professionals to explore precision construction tools and materials that offer both performance improvements and easier handling.
- Metal lath sheets are heavy and awkward to carry up ladders or scaffolding.
- Sharp edges cause hand and arm injuries during routine installation work.
- Galvanized coating eventually fails, leading to rust and structural weakness.
- Every staple or nail penetration through housewrap creates a moisture path.
- Damaged sheets that sit on site become unusable crinkled scrap metal.
How Fiberglass Lath Eliminates Rust and Simplifies Handling
Fiberglass lath addresses every pain point associated with metal. The material ships in rolls rather than flat sheets. A typical 4-foot by 75-foot roll weighs only about 25 pounds, which means one person can carry enough material to cover an entire wall in a single trip. When working on tall structures like chimneys, a contractor can climb to the top, unroll a 4-foot by 25-foot section that weighs around 7 pounds, fasten it at the ridge, and work downward. There is no wrestling with heavy sheets and no risk of cutting arms on sharp edges. The comparison is similar to why builders now prefer plastic PEX fittings over traditional metal plumbing connections in many applications.
The material is made from alkaline-resistant fiberglass that is coated to provide stiffness and protect the glass fibers from the abrasive elements in stucco mixes and stone adhesives. Despite being rigid enough to lie flat against a wall, fiberglass lath remains flexible enough to fold neatly around inside and outside corners without the need for special bending tools. On smaller decorative projects like interior stucco range hoods or fireplace surrounds, this workability saves significant time over cutting and shaping metal.
Fiberglass cannot rust. The material sits behind stucco finishes indefinitely without corroding, staining, or losing its mechanical properties. For foundations, exterior foam insulation covers, and below-grade applications, this rust resistance is especially valuable.
Built-In Furring Creates Better Mortar Bond
One of the most innovative features of fiberglass lath products like SpiderLath is the integrated foam-rubber furring system. These rubber strips run across the back of the lath at 6-inch intervals and serve two critical functions. First, they hold the lath away from the substrate, creating a gap that allows stucco mortar to squeeze through the mesh openings and lock around the strands from both sides. This mechanical lock is what gives stucco its holding power, and the consistent gap created by the furring strips ensures uniform coverage.
Second, and perhaps more importantly, the foam-rubber strips seal every staple and nail penetration through the felt paper or housewrap. When a fastener drives through the rubber strip and into the substrate, the foam compresses around the fastener shank, creating a water-resistant seal. This addresses one of the biggest weaknesses of metal lath installations, where every fastener hole remains an open pathway for moisture to reach the sheathing. The self-sealing property means the water-tightness of the building envelope is preserved even after hundreds of fasteners are installed. Builders working with fiberglass reinforced panels in other applications will recognize the same attention to moisture management that makes these materials effective in demanding environments.
| Feature | Metal Lath | Fiberglass Lath |
|---|---|---|
| Weight (per 100 sq ft) | Approx. 15-20 lbs | Approx. 8-10 lbs |
| Form factor | Flat sheets, 2×8 ft | Rolls, 4×75 ft |
| Cutting method | Metal snips / shears | Utility knife or scissors |
| Rust resistance | Poor (eventually corrodes) | Excellent (will not rust) |
| Sharp edges | Yes, hazardous | No, safe to handle |
| Furring system | Must be added separately | Built-in foam rubber |
| Fastener sealing | None | Self-sealing foam strips |
| Cost per sq ft | ~$0.45-$0.55 | ~$0.45-$0.50 |
Installation Methods and Best Practices
Installing fiberglass lath follows similar principles to metal lath but with some important differences that take advantage of the material properties. Like traditional lath, fiberglass lath requires mechanical fasteners spaced 6 inches on center along every stud or substrate. Galvanized roofing staples with a 1-inch crown and 1.25-inch leg length work well, as do standard roofing nails. The fasteners must penetrate the substrate by at least 3/4 inch to provide adequate holding power.
Because stucco expands and contracts at a different rate than the wall substrate, sealing all penetrations through the weather-resistant barrier is essential. Many contractors use a double layer of asphalt felt or a layer of housewrap like Tyvek beneath the lath. The foam-rubber furring strips should be oriented vertically to allow any incidental moisture to drain downward to the weep screed at the base of the wall. This drainage detail is critical for long-term performance and prevents trapped moisture from causing damage behind the stucco. Just as circular saw upgrades can dramatically improve cutting precision, proper lath orientation and fastening patterns make a measurable difference in the final stucco installation quality.
