Darren Naughton

Hi everyone. I have recently had a shed built 5m x 5m square. It is made from shiplap tanalised treated wood, heres the issue I have had a small leak on one side from driving rain pushing it's way through the small gaps in the interlocking joints. Unfortunately I am no longer able to contact the constructor of the shed so I'm at a loss of what to do. I have used a multi purpose sealant from a gun tube at the ends of the lengths to try stop the water gaining entry into the corners were the water is leaking internally. I was considering going down each length and filling it with something to stop the water coming through but this will not only cost a fortune but look unsightly. Is there a tantalising paint that I can use to seal the gaps and also aid in reflecting water but I know this is probably not possable a paint that will also allow the wood to breathe as i dont want internal condensation. The wood is definitely tanalised it has a light green tinge to it and 4 months old. Any help on this would be very much appreciated. Thanks Mr D Naughton