Hi all this has been on my mind for a while now ,you know you see the pics off these "Almacen"bases ready for a building, on Estaes Agent sites ,well do these bases have a DPC between the Earth /hardcore/sand ,or is the concrete slab just poured into a wooden frame ? and you put a membrane on top of this then screed ? :P

Membrane????
DPC?????
Dont think the Spanish have heard of either.

Don't think rising damp is a problem here.

If you were starting from scratch with soil floors I would strongly recommend visqueen waterproof barrier I know the locals don't use it, but if you dont use a waterproof membrane you end up with a casa that smells of damp all the time.

Without a dpc you'll find your lovely exterior screed stains up to about 60 cms with damp.  Insist on a dpc extendingoutside the slab and screed off that.            I wish I had !

Sorry, I mean render, not screed.

Does it matter if it's gonna be an "Almacen" ?

Well Bigyin noope woudnt want my tools getting damp would I ;) Almacen just for storing my tools in etc.........!!!I have a nice big old wall just itching for a lean to built onto it ,a poss quick cheapish step before stating on the donkey shed (been nearly 7 years now).
when I did the extention on the side of my house I did hardcore ,sand,insulation, then visqueen turned into interior wall DPC-so if you get my drift when you see these bases you dont see any visqeen sticking out/turned up at sides, just the slab,I reckon there is none, so any damp, up it comes and buggers your floor /tiles what have you :'(

All this damp proofing as only been available in wet old England for the last 20 odd years, they used to use slate ect to stop damp, here in Spain damp is not that bigger problem.
If your tiling and the base is thick enough...should be fine.
Your building a "extra bit" on to the house not a total new-build so you have to live with what you have got ?
Good luck.   

A few years ago I read somewhere about a guy who had built a number of brick pillars using different types of brick and used a damp meter to measure how much damp rose up the columns and he was unable to detect any at all irrespective of brick type.  Whether he was right or not, who knows but the only damp problems I've experienced here are from condensation.
For what it's worth.

Thanks for input guys,Spain is poss a different ball game, but defiantly have it here in UK, in my little bedroom it is steadily moving up the wall all because I have  not got round to putting a lead flashing onto the extension outside ,yet another job to get round to !!!!!
Thanks Phil