Remedying EIFS Sealant Joints
Problems associated with EIFS can be complex and may not be repaired through improved waterproofing of the facade alone. Water penetration through faulty joints or at terminations of the EIFS may cause substantial damage in the EIFS or the underlying structure that must be addressed separately from the waterproofing.
Since no single method is best for all situations, each restoration method should be considered. To assist in determining which restoration method is best, a mock-up of the restoration method or methods should be installed on the building.
Because EIFS joints may become degraded for several reasons, the cause of the sealant joint problem should be examined to determine which restoration method is feasible or preferred. There are four basic types of sealant joint failures:
Adhesive Failure of Sealant - Adhesive failure is a loss of bond or adhesion of the sealant to a substrate. This failure may occur for three primary reasons: improper use of primer, failure to use a primer or improper surface preparation.
Sealant Deterioration - Up until the past several years, multicomponent polyurethane sealants were used on EIFS buildings. Such sealants are organic materials that deteriorate in the presence of ultraviolet light. This deterioration manifests itself in a loss of sealant flexibility and movement capability, or in some instances, reversion of the sealant from a cured to an uncured state.
Cohesive Failure of Sealant - Cohesive failure occurs when a sealant tears or splits within itself as the result of joint movement. Cohesive failure is usually the result of the sealant no longer being able to accommodate the expansion and contraction of the joint.
Delamination of EIFS Coating - Excessive sealant depth will reduce movement capability of the sealant, increasing the potential for substrate failure. Delamination occurs when the sealant overstresses the coating. This can happen at any time, but is particularly prone to occur when the EIFS coating is softened by prolonged exposure to moisture or water.
Four restoration methods are offered for the repair and restoration of EIFS and sealant joints. Any of the four methods may be appropriate for a specific building, however, the type of failure of the existing sealant joint will help to dictate which is the most cost-effective and practical restoration method.
Recessed Joint
In situations where the deteriorated existing joint has been recessed into the joint, it is possible to install a new sealant joint over the old sealant joint without removing the failed sealant. The existing sealant must be recessed at least «" from the face of the joint to allow a new sealant joint to be installed. Recess of greater than «" may allow a closed-cell backer rod or foam tape to be installed. Slit the existing sealant before applying a bond breaker tape over it in the joint.
The advantage of this method is that the joint can be made watertight without changing the appearance of the joint. Also, this method is fairly cost-effective, since the removal of the old sealant is not required.
A potential disadvantage of this procedure results from the finish coat having likely been installed into the joint. Any new sealant will probably be installed to the finish coat unless the additional step of removing the finish coat of the EIFS is performed.
Joint Removal
The joint removal restoration method includes a complete removal of all existing sealant and installation of new sealant. The challenging aspect of this procedure is the removal of the old sealant.
Removal of a reverted polyurethane sealant becomes very costly and time consuming due to the gummy nature of the deteriorated organic sealant. The gummy sealant is extremely difficult to remove from EIFS substrates without the use of solvents, which can damage the underlying foam insulation board. The EIFS cannot be easily abraded without causing damage to the coating and mesh. If the mesh is damaged, reconstruction of the joint will be required.
If joint failure is due to finish coat delamination and the sealant is not reverted or gummy, joint removal may be more cost-effective than other methods.
Removal of a cured failed silicone sealant is much easier than the removal of a failed organic sealant. A silicone that is cured and has failed in adhesion on one side of the joint can be cleanly cut away from the other side of the joint with a knife, and the remainder abraded away.
It may be possible to remove the old sealant and finish coat without damaging the EIFS base coat and mesh. The use of knives, wire wheel abrasion and grinders may effectively remove the old sealant and finish coat. Job site mock-up testing must be performed to evaluate the viability of this procedure.
Joint Reconstruction
Reconstruction of an EIFS joint is the most costly and labor-intensive method of joint restoration. This method involves cutting into the EIFS and reinstalling EIFS base coat, mesh, color primer and/or finish coat to match the original joint condition. The EIFS manufacturer would be involved in supplying the procedures and appropriate EIFS coatings to match the existing coating. In lieu of the application of a new EIFS finish coating, an elastomeric waterproof coating can be used to waterproof and coat the entire EIFS wall.
The reconstruction method would be appropriate if joints are sized too small to accommodate joint movement. The use of joint movement indicators can help assess whether joints are of sufficient width for a sealant to perform properly. Joint reconstruction also would be appropriate if a new penetration, such as a window, air conditioner, lighting fixture or other attachment, is being installed.
Joint reconstruction may also be necessary if the original EIFS design did not allow for the proper positioning of an expansion joint. It may be necessary for an EIFS manufacturer or industry consultant to evaluate this condition. In the reconstruction method, the sealant installation is as it would be with a new EIFS installation.
Joint Overlay
The joint overlay restoration method allows for waterproofing of joints in a cost-effective means that does not require reconstruction of the joint or removal of failed sealant. An overlay joint, commonly referred to as a bridge joint or band-aid joint, spans the existing sealant joint from the face of one side of the joint to the other. Traditionally, these joints have been applied in the field with a wet sealant. Field-applied silicone overlay joints have a proven track record of performance on EIFS and other construction materials.
With the introduction of pre-formed silicone seals such as Dow Corning's 123 silicone seal, the variability of field-applied overlay joints has been eliminated. The pre-formed seal can provide a very cost-effective watertight joint due to the labor savings associated with not having to remove the failed organic sealant. The seal is applied directly over the existing joint using a silicone building sealant as the adhesive.
Restoration of the EIFS wall beyond the existing joints can be complex, requiring the need for a qualified industry consultant who is experienced in EIFS restoration. Provided that the wall is essentially sound, waterproofing and restoring the wall can be accomplished with the use of sealants and compatible elastomeric waterproof coatings.
When an EIFS wall is showing hairline cracks of 1/16" or less, an elastomeric waterproof coating can effectively bridge the hairline cracks and waterproof the wall.
In areas where hairline cracks are in excess of 1/16" width, there may be need for a control or expansion joint at this location. An EIFS expert should be consulted in these cases. If a new joint cannot be installed by the joint reconstruction method, the use of an overlay joint is effective. For an irregular hairline crack, a field-applied wet sealant application is recommended. A compatible elastomeric waterproof coating then can be applied over the entire wall to ensure a watertight wall should further hairline cracks develop.
User Comments:
No comments added
Add your comment
Fill out the fields below:
|
