Help needed with waterproofing shed

[Day]

HI, I need some advice in trying to waterproof a brick shed build on concrete slab. I've got no experience of any of the waterproofing materials so I need your advice. Recently more and more water is seeping into the shed after heavy rain. The shed was build about 5 years ago but it hasn't been done correctly. The concrete slab was poured into a ditch lined with waterproof plastic lining but it looks like the soil level is above the level of the slab and the lining. It's not possible to access 3 of the sides of the shed in order to correct the soil level. The walls are build on top of the concrete slab out of single layer of bricks. There is a waterproof membrane between the first and second layer of bricks. The door frame sits on top of the first layer of bricks and above the waterproof membrane. The water seems to be coming in between the concrete slab and the first later and no moisture rises above the waterproof membrane. As there is no access to 3 of the outside walls I want to waterproof it from the inside. Originally I thought of painting the floor and bottom of the wall just with some waterproof substance but wasn't sure if that will be enough. So then I was thinking of maybe painting some kind of waterproofing substance onto the joint between the concrete slab and bricks up to the waterproof membrane, then lining the floor and up the sides of the wall with plastic membrane. Next I would pour a layer of concrete up to the second layer of bricks. That will raise the level of the floor above the outside level so no more water will be pooling on the new floor. I was thinking that the waterproof lining membrane and the waterproofing substance that the first layer of bricks are to be painted with should be bonded together to prevent water rising through that gap.
What do you think of this plan? Will it work? I'm not worried about loosing 10cm of height internally. What waterproofing substance can I use? Maybe something that stays sticky so that the lining membrane stays stuck to it like the tar they put on flat roofs.

Here is a drawing of what i was thinking of doing

 

[theprinceofdarkness]

I would not pour any concrete over the floor as it will make any further remedial work impossible. Wait until the floor dries out a bit (August?) Then tank the lower inside with a SBR/cement slurry. Use 4 coats. Then keep your fingers crossed. The SBR finish is rugged enough to walk on but should be protected against heavy stuff being dragged across it. So if you store car engines in the shed put down a loose floor of OSB.
Frank

 

[Day]

Thanks for the suggestion. What proportions of SBR + cement to mix? Does it need sand as well or just cement? Is it suppose to be a very runny mix? How would I apply it?

 

[theprinceofdarkness]

It says on the container, 50% cement from memory. It goes along way, 5 sq m /litre? I use a small stiff polypropolylene brush because you have to work it into the surface of rough material. It has a fast initial set so don't mix up too much and have a bucket of water handy to clean the brush. If it sets the brush can only be cleaned by hammering the bristles.
Frank

 

[^woody^]

SBR is not a water proofer!

You can lay a standard polythene DPM, and tuck it into a joint.

Or get a bitumen product from the likes of Wickes, or something like RIW or F-Ball Stopgap F75, F76, F77 or F78

You can lay a chipboard wearing surface instead of screed.

The problem you will have is water soaking in the wall and running down and across at the floor level. So consider an external water-repellant coating to the walls.