1911 terrace priced well under the new builds nearby, what does the survey not tell you about the real gap

Surveys price the visible and old houses hide almost everything behind lath, floorboards and render. Ours flagged three things and we found six more within a year, all of them consequences of the flagged ones: the failed pointing had been wetting the wall for long enough that a joist end had gone soft, and the eighties rewire turned out to be a partial rewire with the original lighting circuit still buried in the ceiling. None of that is a reason not to buy, it is a reason to hold back a contingency you do not touch, and to open one thing up before you exchange if the seller will let you. The multiplier for us was roughly two on the survey list, and I hear that number often enough that I would plan for it.

Would do it again and would change the order completely. We started with the kitchen because that is what you look at, and then had to disturb half of it eighteen months later when the roof work and the rewire finally happened. Everything that keeps water out and everything that runs inside walls should come first, and every cosmetic decision should wait until those are finished, even if it means living with a horrible bathroom for two years. The money we lost was not on the kitchen, it was on doing it twice.

The honest counterweight: I would not buy that house again, and it is not about money. Four years of weekends, two of them with a room we could not use, and a constant low level negotiation with my partner about whether the next thing was necessary or optional. If you both actively want the project it is one of the best things you can do with your time. If one of you wants a house and the other wants a project, buy the new build, because the survey list is not what breaks people.

On your specific list, the sashes are the least alarming item and the damp is the one to price properly before you commit. Sash refurbishment is well understood, unglamorous, and something a competent joiner does routinely, and you can do them one at a time over years. A damp patch on a party wall could be a failed gutter on the neighbour's side, which is cheap but political, or it could be something structural, and you want that identified rather than described as possible. Get someone independent who is not selling you a treatment to look at it.

Buy the old house if you want the old house. Do not buy it as an investment with a spreadsheet, because the spreadsheet will be wrong and the house will still be worth it or not for entirely different reasons.