How to Apply Sealant Into an Expansion & Control Joint on a Restoration Project


Back in January, we provided a few recommendations and procedures when working with expansion and control joints on a restoration project. We highlighted four steps: assess the condition of the existing sealant, select the correct restoration sealant replacement, remove the existing sealant and proceed with the necessary substrate preparation, and finally install the recommended backer rod and/or bond breaker, primer (if specific or required), and sealant. For this week’s blog post, we want to take these guidelines a step further and dive deeper into the installation process of a sealant on a restoration project. For a more detailed explanation of the steps recognized above, please visit the Technical Bulletins and Application Guides page on our website https://www.pecora.com/pecora-technical-bulletins/.

After you have assessed the joint, chosen the correct sealant, and prepared the joint, it is time for sealant application. For this section we will discuss five categories in the application process: sealant backing, mixing, dimensions, installation, and tooling of the sealant.  

Sealant Backing

You should always choose the appropriate sealant backing based on the available joint depth. Sealant backing will prevent three-sided adhesion, control sealant depth, and allow for tooling to ensure proper sealant/substrate contact. Foam cylindrical is the typical material backer rod installed and should be approximately 25% larger than the width of the joint. This is to ensure a tight compressed fit. Consult the sealant manufacturer for the recommended backer rod type. In joints where depth is not adequate to accept a backer rod, a polyethylene bond breaker rape should be installed.

Sealant Mixing (multi-component sealant only)

If a sealant requires mixing in the field, ensure that the manufacturer’s published mixing procedures are strictly followed. Thorough and uniform mixing is vital when installing multi-component sealants. Be sure to utilize the correct mixing equipment as recommended by the sealant manufacturer.

Sealant Dimensions

The correct sealant dimensions are critical when installing joint sealants and will ensure the sealant maintains it designed performance characteristics. Width of joint to depth of sealant should be two to one (2:1) with no joint depth being less than ¼”. Please see the image below which depicts the width to depth ratio guidelines of vertical and horizontal joints.

Sealant Installation

All sealing should be done when temperatures are above 40°F. Preferably, sealants should be installed at a median temperature and not as temperature extremes (low and high). All surfaces receiving sealant should be dry and clean. The sealant should be applied in a continuous operation using a professional grade cartridge-type caulking gun or bulk loading gun. Joints should be filled uniformly to the required sealant depth. Sealants may be recessed if required by manufacturer.

Tooling of Sealant

Tool the sealant with light pressure to spread the material against the sealant backing and joint surfaces. Use a tool with a rounded tip to keep a concave sealant profile in the joint and maintain the industry standard “hourglass” configuration. The sealant should be dry tooled unless the sealant manufacturer specifically approves otherwise. If approved, the tool may be dampened with a sealant manufacturer approved tooling agent (typically mineral spirits). Do not use water or soapy water as a tooling agent. Also, remember to avoid over tooling. Tool the sealant at windowsills and similar places so that precipitation, cleaning solutions, etc. will not pond. Any masking materials used are to be removed immediately after tooling while the sealant is still in its uncured state (wet).

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 techservices@pecora.com or by phone (800)-523-6688.

2 responses to “How to Apply Sealant Into an Expansion & Control Joint on a Restoration Project”

  1. Breck Juneau says:

    On horizontal joints if joints up to 1/2″ wide are 1:1 (1/2″:1/2″)and joints up to 1″ wide are 2:1 (1″:1/2″) would everything between 1/2″ to 1″ wide be 1/2″ depth? Otherwise a joint greater than 1/2″ wide would have less than 1/2″ depth if you go with 2:1,for instance 3/4″:3/8″. I’m just trying to understand so I do this right.

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