Air sealing the gaps found in wall top plates

[SIM]

Top plates are often the cause of huge gaps in the thermal envelope of your heated home or business. The gaps are created when the lumber dries and shrinks over time. As a result the top plate pulls away from the wall tops stud (top plate). This gap can only be seen from the inside of the wall or by looking down on the top plate from in the attic.

In this video you can see that their exists a gap of about 1/8th to 3/16 inch between the wall top plate and the plaster surface. Unfortunately, heat that moves into the wall cavity will have a clear passage up and into the cold attic 24 hours a day during the cold months. An 1/8 inch gap multiplied by 200 interior and exterior wall feet for a small 1200 sq ft ranch is equal to a hole 5 inches tall by 5 inches wide, or 25 square inches. Imagine all the heat that is flowing out 24 hours per day!!!

The typical way to stop this air flow is to seal the gaps from the attic. This can be done inexpensively with a caulk gun, or much more quickly with 2 part spray foam. If you plan to do the work yourself you can save by using caulk. Sometimes exterior wall top plates are difficult to reach. It is nearly impossible to caulk the top plate seams on a low pitched roof from the attic. One solution is to remove the soffit boards and spray foam the top plate from the outside. Another solution for exterior walls that are empty would be to dense pack the walls with cellulose. Cellulose acts as an air sealer so even if gaps in the top plate exist, the cellulose will pack and fill the gap during installation as long as you are using the dense pack method.

[adam12]

I tried caulking and it is a terrible job. I strongly recommend spray foaming with 2 part foam. Some people may think a can of foam will work, but that is 1 part foam and does not seal/stick as well, especially if their is low humidity.