18:24 Jul 26, 2011 

Thanks Alex, that makes perfect sense, unlike and as you say, the original massacred text. I´ve put in "where the ground floor is not included in the numbering of floors". If you want to post it as a reply, please do so and I can give you points. Best wishes. Sian.

17:37 Jul 26, 2011 

Notaries are well know for massacring the language, what they are saying here is that it is the "Piso tercero primera" which is an abbreviated way of saying "The apartment on the third floor, first door", they then say "en la Planta tercera de piso" which is a bit redundant as they are saying it is the third floor again, but the distinction here is the "piso" which in this case means "above ground" , then when they say "o cuarta de la casa" which would be "or fourth of the building" they are referring to the fact that it is in fact the fourth floor of the building because it has one floor below ground.

So basically this is saying:

"The apartment which has its entry through the first door of the third floor of the building, if only the floor's above ground are counted, or the fourth floor of the building if all the building's floors are counted". Now how to say this in "English" I leave up to you.