Abstract: A combination sill sealer and flashing for use in wood frame construction to provide sealing and insulation between frame sub structures while accommodating shrinkage and settling of those substructures as the lumber drys. The sill sealer and flashing comprises a sheet of flexible material that is vapor permeable and liquid impermeable along one long edge of which is formed a longitudinally continuous channel in which is disposed a contiguous length of sealant material. The sealant material may be a rope of polymeric foam, a curable silicon, or other synthetic rubber like material which is resiliently compressible and retains its pliancy over time and under a wide range of temperatures.