the word "flood" conjures up images of large amounts of water (like covering the entire fllor and risiing up the walls). Is this how much water you're getting? You state that it happens "everytime there is a heavy rain". What's a heavy rain? Total 1 in.? 2 in.? 5 in.? Downpour? 1 in./hour?

The sighting of the leakage with respect to the rain is important. If you getting water on the floor right after the rains start or during the rain event, then it's likley surface run-off. If it doesn't start to leak until a significant time after the rain starts, it may be the groundwater table rising.

There has to be an entry port. Does it start in one corner and grow? Is the room carpeted so you don't see it until the carpet is saturated?

Until you define the source it is impossible to recommend a corrective action. If you don't know where to start, I would call a local waterproofing contractor and have him on notice, that the next time it rains enough to leak, you would like him to come and see it. Then, take it from there.

hope this helps.

I love in Florida and recently purchased a home that also floods when the water table rises. Mine won't flood at first it takes heavy rain over 4 inches. It seeps in from two corners on the outside edge of the converted garage. I'm now looking into a sump pump and treating it like a basement. I was wondering what your solution was?

if it seeps in when the ground water table rises, where is your sump pump going to pump it to? Souds like you either need to regrade and get it higher or waterproof the exterior so it can hold the water back until the groundwater level recedes.