The rim joist area is notorious for air leaks. Sealing the gaps and cracks around this part of a house can lead to significant energy savings. Our detailed guide walks you through the main steps of sealing rim joists using insulating foam sealant.
Rim joists are lateral pieces of timber making up the perimeter of a wood-framed house’s floor system. A variety of building components come together at the rim-joist area. The rim joist, mudsill, subfloor, and foundation wall converge at this site. This results in numerous gaps and cracks that cause air leakage.
Moisture penetration and air leakage can make rim joists vulnerable to energy loss, insect infestation, and decay. Proper rim joist air sealing can prevent all these issues.
Myron Ferguson, a drywall and building performance contractor, effectively air seals rim joists using Loctite Tite Foam Gaps and Cracks.
Rim joists should be sealed and insulated to the same level as above-grade walls because they are also installed above-grade. Proper insulation is also required as per today’s building codes.
For many years, homeowners and builders have used fiberglass to insulate the interior side of rim joists. Even though this approach is practical in warmer climates, its effectiveness is significantly reduced in colder areas.
Using fiberglass to insulate rim joists comes with two main problems:
- The insulation does not restrict air leakage around the rim joist.
- Fiberglass is air permeable, the material allows warm indoor air to come into contact with the rim joist. In structures where fiberglass insulation is used, an accumulation of frost or moisture is likely to develop around the rim joist area during cold weather. This often leads to dampness and decay, especially along rim joists on the north-facing side of the house.
Addressing air leaks is essential regardless of the material you use to insulate rim joists. Myron Ferguson follows the process outlined below when air sealing rim joists using Loctite Tite Foam Gaps and Cracks.
To achieve the best air sealing results, Myron uses the following tools and materials for the job:
- Step ladder
- Safety gloves
- Safety goggles
- Box cutter
- Vacuum cleaner with crevice tool attachment
- Canned expanding insulating foam sealant – Loctite Tite Foam Gaps and Cracks
Air sealing should be done before installing insulation. Loctite Tite Foam Gaps and Cracks is designed to seal and insulate small cracks and gaps up to an inch wide. It is an excellent option for sealing rim joists because it adheres well to various materials, including metal, wood, stone, concrete, and brick.
Properly air sealing and insulating rim joists is a delicate job. To ensure that the work is done right the first time, Myron Ferguson follows a meticulous process when air sealing rim joists. Here’s a breakdown of the steps:
1. Cleaning the work area. Older houses usually have a build-up of dust and dirt around the cracks and gaps in the rim joist area. Myron Ferguson starts the job by cleaning all gaps, cracks, and openings using a powerful vacuum equipped with a crevice tool attachment. Spray foam easily attaches to clean surfaces.
Ensure the surfaces are also dry to create a strong and long-lasting bond.
2. Removing excess fiberglass insulation. Expanding foam works best when it is sprayed deep into cracks and gaps. It is common to find fiberglass insulation stuffed into the gaps and cracks around rim joists. Myron recommends trimming away some of the fiberglass insulation to create a groove. This frees up enough room to accommodate the spray foam.
Myron Ferguson uses a box cutter to remove and trim some excess fiberglass to complete this step.
3. Applying expanding foam carefully. In the final step of the process, Myron applies Loctite Tite Foam Gaps and Cracks along the openings in the rim joist area. To ensure perfect air sealing results, the seasoned drywall and building performance contractor focuses on sealing:
- Gaps between the sill plate and the rim joist
- Spaces where the rim joist meets the subfloor
- Penetrations for wiring, plumbing, and other utilities
Loctite Tite Foam Gaps and Cracks comes in a compact can that easily fits the tight spaces around the rim joist area. After air sealing the rim joist, you can insulate it using fiberglass.
4. Enjoy the benefits of properly air-sealed rim joists. Sealing rim joists with insulating foam sealant reduces heat loss and saves energy costs. Creating an air-tight barrier on the interior side of the rim joist also helps keep moisture out. This protects the rim joist from rot caused by condensation or frost. Sealing also blocks all gaps and openings that tiny insects and spiders use to enter the basement.
Rim joist air sealing is a highly effective way of improving the energy performance of older homes. Myron Ferguson turns to Loctite Tite Foam Gaps and Cracks when creating an air-tight seal around a structure’s rim joist. This product is designed to ensure getting the job done correctly the first time.
Check out our Where to Buy page to find out where you can get all the Loctite products you need for your next home remodeling project.
Share your own projects