Cold air, rodents, and insects commonly intrude into wall cavities through large and small gaps near the foundation.

Sealing the foundation can greatly increase the energy efficiency of your home and reduce damage from pests.

A small cost for materials and a day of hard work can give you big long-term benefits.

Foundation sealing outside

• The drawing shows the location of a typical exterior foundation gap.
• A hand mirror can help with inspecting and cleaning out the gap with a stiff brush before sealing.
• Use 100% exterior silicon caulking to completely fill the gap in places where is it less than a half inch wide.
• Push the tip of the caulk tube as far as you can up into the gap and completely fill it with caulk.
• As needed, press the bead of caulk into the gap with your finger. Frequently wetting your finger in a bucket of water will keep the caulk from sticking to your hand and make it easier and quicker to get a good job.
  
• Clear caulk will minimize any visual effect. Masking below the gap will make a neater job. Kneepads will help.
• For gaps larger than a half-inch use low expansion spray foam insulation. Be certain to get spray foam insulation that is rated for exterior use.
• Push the tip of a Pro Type spray foam dispensing gun as far into the gap as possible. Trim off the excess foam after it has fully cured. Mask the surface to minimize stains.
• Check and seal the foundation gap of any garage walls that connect with interior living space.

Foundation sealing inside

• Cold air, insects, and rodents can gain access to wall cavities through air leaks from the interior side of the foundation.
• The drawing shows three places caulking can be applied near the inside of the foundation to effectively eliminate all air gaps and access by pests.
• Locate and seal all plumbing and electrical penetrations. Use low expansion spray foam insulation for holes larger than one inch.
• Much larger holes may require blocks of insulating foam board that are cut to fit and then sealed in place with spray foam insulation, as described on the DIY Attic Insulation page.
• Use a good brand of 100% silicone exterior caulk for interior foundation sealing.

Summary

• A day of hard work and a small investment in materials will give you much higher home energy efficiency and greatly improved protection from pests.