EIFS – Flashing versus embedded trim

With regards to Exterior Insulation Finishing Systems, embedded trim is “embedded” or bonded into the coatings of EIFS, whereas flashing is a loose material that is placed against EIFS coatings.

In Europe, there are many manufacturers who produce numerous styles of embedded trim suited specifically for and that are compatible with their EIFS. In North America, embedded trim is just another supply that is purchased separate from the EIFS and rarely comes from the manufacturer themselves, although some do produce it and include it in their package of EIFS components. Other manufacturers will provide specifications for the embedded trim that should be used with their EIFS, and others don’t seem to care one way or another what type of embedded trim is used. This article provides details and guidelines on choosing embedded trim.

Does the job require embedded trim?

Embedded trim is used to finish off edges of EIFS walls. It can be used on EIFS with or without drainage and if done properly can help the system eliminate water intrusion issues without the need for back wrapping. Trim can provide colour, aesthetics, as well as design components, and whether trim is optimal for a particular job depends on many factors such as climate and preexisting building design.

Does the manufacturer allow for the use of embedded trim?

Altering the design or going against specifications that come with EIFS and that are set forth by the manufacturer can void warranties and remove accountability should the system ever fail or result in issues later on down the road. As stated above, each manufacturer is different with regards to how they would prefer embedded trim to be used with their EIFS, and it’s important to consult the manufacturer before deciding on whether or not to use embedded trim. They may even be able to suggest types, materials or styles of trim that work best with their system.

Material choices

Like flashing, embedded trim can be used with EIFS with drainage to reroute water away from vulnerable areas and prevent it from entering the EIFS wall. The only difference is that small cavities will have to be perforated into the trim to allow for water to escape from the drainage cavity.

Different types of buildings require certain materials to be used depending on their fire code regulations. For example, heat rises and flames plume upwards. This fact is especially important if EIFS is being used on non-combustible walls, like on commercial buildings. Above a window, where flames will exit and heat upward first, fire-resistant or nonflammable materials should be used for embedded trim, whereas embedded trims made of plastic, which melts, can be used on combustible walls.

Not all sealant is created equal

Many times, sealant used with EIFS is made specifically for and is perfect when bonding things to EIFS. However, when it comes time to bond EIFS to embedded trim, the sealant might not be optimal for adhering to whatever material the embedded trim is made of. Check your sealant before using it to make sure it’s compatible.

Temperature, humidity and climate

Atmospherical and meteorological conditions can affect the use of embedded trim. The Ontario climate is pretty safe for most embedded trim, although the temperature variations between winter and summer, the rapid freezing and thawing and bright sun can all work towards deteriorating embedded trim. The material you choose for your embedded trim is important in this regard depending on the project at hand.

Base coats

The thickness of the base coat when adhering embedded trim to the EIFS is important. The thicker the base coat, the better the embedded trim will be adhered to the EIFS, and as a rule it should be as thick as possible – thicker than the whole of the base coat including the reinforcing fiberglass mesh that is on the rest of the wall.

A higher resin content and lower cement content in the base coat will also allow the embedded trim to adhere better to the EIFS.

Shifting and stretching

Many materials shift, expand or contract due to fluctuations in temperature. Because all materials, including EIFS materials, shift at different rates, adjacent components like embedded trim should be made of materials with similar thermal expansion values, information on which, are usually available directly from the manufacturer about their EIFS components.

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