Several years ago, I built my house on a piece of land owned by my sister. When I decided to sell the property, I discovered that my name was not on the title deed. Is this normal ?

Yes. Under French law, the principle is that ownership of the land includes ownership of everything on and beneath it (Article 552 of the Civil Code). This means that even if you financed the construction of the house, your sister remains the owner. For the house to become your property, your sister would need to agree to give or sell it to you.