Water spots on concrete floor of new shed

Hi all.
I am looking for advice. We recently got a new shed from steeltech.
We had a foundation put down by a local builder. Shed was installed and the builder came back to lay dpc and concrete floor..we let the floor dry..and a few weeks later after heavy rainfall I noticed wet spots on the floor.
I was concerned water would be getting in via roof.. but no. I put a cardboard box down under where the spots were happening and next day, face up box perfectly dry..damp patch worsened and bottom of box wet.
We contacted builder ( many times)
Since then. The floor is worsening after any rainfall. I can only assume the dpc was not put down right. ( the foundation seemed very solid)
Last rainfall last week. Damp spots all over the concrete floor. I am concerned with winter drawing in out new She'd could be ruined with damp.
We have not put anything in it as it will get destroyed. builder eventually looked at it and said he will put membrane or filler around the sides of the shed and some kind of coating on top of the shed floor.
I am a bit dubious as I trusted him to lay the floor correctly ( it transpired that he used 500 dpc not 1200)
He is also delayed and delayed responding to us. Am I just better of hiring a new builder to fix this? I would prefer to do that rather then a shoddy fix? Or is this an OK way to fix a concrete floor letting in spots of water?
I tried to post a photo but couldn't.

Appreciate your advice.

It could be condinsation coming from the roof .

Sounds as if the builder knows the dpc is faulty and is proposing mickey mouse solutions - he should dig it up and do it properly at his expense

Pinoy adventure said:

It could be condinsation coming from the roof .

Click to expand...

The walla are finished with some kind of anti condensation material.. I put cardboard down to see if the drops were coming from the roof. The facing up side of the boxes were dry and the concrete floor and underside of boxed is getting wet.. its definitely coming up from the ground

Have you been inside the shed during heavy rain? Is it possible that a leak through a roller door or wall sheeting is finding the low points of the floor and an hour later has dried back to few puddles?

Can you put a damp membrane on the existing floor and put a screed on top, this will raise the lever about 25mm but it shouldn't matter for a shed