We need to add ventilation holes to an existing building. The holes will be core-hole drilled through a limestone brick wall. The bricks have crevices. The contractor is acting stupid and obstructive or I would ask them. How would one mount a short (24 cm lond, D= 300mm) piece of round air duct into the core hole? Simply put in? Sikaflex all around? How about risk of moisture creeping in?
My first idea is to let the duct sick out 1 cm on both sides, and to grout the wedge with sikaflex. Criticisms? Better ideas?