Water ingress on door threshold

[Smoo91]

Hi all,

Just moved into a house and noticed a damp smell near front door. Currently just boards with mdf on top near front door.

Pulled this away near door and saw water on boards. Removed old tiles from threshold near door and concrete threshold was very wet. Large void under door.

Dried all this out and filled crack in concrete but becoming wet again very quickly during rain.

Any suggestions on how to tackle this and make it all water tight?

Thanks.

 

[Wayners]

Masking tape leave a gap. Inject polymer. Something like CT1 or 0b1.
Pull masking tape off. Finished smoothing.