Renovation nightmarethe

[lostinthelight]

We have taken on the renovation project of an old stone built house that was extended in concrete blocks in the 1970's .It now needs extensive work again as the cement render has blown and cracked on the exposed south and west elevations (710ft above sea level)
Inside is not going to be a problem but what to do to the outside is proving to be a bit of a headache .The blockwork of the extension and above the old stone walls been blown rockwool filled as we can see filling holes since we had some of the blown render removed .
My OH has been chipping around the lower stonework and it looks as if it may be worth pointing up as a feature seeing as that part was built in the 17th century, weve uncovered a lovely inglenook fireplace with oak lintel in the lounge.
So any advice/bright ideas as to what to do with the outside prep and finish would be apreciated ?.
thanks
litl

 

[cjard]

Not sure I'd want to live in a house that was lovely stone for half its facade and a 1970s concrete mass for the rest.. But taking down the outer skin of he extension and replacing it with a similar stone probably isn't an option so I dare say my opinion would be to render it all.
Perhaps making a feature of the window near the door, cutting across from the roof of the porch til the edge of the original house and then down.. All that as feature stonework could work out (and if it didn't, it can be covered again)

Is the original house solid wall? I ask because you may need to address potential moisture issues within the wall if you do re-render it (or indeed if you leave part of it exposed); using a render that didn't breathe could see it failing in future due to accumulating moisture in the wall. If the mortar between the stones is lime it will be quite porous/breathable - pointing with a cement mortar will cause problems. A chemical water proofing agent that is still breathable would probably be better, but I'd take specialist advice on it