Cavity Wall damp - do I treat all internal walls

[teddy bear]

Please advise. My homebuyer's report shows rising damp readings near a chimney breast and in front and side walls of a 1925 semi detached house with cavity walls. Outside it is brick and pointing, no rendering. There is no signs of old DPC or holes for chemical injection outside. There is a mix of solid floors and suspended ground floors.

My concern is that most of the side walls of the semi detached inside are unreachable due to hallway stairs and cupboard, kitchen units etc. Therefore it would not be possible to inject all the ground floor internal walls, hack off plaster and fix damp proof membrane against the walls. So if I can only treat a portion of internal walls, would the untreated internal walls bridge/breach the damp proofing of the treated walls?

I also do not know if there is debris in cavity wall causing damp and if there is insulation, cold spots with wall ties etc.

I do not know if the solid floors have dpc.

The top chimney stack has been removed/capped and new roof built over capped top. Surveyor recommends chimney vents.

If there is a concern that not treating all the internal walls affects the DPc of the rest, shall I walk away and not bother paying for a damp survey? What are approx costs?

 

[Wayners]

I think you need to get a damp survey done with a written spec to put right.
Then you can get costings for work