We did a major Reno with meridian homes we love them.

Any other suggestion? Not OP but am interested also.

You could start with Design/build firms that start with helping with the design and see the project through to the end stages. There are many in the region. CASE Design is the first that comes to mind but there are many other's. It would at least give you and your parents an idea of scope of project and cost.

My parents are aging and their 1930's Bethesda house is no longer suiting their needs. They need to reconfigure the main floor and put on an additional with a main level master, full bath and laundry. Currently they only have a half bath on the main level and their laundry is in the basement. They want to stay in their house until the end so the only option is a major renovation. Does anyone have a referral for a contractor? I guess they'd need an architect too? I have no idea where to start or how to help them. Thoughts?