I am planning to replace a rough single storey wooden flat roofed extension built on the boundary with a three storey well insulated extension with a hipped roof. One wall with no openings and not supporting floor joists, they run the other way, is on the boundary replacing the existing wall. Unfortunately there is a large garage in the neighbours property which comes up to within 200 mm of the boundary making construction extremely difficult both for foundations and the wall. Space at this point is in short supply but a SIP wall could be constructed and finished up against the house and craned the 2 metres into position if this is practical. However the small gap between the existing garage and the new wall would prevent any further finishing below about 3.5 metres. There is reasonable access to the two ends and those walls could be either SIPs or conventional. This would also allow the corners to be correctly finished.