Process

At Cornerstone Exteriors we recognize that the decision to renovate your house can be a big and potentially stressful one.  In this section we hope to provide some insight and tips for prospective homeowners and businesses who are considering investing in the exterior of their home and business.

First, EIFS (Exterior Insulation Finishing System) is not the old rock-dash/lathe and plaster tri-coat stucco found on many older homes.  EIFS is the most researched exterior cladding system on the market and has significant benefits over traditional exterior cladding system.  With that said, a complete EIFS system is complex and requires training to install it properly.  When choosing to invest in stucco it is important to insure that any contractor that claims to be certified to install the system follows the strict guidelines outlined by the industry in order to guarantee the quality and provide the maximum life cycle of the product.  Below is the comprehensive breakdown of what an EIFS system entails.  Each step must be followed to industry specs in order to maintain the integrity of the product over the course of its life.  

1.  Sheathing/Substrate

With EIFS (and most things in life) the key to a lasting investment in EIFS stucco starts at the foundation.  EIFS stucco can be installed over multiple substrates (base layer) such as masonry, plywood, Densglas Exterior Sheathing and others as long as they are prepared properly with the proper product to insure optimal adhesion and moisture and air barrier.  This leads to step number two.

*TIP - When your contractor installs EIFS, make sure they are installing over approved substrates at all times.  This means that there is no lose or spalling brick that has not been sealed, flimsy (foam nailed to studs only or 1/4" sheathing) or other loose and dusty areas.  

Here is a good source for exterior sheathing options: https://continuingeducation.bnpmedia.com/course.php?L=233&C=732&P=2

2.  Waterproof Air Barrier

 In most cases, using a polymer modified cement specified by the supplier or rubberized membrane to completely seal the substrate allows the foam being applied to adhere properly.  Due to the cost, many contractors will opt for lower cost solutions that will most certainly impact the life cycle of your system.  It is important to make sure that your contractor follows the industry specifications for the system being installed on your home or building.

*TIP - Each substrate has its own specifications and requires its own unique moisture barrier application.  While masonry is capable of being sealed by both polymer cement and a rubberized membrane, plywood and other wood substrates can only be sealed using the rubberized membrane.  If your contractor is using Typar as a base layer over your home he or she is most likely installing the system incorrectly and should be stopped immediately.

3.  Adhesive Primer

This is an area that, in concert with the first two, comprise much of the failure points for EIFS installations.  In fact, many contractors will forgo the primer altogether and opt to screw on the foam sheets over fabric (Typar) vapor barrier using plastic washers because it requires less time, material and therefore money.  This method is NOT recommended by any EIFS manufacturer/supplier and this will void any inherent warranty implied by the supplier.  For a system to be installed correctly, each sheet, moulding and detail must be adhered using a notch trowel of no less than 1/2" in order to allow for any moisture to evacuate from behind the sheets while insuring proper material to maximize adherence.  Failing any of these recommendations greatly reduce the resilience and strength of the adherence and the system itself.

*TIP - This step is vital for the life cycle of your investment.  Material can be watered down beyond specifications, cured prematurely by excessive heat and wind or spread too thin which all lead to a compromised EIFS application.  

4.  Insulation/Foam Sheets

This is where an EIFS stucco application pays for itself in the long run.  While the minimum industry recommended size is 1.5" expanded polystyrene sheets (EPS) here at Cornerstone Exteriors we recommend the use of 2" EPS in order to gain a continuous R-value of 8.8 over the whole area.  After the foam has been installed, it is then sanded down to even out surface imperfections and undulations as well as assist in the adherence of the base coat and mesh in the next step.

*TIP - Take care to make sure that your installer is installing the correct foam system.  While 1" EPS is available from all manufacturers, it is meant only as a supplementary addition in the form of aesthetic build-outs and other cosmetic applications and should never comprise the majority base of any EIFS system as it is less resilient, rigid and prone to cracking while providing significantly less insulation value.

5.  Reinforcing Mesh

The reinforcing mesh comprises the majority of the exterior resilience of an EIFS application.  Every manufacturer insists that every square inch of foam be covered with embedded fiberglass mesh that is overlapped to insure seamless coverage.  This extends to mouldings (both prefab and hand cut), control joints and any other area that foam is exposed to the elements.  Failure to do so will certainly result in cracks, peeling and foam degradation over time.  

*TIP - Anywhere where an EIFS system meets a different surface such as stone or flashing it must be back wrapped (mesh wrapped around behind the foam) with either a prefabricated coated band or field mesh off the roll.  Failure to do so will degrade the foam underneath.

6.  Base Coat

This step goes hand in hand with the reinforcing mesh.  This material is a polymer cement that is used to embed the mesh and adhere it to the EPS foam sheathing.  The base coat acts in tandem with the mesh to provide the resilience that will turn the foam in to a hardened surface, spanning the individual sheets and transforming the EPS insulation in to what is more recognizable as a finished product.  As with the mesh, the polymer modified basecoat must cover the entire exposed foam insulation otherwise it will degrade.  As with adhesive primer (which is often the same product), dilution, premature curing and improper mixing will jeopardize the resiliency of the coating and limit its ability to fulfill its role.  

*TIP - Keep an eye out for discolourations of the polymer cement usedas this may indicate freezing, improper mixing or premature curing.

7.  Adhesive Primer

This coat is often considered optional depending on the manufacturer or system being used.  It is often recommended by the manufacturer for higher end stucco systems but is usually not formally required to fulfill industry specs.  With that said, an additional coating of primer helps smooth out any imperfections and add an additional layer of resiliency to the product.  For most applications, Cornerstone Exteriors recommends and performs this stage, especially on higher detailed, highly variable applications.

8.  Finish Coat

At last, the final stage.  The finish coat is made from an acrylic base with either a crushed marble or quartz aggregate that brings out the textured look in the application.  Cornerstone Exteriors usually uses STO products unless otherwise specified on a project which opts for marble as it retains its cosmetic integrity as it does not change over time.  The finish coat is hand troweled on and "floated" over with a specialized plastic trowel made for the purpose of evening the coating and coaxing out the right textured finish.  This is subjective but most would agree after seeing the difference that a superior final coat has an even, smooth and consistent finish without any "burns" from inconsistent drying or "busy" spots where the floater had brought too much texture out in a certain spot.  

*TIP - Finish coats come in several looks ranging from a fine aggregate often used on details and mouldings, all the way to a swirl type finish that creates the look and illusion of textured rock. 

Additional Notes

A good stucco job can go a long way to improve the value, efficiency and cosmetic appeal of your home or building.  Keep an eye out for bare foam in hard to see places, foam pressed down on a roof line, showing mesh or discolourations of the polymer cement used.  This may indicate an improper installation and are key indicators that the system was not installed as advertised.  At Cornerstone Exteriors, it is our mission that our customers are as informed about the process as possible and that from the initial hand shake to the last they are content that their house is in good hands,