With all of the terminology surrounding stucco, it can be confusing trying to figure out what certain terms mean and can seem foreign to some people. Lath is one of those terms used in the stucco process that can be confusing to some people but it is pretty easy to understand, you'll see!
What Is Stucco Lath, Anyways?
Lath is simply the first step in the stucco process. It consists of water resistant paper, (sometimes eps foam) wire and other metal components that make up the essential “framework” for the cement to be adhered to. It attaches to the substrate and is the structure for the following coats.
Different Types Of Stucco Wire:
The wire comes in various types and styles to match specific commercial, residential and personal specifications that one may encounter. There are also different gauges of wire, meaning the thickness of the wire itself.
Stucco wire is thicker and stronger than say “chicken or poultry wire” and is furred, meaning it sticks out of the wall a little bit, to allow the cement to “key” in to the wire better, which is another way of stating that the wire is embedded (sits in the middle) into the base coat.
Three Coat And One Coat Stucco Systems:
Seventeen gauge wire is stronger than 20 gauge wire, the smaller the gauge “number” the stronger the wire, and is usually used in three coat stucco systems. The lighter-weight 20 gauge wire is used for a one coat (sometimes referred to as 2 coat) stucco system.
The three coat system uses a “scratch coat”, a “brown coat” and then a “finish coat” in the plastering process, hence the reason why it is called a “three coat system”.
A one coat (or two coat) system uses Styrofoam in place of the “scratch coat”, then a “brown coat”, then the “finishing coat”. There are more than one coats of cement, but this system is referred to as a “one coat system” or "two coat system". The brown coat and finish coat are the two plastering coats used in these systems and calling it a two coat system makes more sense, in my opinion.
Corner Aid, Weep Screed, Etc.
There are other pieces included within the lathing stages that are equally important as the paper and wire itself.
These are made out of similar materials and are essentially “stopping points” for the stucco to end on a wall. For example, corner aid is used on corners to help the cement mixture stick and it adds a lot of strength on an otherwise weak area of the house.
The Plaster (or J) Stop is actually a "J" shaped metal product, that can be found in Copper, Aluminum, Stainless Steel, and Galvanized Steel. It is a termination point for stucco which is available with or with out 3/16″ Weep Holes.
Weep screed is found at the bottom of walls and has many holes in it to allow for proper water drainage. It comes in two different styles: a 90 degree angle ("J" shaped too) and a 30 degree angle (referred to as number 7).
The two are used for both three and one coat stucco applications and come in different sizes. Here is a good link that describes it in more detail: weep screed article
An expansion joint is used to break up the stucco in order to lessen the chances of cracking. It can be very wide (3″ or more), but for most residential applications, it is somewhere around 5/16 of an inch wide.
It is usually painted to match the color of the stucco and is generally needed where there is an area of stucco greater that 120 square feet or more on walls and 100 sq. feet on soffits. Other conditions apply where expansion or control joints may also be needed but the square footage above is a good general rule.
Walls without natural breaks (such as windows and doors) will have a far greater chance of developing cracks without implementing an expansion joint.
Arch aid acts the same way corner aid does, it simply bends to conform to arches and curves. It can be a bit tricky to install and does take some skill to master, but will make all the difference in the world around archways.
Corner aid is used on corners and edges that need to be defined and strengthened. It comes in two different styles, bullnose and straight. The straight forms a 90 degree angle and the bullnose is designed for rounded corners. They come in 8' and 10‘ lengths and are usually installed with staples or nails.
Nails And Staples:
In order to fasten the metal lath to the substrate (plywood, masonry, etc.) you will need to either nail or staple the wire to the substrate itself. Typically, staples are used to do this, along with a staple gun and a compressor.
It is also possible to nail the wire off by hand for smaller areas, or to hang the wire, plaster stop, weep screed and/or corner aid. For larger areas, a stapler should be used as it will save a lot of time, but is not mandatory. All fasteners should be galvanized or at least rated for exterior use to prevent corrosion from taking place.
Nails are a great way to quickly hang wire and other lath components quickly and accurately. There are a few types used in stucco applications and becoming familiar with each type can be very helpful.
- Dog eared nails (or furred nails) are not really used anymore, because the wire itself is furred. These nails were used a few decades ago to help hold the wire off of the wall itself. They should only be used if you are doing a remodel that uses these types of nails, otherwise don’t bother with them.
- Roofing nails are used sometimes because they are usually galvanized and have a large head on them, which holds the wire in place very well.
- Galvanized 4 penny nails are also use in three coat stucco systems and are bent over after being driven in halfway or more and holds the wire in place.
- Staples are used more often than not and are a quick way to attach the wire to the substrate. There are specifics on the size of the staple, including the length of the staple and the size of the crown, check with your local building department. You will also need a small compressor and staple gun to shoot these in.
The paper is actually infused with an asphalt that is resistant to water and moisture. It is available in a couple of different thicknesses and can be found in a one or two ply roll. It is usually attached with a stapler that is made for roofing applications.