Ethafoam is a closed cell, flat, sheet foam that can be used between log courses with flat-on-flat log construction. This allows for a 1/4" caulk joint.  Ethafoam MSDS

The Gap Effect: How Logs Dry
When using sealant tapes like Ethafoam, it's important to caulk between logs, especially if the logs are green. Pictured below is an extreme case where chinks have opened on the sealant side of both logs. In this case, the 1/4" Ethafoam isn’t enough to fill the 3/8" to 1/2" space between the logs, leaving the area vulnerable to insects, water infiltration, and driving winds. Caulking or chinking the outside gap will minimize problems like this by stretching and protecting the area as the logs continue to dry and shift.

The gap effect with ethafoam

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