There are a wide range of different wires that are used in the lathing process of stucco these days, so I wanted to write this post to discuss some of the different kinds available and what they are used for.
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Certain types of wire are better suited for different things and knowing which type of lath to go with will make the job a whole lot easier to do.
This particular wire is commonly used in the three coat stucco system and is a fairly strong kind of wire.
It is furred, which means that it sticks off of the wall a little bit (about a quarter inch or so) so that the stucco mix can "key" in behind it. You really want the wire to be in the middle of your base coat, for the best possible installation.
The two different pictures show the same gauge wire being used but the top picture is using wire that uses a square pattern and the lower one uses the more common honeycomb pattern.
Both will work just fine and are acceptable for three coat stucco systems, just a personal preference type of thing.
In order to achieve a furred product, the wire is crimped by a machine, so when it is rolled out along the wall, it will stand off of it a bit, roughly a 1/4".
When installing the wire, you want to make sure these "crimps" are facing in so there is a gap between the wall and most of the wire.
The wire can come in a non-furred version but is hardly used because you would have to use furred nails instead and most codes require the use of furred wire anyways.
The wire is typically galvanized, in order to prevent corrosion of the wire over the years.
The holes in the wire are approximately 1 1/2 inches apart (depending on manufacturer), which doesn't really matter but is just another identifying factor for three coat stucco wire.
This wire is the same as the 17 gauge, but a little thinner and flimsier. It is used in 1 coat stucco applications and has smaller openings than a 17 gauge wire and it not nearly as strong either.
There is really only one style and it resembles the look and thickness of traditional chicken wire. This is really the only type of wire that is used for a one coat stucco installation and the wire is made specifically for it too, so keep that in mind.
The one coat wire also has smaller spacing between the holes, which is about 1", compared to 1 1/2" spacing that the three coat wire has.
This type of wire lath is intended for ceilings and soffits. The design is made to hold the plaster in place, while minimizing the amount of fallouts.
It resembles expanded metal lath, in a way but is much more rigid, due to the grooves that run down the length of the wire.
The picture on the right shows the ridges in detail and this is how it is installed on a ceiling, with the points facing up.
High rib lath is only used for ceilings and not for anything else. That is just from my experience, I am not saying it can't be used on a wall, it just isn't and I'm not even sure that building codes would allow it to be used on a wall.
It is pretty hard to cut with a pair of tin snips, I usually end up using a small 4" grinder with a metal cutting wheel to make it go a bit quicker.
This particular lath has a much smaller pattern in the wire itself. It allows the cement to bond to it very well and is usually used for patches, transitions and uneven surfaces.
You can use it for your entire project, if your building dept. will allow it but it is more expensive than traditional wire and most people won't use it because of that reason. It also works great for stone veneer projects!
Most of the sheets you will find will not be pre-furred, so they won't be up to code but you can get them furred (like the image to the right shows), which is usually a special order item.
They come in three different weights and these are measure by the weight (not sure of the metric) of the screen per square yard. These are: 1.75, 2.5 and 3.5, (2.5) being one of the most common weights used in the industry.
This type of wire has the paper attached to it already and is used for open stud applications mostly. A strand of wires runs the length of the paper and wire and is inter-weaved, connecting the two together.
It has a bottom and top edge that are designed to fit on top of one another and overlap the paper and wire simultaneously.
I typically will apply two layers of 60 minute building paper to the wall before I use this wire because these tend to have a tendency to leak a lot easier.
No shear on the wall means that there is hardly any backing for the paper and wire so installation is a bit harder and takes a little bit longer.
There is another alternative to metal and that is a fiberglass mesh (Spider Lath) that has furring strips along the back of it, that is code compliant and can be used instead. It is easier to cut and lightweight, making it a lot more user friendly.
It is hard to get though and much more expensive than traditional metal lath. I was only able to find it on Amazon and nowhere else, even my local stucco supplier can't get any of this stuff!
You can cut it with a regular pair of scissors or a utility knife and it is attached the same way as traditional metal lath is, either stapled or nailed (approved fasteners) on with galvanized or code specified materials.
Below is a quick video that shows how the whole process works and what you can expect if you choose to go this route.
The videos is all about the lath and scratch process for a stone veneer project but has valid info that applies to stucco as well.
Wooden "slats" that are run horizontally are also a pretty common lath used, well it used to be, anyway. We don't typically use wooden lath as much because it is more work to install and more expensive, compared to modern materials and techniques.
The picture shows the interior of a home that used wooden planks that the stucco "keys into" but wood lath can also be found on the outside of a home too. There is not really a whole lot more to say about the wooden lath, it is a pretty simple and self-explanatory process.
Nailing Patterns For Wire: Nailing off nearly all types of wire is the same, in essence, depending on your local building codes and engineering specs. Most wire requires you to nail it off at a "6 and 12" interval.
* Check your local building code to see what is required in your area, though!
This means that nails and/or staples around the edges of windows, corners of walls, bottom & top of walls will require a fastener every 6 inches and nailing every 12" on the studs themselves (vertically).
What Is Furred Wire: Furring is basically a simple dimple that is made to hold off the wire off of the wall (evenly) about a quarter of an inch. These dimples are strategically placed on the wire to evenly hold the wire off of the wall.
The picture on the right shows the wire (three coat stucco) furring in great detail. Notice the staple holding the wire in place, touching the wall and the rest of the wire has a gap.
What Is K Lath: K lath is really a brand of wire made by the company Tree Island but has become a more "generic term" used for wire, particularly the square shaped wire found on most commercial stucco jobs (as shown in the first picture of three coat stucco wire).
They make wire for nearly every type of stucco application though.
