If things are going to change to the extent that even a buried duct is likely to be disturbed, how about overhead? At least it can then be seen and avoided (or seen and moved).

AFAIK creosote (i.e. solvent/coal-tar based) preservatives are a known problem (not that you can buy it any longer) - I've not heard of problems with water based ones (but then absence of evidence isn't evidence of absence). 

   - Andy.

Alan B said:

small chance drilling will trigger cracks in the wall

Been there, done that! Drill a hole and next thing is that you need to re-lay a couple of courses of bricks (which were not laid well originally).

I am sure that there are constraints which have not been mentioned, but one option is to rebuild the wall first. If that needs to wait, then the run of SWA could be regarded as temporary and accordingly, deterioration due to preservative, or rose fertiliser, or pesticides, etc. might be acceptable.

Like Andy, I doubt that water-based agents will be a problem (save for ingress), but could you ask the manufacturer?

Thanks for your thought and concuring with my view that water based wood treatment is OK. I am considering this as a temporary isherwood install, but aware 2 year projects often turn in to 10 year projects.

Looks like there is probably 100k in work planned, not sure how we'll customer is positioned to fund it.

The wall I would be clipping to is 6ft high, 10m long. Something like a 4 or 5 inch bow in the bottom. No weight against it, the building next to it has had subsidence. If I clipped near the top there would be less stress on the brick joints. I was thinking of closer to the bottom, where I assume the joints are under tension from the warp.

I think I will stick with going along the fence as it should be good for at least 5 years and about half the cost

Bit late really but I concur, fence will be fine - perhaps if they want to coat it with something let them do that before the cable goes up. Better to be able to see it...

Even the old Creosote was OK once it had dried off, the problem being it stayed active as a solvent that comes off onto almost everything including hands and clothes for several weeks after application. For the same reason attempts to paint over it were unlikely to be perfect.

It was most destructive of the older rubber covered cables - from memory PVC stains, but does not degrade noticeably faster - plastic twin and earth clipped up in creosote soaked wooden barns and so on lasted quite well - sunshine and rats were more of an issue.
Mike

I would avoid ANY disturbance to the wall. That leaves as options either clipped to the fence or run overhead. On the fence, though a departure from the regulations is in my view acceptable in this case.

I have never seen cable damage from water based timber treatments.

Or what about a weatherproof 32 amp ceeform socket outlet on the outside of the house and an extension lead in 6mm HOFR flex.