The smooth cement floor is about 200mm below garden level
especially in winter there is a fine layer of moisture on the side of the floor that is next to the garden facing internal wall.
Damp occurs in an area of 3 ft from the internal wall
Other wall is joined to nxt-doors garage & there has never been any damp
within seven feet of that internal wall.
During summer there is white salt marks on side of floor nxt to damp wall.
Internal wall has damp @ a height of 3ft as you walk in from the garden( white salt marks more evident in summer).
Then damp slowly tapers down as you walk away, 8ft from entrance to a height of 1 1/2ft.
The cement on wall becomes very powdery, floor cement notso it is all in one piece no powdreing or cracks, just surface water.
the white stuff is salt crystals forming on the walls technical term is effloressance.
The problem is the soil against the garage, any soil against the wall will cause damp and will creep along the wall.
As the post above says, get the soil away from the wall. Go to the DIY projects section where there are about 10 projects associated with damp proofing of one kind or another. Every bit of advice, plus tools, products and even a free advice number can be found there.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!