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What's The Best Way To Cut Metal Lath: Typically a good pair of tin snips will do the job, either smaller ones or the larger types available nearly everywhere. I use a small grinder with a metal cutting blade to cut high rib lath because it is cleaner and way quicker than using any type of metal cutting shears, due to the "ribs" in the wire.
How Much Should I Overlap Wire: This depends on the wire type, more specifically how large the holes in the wire are. The larger the holes, the more overlap you will want to have. The wire that uses smaller, tighter holes requires less of an overlap.
The "industry standard" is a 6" overlap for standard wire (three coat and one coat stucco wire) and the other wires will be somewhere around a 3" overlap but check with the manufacturer and local building codes first.
These are MINIMUM requirements, so more is okay but don't try to save on wire by using less overlap, wire is cheap compared to problems that could arise later due to a less than recommended wire overlap distance.
Did I forget anything? If so let me know in the comments below, any questions or comments you may have. Thanks!
Stucco, plaster and veneer would easily crack under types of stress and deflation in the process of building construction and residential living. Metal lath is used to prevent or decrease wall crackings in either pumped or troweled application. Sheet metal lath is slit and expanded into small diamond openings (approximately 11,000 per square yard).
We supply sheet metal lath in two types: diamond metal lath and rib meta lath. Flat diamond metal lath is nor used over solid surface like gypsum, concrete and wood sheathing. Because flat sheet will only cause the stucco to bond only to the sheathing and not complete the embedding process. Therefore expanded metal mesh is usually self-furred: dimpled and V-grooved. Diamond metal lath, for its unravel feature, is especially suitable for high strength needed architectures. Rib metal lath is expanded metal made sheet with ribs to increase the strength of it overall structure. Strip lath and corner lath are also available for installation convenience.
Diamond Metal Lath:
Flat diamond metal lath could only bond to the sheathing but not complete the embedding process for covering a solid surface like gypsum, concrete and wood sheathing. Therefore self-furring metal lath came into being. Self-furred diamond metal lath is generally used as reinforcement of plaster for solid surface. And it is divided into two types: dimpled and V-grooved. The two kinds of diamond metal lath is showed below in DML-01 and DML-02.
SML-01: Diamond metal lath with dimples shapes.
SML-02: Diamond metal lath with V grooves.
SML-03: Plan and section of diamond metal lath with dimples shapes.
SML-04: Plan and section of diamond metal lath with V-grooves.
Specification
Material (Conforming to ASTM A653/A653M):
Weights (per Sq. Yd.):
Mesh Size:
Thickness:
Sheet Size: 27" × 96".
Number of Grooves per Sheet: 5.
Weights per Bundle:
Packaging:
SML-05: diamond metal lath
LWD: 17.7 mm, SWD: 8.3 mm.
Application:
Rib Metal Lath
Rib lath is the most rigid for all sheet metal laths for its ribs running the whole length of the sheet added additional strength. Rib metal lath is commonly used for soffits and ceilings. Two types of rib metal lath are supplied: Hi-rib lath and flat rib lath, among which the most popular type is 3/8" high rib and 3.4 lbs./sq. yd.
Flat-Rib: 1/8" for all ribs on the lath, spaced at 3" on-center. The 3" wider space is provided for wooden or metal supports. This lath is ideal for machine applied plaster, backed with 2 strips of backing papers.
Hi-Rib Lath: 1/8" rib between two 3/8" ribs, spaced 4" every pairs of 3/8" ribs. Hi-Rib lath is used primarily in horizontal applications or for framing spaced no more than 24" on center. Strips of 3" backing paper should be attached to the spaces between the 3/8" ribs in order to minimize blow through of plaster when machine applied as showed below in picture SML-09. This lath should be installed horizontally on vertical walls or ceilings.
SML-06: Hi-Rib Lath with 3/8" ribs and 1/8" ribs in the middle of 3/8" ribs.
SML-07: Flat rib lath with widths of two opening holes being 1'.
SML-08: Hi-Rib Lath with widths of two opening holes being 1'.
Specification
Material (Conforming to ASTM A653/A653M):
Weights (per Sq. Yd.):
Mesh Size: 12.7 mm × 7.1 mm.
Sheet size:
Weights per Bundle:
Packaging:
SML-09: Strips of 3" backing paper should be attached to the spaces of 3/8" ribs with margin.
SML-10: Rib metal lath would be bound together tightly for the transport security.
Application
Made of expanded metal, rib lath is the ideal material as a background for plaster, render, stucco application in construction of suspended ceilings partition.
Strip Lath and Corner Lath
Strip lath is expanded diamond metal lath formed into strips with smooth edge and used for reinforcing joints of solid based. It is normally attached diagonally at the corner of all openings as doors, windows or areas prone to crack for reinforcement. It may also be used to span pipe chases or reinforce other stress points such as the corners of openings in the stucco membrane within the lath system.
Specification:
Roll Size:
Short Rolls: 4" × 8', 6" × 8';
Long Rolls:
Packaging:
SML-11: A roll of strip lath used for areas prone to crack.
Corner lath came into being by strip lath bent into obtuse angle with smooth edges. It is used in where intersections happens&#;wall meet walls or ceilings and ground.
Table 1: Specification of corner lath Design Flange width Length Pieces per carton Feet per carton Galvanized weight per lineal. feet CL-01 2" 96" 75 600 84 lbs. CL-02 3" 96" 75 600 118 lbs. CL-03 2" 48" 125 500 84 lbs.Feature
Application
Accessories
Installation
Where paper-backed metal lath is applied over wood based sheathing for cement plaster (stucco) reinforcement, an additional layer of Grade D paper shall be installed on the sheathing.
Codes and Standards
SML-12: Galvanized carbon metal made corner lath.
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