[bgsavings]

Non-harming is important in Buddhist practice and that includes what is considered to be harmful sexual activity which affects oneself or others, or which is lacking in respect for the feelings of another person.

I don't think the Buddha made any announcements about the specific sexual activities of lay people.

As far as I know there's nothing mentioned about lay-persons masturbation, though it is prohibited for celibate monks and nuns.

However, if it is excessive or obsessive then it is harmful to oneself in terms of over emphasis on sensuality and desire, which in itself may cause dissatisfaction/distress of one kind or another.