Tim S wrote:
Hi again,

Quick recap - got to make up a floor with about 25-35mm screed. The current
surface is solid, but it's a bit of a "farmer's concrete" special, meaning
it was made with small round pebbles and in a few patches the pebbles are
not well attached. ie they're attached but it doesn't take much to loosen
them.

I suspect if we go digging the less well attached pebbles out we'll get to
earth fairly quickly. No vapour barrier either. I should add, that the
floor's been fine under quarry tiles so I don't see any need to go
replacing it - I just want to make sure the screed gets a good bond.


How does this sound:

1) Soak the floor in a stabiliser.

2) Prime the floor with SBR/cement slurry

3) Screed with 4:1 sand/cement + SBR

4) Paint damp proof membrane on top.

5) Finish (ceramic tile or engineered wood depending on location)

?

=====

What would be good for 1): Liquid SBR? I think PVA will bite the dust due to
the fact there's no vapour barrier.


It may go slightly soft, but it wont dissolve back to liquid.
You probably could combine the two functions of stabiliser and DP by
using something a bit more epoxy resin-ish than PVA.

There are coatings for exterior walls designed to reduce driving rain
penetration.. I forget the name. I'd go that way.



Also, any good recommendations of a paint on DPC membrane?

Many thanks

Tim