It's not really my field (pun not intended). I'd have asked the surveyors today, but I'm stuck at home medicated to the eyeballs on painkillers. And I wont now see them till end May.

Historically from what I'm told and have seen, the "rules" regarding raising buildings on land NOT declared as urban WERE (in the past,and from all accounts not too far distant past) often dealt with lightly esp if the landowner was local and known. And things like access rights occasionally blatantly re adjusted/removed/added occasionally too. Some areas worse than others.

It's all VERY MUCH in the public eye now - and as records centralise more and more - the tiniest indiscretion leads to fiscal/political disasters. Several assessors in Madrid city have been pilloried for making incorrect assessments (in return for money of course) - Malaga still lives with its alleged indiscretions.

We had a old friend (ex Spanish General, now passed away) who had a house on a supposed double plot with well etc, apparently on the edge of an established estate. However (and this is a while ago now) when he attempted to build a second home on the other half (second plot) for his son - it was discovered that it had never been urban land. In fact was illegal. I'm sure in the past given the old mans status - it was simply assumed that all was above board and maybe nobody wanted to "suspect/criticise" one of Francos generals either. I doubt, having experienced his way of doing things, he did it wilfully. The existing home was legalised - but the other half plot was declared rustico.

There was a case on Madrid local TV where a a long standing stable block(shack) on a "finca rustica" had been repaired/rebuilt and a small shelter for the workers added. This on a HUGE estate - well above 10,000 - well above 100,000. In went the bulldozers. Had they just left it and just added a plank or two to keep the wind out - it would still be there.

Seen folk come into the town hall attempt to rebuild places - but as the work would be classified as OBRA MAYOR - it gets rejected. I have been told one case was accepted before I joined but because the incumbent actually lived there surrounded by his cows&goats and had for 20 odd years.

If the land is OK for building (say there is permission for a farmhouse etc) you may still huge problems with amenities - Water/sewage/electricity/phone etc. I was really quite surprised recently to visit a friends new house on a small ( & legal ) rural estate just into the province of Avila. No sewage (and the streets are so narrow and poor surfaced - god knows how a truck will get in to drain theh septic tanks) - No street lights - no refuge collection except from one central point once a week - I'd hate to live close to it in summer. Very low max electricity supply - simply the wires wont allow more - inconsistent and low water pressures - He works for Telefonica so was able to get the phone bit sorted quickly - but out in the sticks if there are no free circuits on the trunk in your area - you are in for a LONG wait.

Also (if my wife is a good example of an average Spaniard) - Living out in the sticks is not high up on the wish list. She's very unhappy in pitch black - I quite enjoy seeing by starlight. And you'd be dumb to attempt to have one over the limit and drive home now. 10 years ago - if the local police stopped you - you could get away with a warning (I have done!) - now - BIG HASSLES.

Basically - if you see something you like. Get the details and get to the town hall. But unless the municipal assessor (and thereby the town hall) ratifies in writing a request to build/rebuild/renovate etc - I'd always assume that the answer will be NO if I were you.