Triangular fillets of cement mortar can crumble and allow water to penetrate. Gaps may appear where the flashing has come away from the brickwork. Use a cold chisel and club hammer to remove the old mortar. Repair the defective area with a 1 : 3, cement ; sand mix, adding a little PVA adhesive to help it bond to the remaining surface. This will give a satisfactory seal, but for a more permanent seal use bituminous mastic. This can be applied directly from the tin using a builder’s trowel or can be applied with an applicator gun.
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