you can't because it isn't yours, if your mum is still alive she can have you added to the deeds thru a solicitor, if you have siblings they may object. If you are part owner if anything happens to your mummand there are other siblinmgs you will have to sell it to give them their share of her share and you will possibly get a share of her share. Unless your share is considerd to be the 50% she signs over to you. If u are an only child it is easier. I think.