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Sealant Top Tips for Siding Installation

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Sealant Top Tips for Siding Installation

EW: Why are the quality and proper use of sealants important?

LO: You want to protect your brand equity and reputation with those who hire you. By selecting the right exterior sealant and installing it  properly, you help eliminate callbacks and ensure greater longevity of your craftsmanship.

It is important to select a sealant that expands and contracts and offers good adhesion properties so it bonds with the substrate, and does not break with substrate movement.

A sealant helps protect the integrity of the wall assembly against wind and drafts, as well as water and noise penetration. It also helps compensate for movement between construction elements. When applied properly, it provides a nice visual appearance.

There are five main types of sealants: water-based latex/polymer, polyurethane, solvent-based, silicones and hybrids.

EW: What are top tips for proper sealant selection?

LO: Consider the sealant’s elasticity, adhesion strength, durability over time, color offering and application characteristics. The sealant should be compatible with the building materials being used and appropriate for use in applicable weather conditions.

Some sealants are not recommended for use in certain weather conditions. For example, latex sealants may be difficult to apply in cold weather as they begin to harden at colder temperatures. Applying latex sealants to wet or frozen surfaces is not wise, nor is exposing them to water (e.g., rain) too soon after application­-the water-based sealant may be more likely to wash away. Sealants such as polyurethanes and silicones require atmospheric moisture to cure. Environments with low atmospheric moisture (e.g., Arizona) or cold dry weather may slow the cure of these sealants.

It is important to use a sealant that has strong adhesion to the substrates being used, which can be measured by peel strength.

Also, consider the ease of extrusion at various temperatures. As the product temperature drops, extrusion can become very difficult. This may require heating of the product. At higher temperatures sealant consistency may become too sloppy, resulting in poor control by the applicator.

EW: What are top tips for proper installation?

LO: Once the proper sealant has been selected, it is important to understand the correct techniques for application on your job.

For surface preparation, the application area for the sealant must be clean and free of foreign materials such as sand, dust and oils.

If you're installing windows into a siding remodel, assess the existing assembly for any hidden challenges. Apply a uniform 3/8" bead to the window flange for a proper gasket between the window and wall. With fillet and butt joints, it is necessary to avoid adhesion to three different surfaces. Not all sealants need to be tooled to achieve a finished look-always refer to the manufacturer's application instructions for specific recommendations.

Skinning and skin formation occurs as a sealant dries or cures. It develops a dried film on the outside before the inside material dries out or cures. Skinning minimizes dirt pickup. The time to achieve this property is the skin formation time. A skinned sealant should not be tooled. A typical skin formation time is 10-20 minutes.

Curing time is the amount of time that a sealant layer requires to reach its full intended performance characteristics. The speed at which a sealant cures depends on sealant ingredients, cure temperature and relative air humidity.

Most sealants specify application temperatures between 41° F (5° C) and 86° F (30° C), but there are sealant solutions that can be used in extreme temperatures from as low as 0° F (-18° C) up to 140° F (60° C). Note that lower temperatures may prevent proper curing of water-based sealants. Excessively hot weather may accelerate the sealant cure time, resulting in bubbling and shortened working life and tooling time. It may also cause sagging.

EW: What are some sealant failure factors?

LO: The biggest factors that affect the performance of the joint are proper sealant selection and bead size. This is important for siding types with linear expansion and contraction. Some sidings may shrink with reduced moisture or temperature causing the joints to open up. This stretches the sealant, so it’s important that there is sufficient sealant to span butt joints and termination joints.

It also emphasizes the need for two-sided attachment rather than three-sided attachment so the elongation of the sealant isn’t compromised.

The intent is to allow the sealant to expand and contract as it bridges between two surfaces.

Exterior cladding like LP® SmartSide® siding, trim and soffit are relatively dry at installation and will expand slightly rather than contract. This mode of equilibration will compress rather than stretch the sealant. While some sealant manufacturers recommend a 3/8” bead, it isn’t necessary or feasible with LP SmartSide products. LP SmartSide lap and trim require a 3/16” space at each joint to accommodate expansion after installation.

Once the initial expansion occurs, there is relatively little movement in the material so there is minimal stress applied to the sealant.

From a homeowner standpoint, the aesthetic look of the finish is noticed, so choosing a sealant with color-match capabilities is also important.

For more information about LP SmartSide Trim & Siding, please visit or call toll-free 888.820.0325.

A sealant that touts strong competitive attributes is OSI® QUAD®, which is specified for siding, windows and doors. OSI cites its QUAD product as an advanced-formula sealant that is a solvent-based thermoplastic sealant. It offers premium adhesion and elasticity characteristics and can be used in most extreme weather conditions. The formula skins over in a short time to resist dirt and dust pickup and offers long-term durability. QUAD is available in 350+ colors and is also paintable with either latex or oil-based paints. For more information, please visit

For reference for sealant use on exterior applications, OSI recommends reviewing the following document from the American Society for Testing and Materials (ASTM): ASTM C920: Standard Specification for Elastomer ic Joint Sealants

This information and the websites identified above are provided solely as a convenience to the reader. They are not intended to state or imply that the editors of Engineered Wood or LP Building Products sponsor, recommend, endorse or are affiliated or associated with the companies or products listed.