So, i have a single skin concrete block garage built on a slab. its been painted inside & out. On one side my neighbour has a concrete slab that is slightly higher than mine. During heavy rain fall the water seeps in via the bottom layer of mortar that my blocks are on, makes that side of my garage damp / wet internally.

My plan is to add a strip of mortar/conrete the length of the side of my garage (7meters), maybe 6″ wide & 4″ high to take the water away from the base of my garage and to direct it to a free draining area.

A run of 7 meters that small is liable to crack / break, should i add a length of rebar? do it in 7 x 1mtr sections? add masonary nails into block mortar for my addition to grip to?

What kind of mix for this? i’m not adverse to a little over building!

Any tips appreciated. Ta

why not just get the neighbour to put a small line of mortar between the slab and your wall? Or paint the edge of his slab and the first inch of your wall with a sealant?

can you not do something on the neighbours side to prevent water ingress? slap a load of vandex or similar on the joint/brickwork to encourage water away. then render over? you are probably unlikely to stop it totally but less is better and easier to deal with internally.

you will always have a wet area unless you prevent water entry. the small hump you propose will get rid of the surface water but the floor would still get damp beyond the bund.