Rotten problem seeking good solutions

Maintenance

I have a terrible problem with what I think is dry rot under the floor of a 2 bed terrace.

9 years ago we replaced half the foor joists, treated all the timber, fitted a couple of air bricks and then what?  It got into the plaster of the walls.  And now we pull the floor up and the new joists are badly infected.  

I am fairly knowlegable about building work and my builder is a superb general builder.  We have sucessfully tackled many damp problems and al sort of structural issues over the 20 years we have worked together but we have clearly failed here. 

I am looking for a specialist surveryor, watching all the videos on U tube and all the treatment guides on the market.  We are also considering the nuclear option of putting in a hard screed floor.  We have done this elsewhere and the insulation really boosts the warmth of the house.

Any experience?  Any suggestions?  

The only thing I can think of is the 2 air bricks fitted at the front were not enough.  Ventilation is relaly important for avoiding rot.  And the house next door is delapidated long term derelict....