Oakum and lime mortar, gap-filling the breathable way.

This new accoya window with heritage double glazing going into Ian's new bathroom. Bought a new 4kg bale of oakum today, so soaked it in Natural Hydraulic Lime 3.5 slurry, bedded the window and packed it into the gaps, topping off with NHL3.5 mortar pointing with the tuck trowel. Wet hessian to cover; lime mortar needs to dry slowly. Proper job!