Preperation tips needed for sandstone copings

[PULLMYFINGER]

Hi,

I have an old Victorian house and outside we have the old sandstone style copings with the little stubs of railings after they were cut out many years ago. What is the best way to prep these for painting as I've tried several times using Sandex paint over the last few years and every year it just looks terrible flaking off in patches with green moss/ green vegetation on the sides in some areas. My window revels and sills to the bay and door surround are all the same sandstone but these don't seem to degrade and look terrible any where near as fast. The paint on them certainly doesnt flake off like the copings stones on the wall.

I generally wash with anti fungal treatment to get rid of green mess then give a good sanding / scrapping to remove all loose paint. Then repaint with a couple of coats, but it always begins to flake off after around a year

Thanks

 

[Chrispy6169]

If the stone is powdery or dusty to touch, maybe think about using some stabilizing solution thinned down with white spirit. Or use a pliolite based masonry paint which is self stabilizing.

The only other thing i can think of is moisture. If the stone is pourous, maybe moisture is soaking thru and blowing the paint off when it gets warm