Where the damp course should be at the bottom of my outside house walls the paint flakes a bit because of the damp.

 

I want to put a course of outdoor tiles, is there a product I could use first to seal the area before tiling?

I would scrape back to bare concrete, then apply an acrylic resin primer like JBP Contact-F Primer.

 

We had some rising damp at our home but none at all since I applied a few coats of this primer, followed by a couple of coats of a good quality external paint like Dulux Weathershield.

 

In your particular case as you are going to be tiling the area, a couple of coats of this stuff should do.