Active job

Sort out water ingress into metal shed

We have a skyline type shed / garage which is like 20 years old sitting on a concrete base. After heavy rain we find a big puddle of water in the center of the concrete base. Initially we thought it was from couple of small leaks in the roof but even after they've been fixed by a professional roofer it is still occurring. The odd thing is the flooded bit is in the center and the surrounding concrete base and the overlying roof appears dry. We need someone who has experience diagnosing and fixing this problem. Due to the intermittent nature of the problem We would prefer someone who can guarantee their work.