If a wife voluntarily gives part of her wages to her husband to help him build a house for the family, can she later insist that her name is included in the title deed to the property? And if the husband offers to write a will so that the property passes only to her and her children will that be correct under Sharee'ah?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If this woman had gifted her money to her husband, then taking back the money is forbidden, for the saying of the Prophet said:  "A person who takes back a gift is like a dog eating what it vomited." [Al-Bukhari and Muslim]

If she had presented the money intending some benefits in return then it is allowed to ask for the money to be returned. Thereupon, she may ask for her share in the house.

As for the will of a husband that the house is for his wife and children, though this will is valid but it cannot be enforced except with the permission of all inheritors. The Prophet said: "Allaah has allotted every person who has a right his right, so there is no will for an inheritor." [Abu Daawood]  In fact, the wife and the children are among his inheritors.

Finally, we draw the attention that a husband is allowed to grant his wife and equally among children a portion of his house or other belongings as a gift. The preponderant opinion is that allotting gifts equally to one's children and not preferring some children over others without any Islamic reason is an obligation.

Allaah Knows best.