When I installed this sliding door, I foolishly put it straight on the slab thinking exterior sealant would be sufficient to keep water out.
Unfortunately it’s not…
Every time it rains heavily I get water creeping underneath it or collecting in the track and then seeping through.
Is there any waterproofing fix you guys can think off, that doesn’t involve taking the door (frame) out, shaving some of the header above it off, adding a sub sill and proper flashing tape underneath the track?
Also, would some concrete crack filler be sufficient to prevent water creeping through the crack in the slab?
You could try concrete crack filler, but concrete is porous. I would recommend a concrete curb that would help to push the water off to the edges. Water will take the path of least resistance. You just want that to not be into your shed.
You could spray water on it with a gardenhose to see where it's leaking. If it's really coming from under the frame there's this stuff called tixophalte caulk, this is meant to be watertight.
Yeah, I put lots of silicone underneath the track / frame too.
The slab was meant to slope away but that got lost in translation with the concreter and as a result has been poured dead flat / level, which doesn’t help of course…
I was thinking I could cut a grout like drain channel 2-3cm away from the door to lead some of that water away from the door.
It seems like the water is probably getting higher than the sealant. At that point, it's almost certainly a manufacturing thing with the door that you can't easily fix. A sill would be the best bet imo.
Without a real sill and a slope on the outside your going to have water intrusion.
Add a gutter/diverter above the door on the roof. Remove all the sealer you can. Use waterproof concrete sealer/paint on the slab. Fill every gap you can with silicone. Shave down the slab with an angle grinder to add some kind of slope.
If the concrete applier 'forgot' to add a slope to the outside see if they will help with the remedy.