How do I break the news to dad?

Agree with all. They need to be together. Even though Mom may not physically require NH care - the dementia puts her mentally into needing NH. Also, most ALF will not keep someone with dementia (unable to be on their own) anyway. So even if she is not to that level yet, it will come to having them say "they can't provide level of care she needs" either. Why not move them both now. Even though it may not matter to her - if she was cognizant I'm pretty sure she would want to be with your Dad. He wants to be with her. Basically they are all they have. Some NH with semi-private rooms might even put them in same room. If she has to be in Dementia care unit, might even consider putting your Dad there due to his physical incapabilities if he can handle being in a secured area.
An online search (Medicare.gov, A Place for Mom, and referrals on this website) is a good way to start. Best wishes -

Has your mum's doctor or some other professional recommended that she not be moved? I understand that moving someone with dementia may pose some problems, but I think it would be worth looking into for several reasons which are mentioned above.Your mum may change and be more interested in being near your dad, couples who have been together as long as your parents have, tend to do better if they are kept together, your dad surely would benefit from having his wife near, and it should be easier for you to visit them if both parents are in the same facility, even in separate wings.
I am sorry that your dad has so many health problems. This is a difficult situation. Let us know how it goes.
((((((((((hugs)))))) Joan

I, too, would go with what's good for Dad at this point. Also, call around to the communities near you. Some may be willing to 'go the extra mile' to keep them together, if you think that would be good for your Dad.

wouldnt it also be easier on you if they were in the same building?

If it were me, I would do all I could to keep them as close together as possible. I'm not an expert, but I do know of couples who were in their position and those who were kept close to one another did much better then those who were separated.

Lots of times when a person has dementia/alz they don't know WHAT they want. And what they want could suddenly change, then the person wants something totally different. So I agree in getting both mom and dad together in a facility that can deal with BOTH of them. Probably in different wings of a building, but at least under the same roof so that dad can go see her if he wants.

Your Dad is evidently aware of your mother's dementia, and wants to be with her 'till death do us part' regardless. Since Mom is no longer truly able to make decisions about where to live, I think I would cast my vote with Dad's wants/needs. He is probably very scared, he does not want to lose his wife as well as his former home. It may do his health good to be near her, which is a positive in my book. I think Mom should be moved so Dad can spend what remaining time they have together.

Jeanne - thanks for your comments. Mom has vascular dementia and has little desire to be with dad. He, on the other hand, misses her and wants to be back with her - they've been married for over 50 years

I'm so sorry that your dad cannot go back to ALF.

Why isn't it a good idea for Mom to move to be near Dad? Changing environments will be hard, but missing your Dad must be hard, too. Or doesn't she notice?