Dry rot - help!

I'm new to this site but had read lots of useful information so hope you'll be kind to me1
I bought a 1930s mid terrace house in 2004 and since then, I have had four outbreaks of dry rot. The first three were done after the initial guarantee but the last one is in an ever so slightly different area. Each time, the company that I have used (same one each time) has proposed to : remover skirting boards and plaster to 1m, introduce fungicidal biocide into a network of holes, steralise surface masonry and replace with treated timber (and install new chemical damp proof course). However, from what I've read it seems that the cause of dampness needs to be treated if the dry rot is going to go away. My fear is that, the new outbreak gets 'treated' and then a few months later it reappears somewhere else in my house.
Under the concrete floor could there be a void that may be letting in moisture? If so, what do I need to do? If I go away for a day ar two, I do notice a musty smell in the downstairs of the house, which indicates there is some sort of damp problem!
Apologies if it sounds like I don't know what I'm talking about - that's cause I don't!
But this problem has been going on for 4 years and I can't face much more of the financial and emotional burden that it's become!

Your mistake was to continue to use a company that did not sort this out the first time.

When treating dry rot, the affected timber is replaced, plus some adjacent timber, the masonry structure is sterilised in a wide area around the outbreak - including replastering, and the actual cause of the dry rot is rectified - ie ventilation.

You need to get a proper survey done - or get several of the treatment companies to investigate and quote for remedial work to cure the problem and the possible cause of any future outbreak.

And you should have got a 20-30 year guarantee on the initial work, so I would check that guarnatee carefully to see if you can claim of the companys' insurers for this current outbreak.

Thanks for your quick reply!
i did get a guarantee for the original work but the company claimed that this latest outbreak could not be proved to be from the original one.
This time I am getting them to excavate a small section of the concrete floor to see what lurks beneath!
I recognise that I should have got more surveys/quotes but you learn from experience.
If this latest work uncovers more problems I will then look around for other companies that can offer quotes - does this sound like a good idea?

Of course they would deny that the new outbreak is connected to their previous work.

I'd beg to differ, and unless later outbreaks were at the opposite side of the property, then there would be good odds on you winning any claim against them.

Get a different company in for a different opinion, or a professional independent survey done - including comment on the work done previously and initial quote/survey from that company.

And if not done so already, lodge a claim/appeal with the companys' guarantors while getting some more advice. Your home insurers may be able to help with free advice.

I'd be wary of this company being competent to do the work properly now, if they did not do it properly the first time

lets hope it isnt in the concrete floor,which makes me think they really dont know what there doing,they shouldve checked to see if theres any evidence in the floor if its near the original area,if you have cavity walls theres no point in installing a dpc unless they have said they are going to be clearing the cavities and investigating the true source of the damp,with dry rot you should expose and treat 1m past the last found evidence in all directions and replace any timbers etc(where feasible).as woody has advised i would get a few more surveys done and perhaps ask the original firm if they are backed by a governing body(used to bwdpa) dont know what its called now?to see if they can offer any help.