In conjunction with National Preservation Month, the Lyman Estate will be the site of a workshop series for enthusiasts and owners of historic homes on Tuesday nights throughout May. The first event is “Architectural Styles in Waltham’s History: From the 17th Century to the Present’’ on May 8 at 7:30 p.m. It will be presented by Jack Cox, a Waltham High School history teacher and Waltham Historical Society board member. The fee is $10, but admission is free for Historic New England and Waltham Historical Society members. The session on May 15 at 7 p.m is “Understanding Your Old House” and will feature tips on researching a house’s history and how to care for it. “Paint and Maintain Your Old House” is the topic on May 22 at 7 p.m., and “Weatherizing Your Old House” is the subject of the 7 p.m. session on May 29. The last three events of the month will cost $5 for members of Historic New England and the Waltham Historical Society, and $10 for the general public. Registration is required; call 617-994-5959 or visit www.historicnewengland.org. - Megan McKee