My concrete shed (workshop) base floods

[Richard_C]

Lots of good ideas. I would start with an umbrella and go stand out there in heavy rain and observe very carefully for a while. The water might be running down the wall, running down the far wall and under, or???. Watching the puddle form might help decide which problem(s) you have to solve.

Hire of bottle jack's has been mentioned, not sure how short they go. If you have a car, you have a scissor jack. If you have helpful neighbours you have access to many.

Back in the day, when I lived in a Cheshire village, well liked elderly neighbour Bill needed help with a sinking summerhouse. We had a Saturday go at it, his neighbours with our jack's and crowbars, lifted and put concrete posts under with some gravel in places. Mrs Bill arrived with tea and cake after a bit and the job was done. Maybe you could get friends and family round for a fun shed-lifting party?

 

[Titan_uk]

How about a garage door sealing strip 'the wrong way round under the edge? Instead of the flat bit against your door you'd have it against the bearers, properly sealed under the strip and against your bearers hopefully would do the trick.

https://www.ebay.co.uk/p/2255568440?iid=332458514794
I did it to a playhouse using a stormguard bright yellow one and I kinda like the yellow stripe all the way around