FAQ: What are the Substrate Surface Preparation Requirements Before Sealant Installation?
Substrate surface preparation requirements are determined by two factors: the type of substrate and whether the project is new construction or restoration. Substrates are classified into two categories: non-porous and porous. Non-porous substrates such as metal, plastic and glass are prepared utilizing the solvent wipe, two cloth method. This surface preparation method includes a wipe with solvent (typically 100% isopropyl or denatured alcohol) using a clean, lint free cloth followed by a dry wipe with a second clean, lint free cloth. Porous substrates such as masonry and precast concrete are prepared via one or a combination of following: abrasive blasting, pressure washing, grinding and/or wire brushing. The condition of the porous substrate will determine the surface preparation technique required. The ultimate goal is to achieve a clean, dry and contaminant free substrate surface.
For this week’s blog post, we focus on a frequently asked question regarding our sealants: what are the substrate surface preparation requirements before sealant installation? In previous posts we have touched on surface preparation when discussing restoration recommendations and procedures. Today, we dig a little deeper and focus the difference between new construction and restoration surface preparations, the type of substrate as a factor, and the importance of ensuring the joint is properly cleaned and ready for installation.
In new construction projects, the substrate is green or new and does not require too much preparation. We recommend following these three steps in order to prepare a surface for application.
Clean out joints immediately before installing joint sealants.
Non-porous surfaces must be cleaned with a solvent compatible with the substrate before the sealant is applied. Use the two-cloth method—wipe with solvent on the first cloth immediately followed by a dry rag wipe.
In the event of exposed aggregates in precast concrete, diamond grinding is recommended to provide a clean and uniform concrete surface allowing for proper sealant adhesion and performance. Diamond grinding is a technique used to correct irregularities, including minor pits and roughness on concrete surfaces. After initial surface preparation and cleaning is completed, the application of a primer, if recommended, should occur followed by sealant application.
Adhesion surfaces must be clean, dry, and free of dew or frost.
For porous substrates: oil-free compressed air, abrasive blasting, high pressure water (allow to dry), grinding, or wire brushing. For more information, please contact our Technical Service Department at (800) 523-6688.
For non-porous substrates: use the two-cloth method—wipe with solvent on the first cloth immediately followed by a dry rag wipe. See → Pecora Technical Bulletin # 74- Two Cloth Cleaning Method.
When working on restoration projects, the substrate preparation is a little bit more involved. We recommend following these three steps in order to prepare a surface for application.
Sealant and Residue Removal
Cut away failed sealant as close as possible to the joint edge and remove all existing sealant and backing materials.
Clean all joints of contaminants and impurities to the depth at which the new sealant and sealant backing are to be installed. This may be accomplished by the following methods:
Porous Substrates: Diamond grinding for concrete, masonry, brick, and similar porous substrates to expose virgin substrate.
Non-Porous Substrates: To remove most if not all residual sealant, use a razor knife to cut out non-porous substrates such as metal and glass followed by a solvent wipe.
EIFS Substrates: Extreme caution must be taken when restoring EIFS joints. Sealant must be removed by razor knife only in order to maintain an undamaged EIFS substrate surface. Grinding is prohibited. For more information, please contact our Technical Service Department at (800) 523-6688.
The Pecora Silspan EIFS restoration system may be utilized in order to prevent any substrate damage possibly caused by attempting to remove existing failed sealant.
Blow dust, loose particles and other debris with oil-free compressed air. Make as many passes with cleaning tools and compressed air as required to ensure that joints are clean and free of existing sealing materials and/or other dirt and debris.
Sealant primer may be required and should be determined by the manufacturer or applicator through field and/or laboratory adhesion testing.
If primer is required, primer must be installed per the manufacturer’s application procedures in regard to appropriate primer selection, coverage rate, and dry time.
For more information, sealant application recommendations, or information on the installation procedures, we urge you to contact our Pecora Corporation Technical Services Group. Our expert team is highly qualified to recommend the proper solution for your project. Our Technical Services staff offers training in product technology and use, provides the technical assistance you require in the planning and implementation of your project. They can be reached by email firstname.lastname@example.org or by phone (800)-523-6688.
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