Damp problems - rubble and solid walls

[JackieA]

Edit - there's dpc on the extension, but its above inside floor level :-/

Hi all,
I posted a while ago about a property I was buying and its damp issues. Well, I now own the house, hurrah! I knew I had my work cut out and I love the house so no regrets, but having pulled off some plaster my damp plan might not work, so can I get some advice please?
Its a 1800s end terrace cottage, the gable wall is a rubble stone wall and the other walls are solid brick. It also has a single story 1960s extension on the back.
The main part is below ground level and obviously no dpc. The extension doesn't seem to have dpc (render chipped off at the bottom so I can see), but that's also at/below ground level anyway.
So my question is, how best to prevent damp and ideally insulate it please? My plan was:

1. Dpc cream injections above ground level.
2. Tank inside up to dpc.
3. External insulation down to dpc line.

But, looking at the rubble wall and the state of all the the pointing I'm not sure dpc injections is an option. Luckily the cottage has a good head height so raising the floor is an option if needs be, although head height in the extension part isn't great so I'd prefer a step up to the original part inside if that's the way to go (and tanking the extension part), if that's possible.
By the way, all the walls are wet, not just 1m up. Also the roof needs completely replacing and I suspect a downpipe which is going into the ground may need moving (it appears to go into a drain though). There's external render already which is painted and flaking which I guess is causing the penetrating damp issue.
I like the thought of external insulation having read a lot about it, but I'm not sure if it'll be suitable without a dpc or if dpc injections fail.
So any advice please? I'm getting professionals in for this part of the renovations, but would like to get some unbiased opinions first please so I can weigh up the options.
Can post pics if it helps
Thank you, and sorry for the long post!

 

[Footsoldier888]

If you don't have a full structural survey as a starting point I would pay for a builder who has done previous work on old buildings to come round and do a report on what needs doing.

Avoid any of these free damp surveys like the plague, in the wrong hands dpc and tanking will just make the situation worse.

A cctv drain survey might be a good idea too.

Possibly all the render might have to come off in order for the walls to dry out.

HTH.

 

[JackieA]

Thank you, yep that helps. There's plenty of old properties in the area so I'm quite sure an experienced builder would know what needs doing, like you say it's the damp companies I'm wary of taking advice from :-/ one of my friends in the trade said they'd got a company in to do dpc injections on a rubble wall for the guarantee they offered, and when it failed and they got them back they wouldn't remedy it as they said there'd been a 40% damp reduction which constituted a success to them!
I just want to do the right thing, we love the house and want to keep it for many years to come

 

[StephenStephen]

I found this book extremely helpful:

Jonathan Hetreed -The Damp House: A Guide to the Causes and Treatment of Dampness

 

[bobasd]

nock off all failed an damp plaster an outside render back to masonry. then post pics showing what youve done. show esp at floor or ground level an any chimney breasts