- Install housewrap or double-layer felt paper over the sheathing, with proper flashings at all openings.
- Roll out fiberglass lath horizontally or vertically depending on wall dimensions, overlapping seams by at least 2 inches.
- Fasten through the foam-rubber furring strips at 6 inches on center using roofing staples or nails.
- Orient the rubber strips vertically to promote drainage to the weep screed.
- Cut the lath with a utility knife or heavy scissors. Score and snap for straight cuts on large sections.
- Fold the material around inside and outside corners. No corner bending tools are required.
- Install galvanized or PVC corner bead, drip screed, and expansion joints on large wall areas.
On larger projects, using galvanized or PVC corner beads, drip screeds, and expansion joints at control joints is recommended. These pieces provide clean edges and accommodate movement in the stucco assembly. On smaller jobs like chimney enclosures or decorative interior work, these trim pieces can often be omitted.
Cost, Availability, and Job Site Durability
The cost of fiberglass lath is comparable to galvanized expanded-metal lath, working out to roughly $0.45 to $0.50 per square foot. A standard 300-square-foot roll retails for about $135, which puts it in the same price range as the metal equivalent. The main logistical difference is that fiberglass lath typically must be ordered directly from the manufacturer rather than picked up from a local lumberyard. This requires some advance planning, but the performance advantages make it worth the extra effort.
Job site durability is another area where fiberglass lath excels. Metal lath that sits on site for weeks before installation tends to get bent, crushed, and rusted into unusable scrap. Fiberglass lath, in contrast, is remarkably tough. A roll can sit in the back of a work trailer for months with no degradation. The only precaution is to avoid leaving the material exposed to direct sunlight for extended periods, as the rubber furring strips can become gummy when heated. Otherwise, the material is essentially indestructible on site. For projects where energy saving insulation techniques are being applied to the exterior foundation or walls, fiberglass lath integrates seamlessly over foam board without the corrosion concerns that metal lath introduces.
Some manufacturers offer non-metallic lath systems that are embedded directly into thinset over foam board rather than mechanically fastened. These systems, while effective, are significantly more expensive. For one recent project, the thinset-embedded system came out to about 30 percent more than the mechanically fastened fiberglass lath with a two-coat type-S stucco system. For most builders, the mechanical fastening approach offers the best balance of cost, reliability, and ease of installation.
Another advantage of fiberglass lath is that the same carpenters responsible for the weather-resistant barrier, flashings, and felt paper can also install the lath. This keeps the scope of work simple and allows the general contractor to maintain control over the water-tightness of the wall assembly. When the stucco crew arrives, they only need to focus on applying the stucco itself. Many contractors find they get better pricing from stucco subcontractors when the scope is clearly separated and the lath installation is handled by the framing crew.
Making the Switch to Fiberglass Lath
Fiberglass lath represents a genuine improvement in stucco and stone veneer installation. The material solves the rust problem that has plagued metal lath for generations while making installation faster, safer, and more reliable. The integrated foam-rubber furring strips eliminate the need for separate furring details and provide self-sealing fastener penetrations that preserve the integrity of the weather-resistant barrier. The weight reduction and elimination of sharp edges make the work less physically demanding and reduce the risk of job site injuries.
For builders who have been using metal lath out of habit rather than preference, switching to fiberglass opens up new possibilities. Decorative interior stucco features like range hoods and fireplace surrounds become more practical when the lath can be cut with scissors and folded by hand. Exterior foam insulation installations gain durability because there is no metal to corrode behind the stucco finish. The material performs equally well on foundation walls, above-grade exterior walls, and interior applications, making it a versatile addition to any contractor’s material lineup. Learning about blown in insulation options for attics and wall cavities follows the same principle: understanding the full range of available materials helps builders choose the right solution for each specific application.
The upfront cost is comparable to metal, the on-site durability is superior, and the long-term performance eliminates the rust and corrosion failures that shorten the service life of metal lath installations. For any project involving stucco or manufactured-stone veneer, fiberglass lath deserves serious consideration as the primary lath material.