Using cast stone with EIFS   (12.06.2010)

The impact resistance of Exterior Insulating Finishing Systems is something that has evolved to significant improvement since it first became widely used in Ontario. There are several ways to increase the impact resistance of EIFS easily, but not all are plausible for every given project. Using a heavier weight of reinforcing fiberglass mesh is one option, as is using a thicker base coat to strengthen the EIFS wall from the inside out. However, there are always some situations that will arise where certain more vulnerable areas of the EIFS need to be protected only, and using heavier materials all over the entire wall isn't warranted or necessary. On occasions like this, adding cast stone to the design can provide added impact resistance as well as an aesthetic element that really stands out. Some areas that might need extra increased impact resistance measures in place are:

  • Near-grade EIFS: EIFS installed near the ground or even on the first storey of a home may have the odd bicycle thrown against it, might be used for storage in the winter or could be subjected to an accidental whipper-snapping when trimming grass near the wall.
  • At windows and doors: windows and doors often need to be washed, and more often than not they're near a light fixture that need a bulb or two changed every so often. Ladders will frequently be leaned up against this EIFS, and this could leave a dent.
  • EIFS next to heavily trafficked areas: If the EIFS is near a back patio, a walkway or a driveway, it runs the risk of being bashed in now and then, either due to carelessness or a runaway snowplow.

Small dents or bashes in EIFS are relatively simple to repair, but prevention is key. Cast stone offers another way to improve impact resistance in EIFS without too much added cost.

Cast stone is form of man-made stone. Minerals, cement, resin, colours as well as other ingredients are added to a mold, which creates realistic looking stone pieces that can be made to any specifications required. Cast stone can be hollow or solid, and it is usually sealed with a clear coating. Cast stone looks, acts and feels just like real stone, because it is real stone - it just hasn't been cut from real stone, so it's far cheaper.

Cast stone can be used to accent EIFS in many ways, and it can be used as an accent in and around window sills to protect the vulnerable EIFS from ladders or other activity near the windows. Cast stone also allows for nice, shallow slopes and further design possibilities that are not available for some EIFS applications because of fears of water intrusion. Cast stone does have a design drawback when compared to EIFS though like any stone or brick wall, it still requires mortar joints and cannot be installed seamlessly.

Sizes available

Some cast stone comes in predetermined sizes and shapes, other times it will have to be trimmed to fit specifications at the job site. The stone can also be made to be curved or arched for design purposes.

Installation

Cast stone is actually cast in expanded polystyrene foam molds, the same kind used in the insulation board of EIFS. Because the stone is sometimes hollow, it can also come with the expanded polystyrene foam still inside of the stone,making it easy to attach to a substrate using adhesive. Depending on the weight of the stone, different substrates can be used, all of which should provide some water resistance. Lath and stucco placed over wood-based sheathing or even EIFS base coats work, unless the stone is heavy, then it needs to be supported by a cleat.

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