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Sunroom Leakage Repair #2

Bedroom sunroom has high moisture and possible leakage through windows, exterier is plaster and windows are single glazed. We've seen some water leaking inside sunroom during heavy rain and upon checking found that its thorugh some joiner or may be crack somewhere and through that water is sipping in. We got the small gib removed and checked as shown in the picture and left it open for further check. So , I m looking for full repair of this issue and waterproofing and weathertightness of sunroom.