On Tuesday, 5 July 2011 07:43:14 UTC+1, Lobster wrote:
While fixing up the workshop, I've painted the bottom 18" of the back
internal wall with Aquaseal black bitumen paint in an effort to prevent
damp coming through (the construction is slightly complicated to explain
- the bottom of it is a concrete pad which is next door's [somewhat
higher] ground level, so it's a bit susceptible to damp).

Anyways, next up will be to paint the rest of the walls and floor, and
I'd quite like to overpaint the bitumen area at the same time, just for
cosmetic reasons. I emailed the mfr for recommendations on what to use,
and was advised: "our bitumen paint range cannot be over painted with
any paints that I am aware of as they bleed oils when heated up. The
only way to find out would be by contacting a paint manufacturer as they
may have something that we at Everbuild are unaware of".

So, any suggestions?! Do we reckon stain-block paint would do the
trick, or is bitumen paint too much for it to handle? I don't want to
waste my time overpainting it if it's going to bleed through anyway; it
would look worse than just leaving it... it's only a workshop after all!

Thanks
David

I gave some bitumous paint several coats of PVA and then painted it.
Was OK for ten years at least.
If there was positive water pressure behind it, you might get flaking off.