If you live in a community property state, community property is property acquired during marriage.  This also applies to income during marriage.  Each spouse has a one half interest in the community property.Separate property is property acquired before marriage or after the marriage ends.  This also applies to income before marriage or after the marriage ends.  A spouse has no claim to the other spouse's separate property.You purchased the house before marriage which means it is your separate property.  However, since your husband is making payments on the mortgage during marriage, those mortgage payments are community property.  Therefore, your husband would have a one half interest in the amount of those mortgage payments.  For example, if your husband paid a total representing 20% of the mortgage, he would have a 10% interest in your home representing his share of the community property represented by those mortgage payments.  Yes, he is building equity.  Also, if improvements to the home are made during marriage, those improvements are community property and your husband would have a one half interest in the enhanced value of the home those improvements represent.If you don't live in a community property state, other rules may be applicable.