Granny annexe

They may deem*

Apart from all the things already mentioned, you will need to factor in the services to the building. Assuming you get PP laying new services to a building is extremely costly, the garden will need to be dug up to lay pipes for clean water and sewage pipes. There are strict rules applying to this work and often can only be undertaken by the water providers. They deem a septic tank is needed.
To bring electricity to the building is easier, but once again costly. It might help to enquire at your local planning office about the building regulations for such a project.

All the 'what iffs' that others have offered up are exactly why you need legal advice before you proceed any further with your plans.
The proposal might be the perfect solution for you all but life has a habit of throwing all manner of obstacles at us.
Do talk to a solicitor.

Have you read a thread on here very recently from a gran who moved into a granny flat with her son and ended up owning nothing and being unhappy but tied into an abusive relationship with all her money and assets gone
She never thought it could happen

I wonder how she is did the thread finish ?

You may of course be extremely wealthy with acres of land, no neighbours and can have a lovely designer home built with separate access.

But maybe not and your "home" a glorified shed. Take legal advice.

As your house won't be yours anymore, and heaven help you if you are suddenly estranged as so many GNs seem to be, why not sell up and downsize and help them out with some money to buy what they need.
Also ďivorce is always a possibility however much it may not seem likely.
As said above planning permission could take forever.

Compromising, those gremlins.

Potentially if the marriage fails, you could be homeless, it would be no from me. Stay independant. Buy a smaller place and get sorted, then see what you can give them without comoromising your living standards. Once a duty you become a burden.

We didn't do this exactly but moved to daughters flat and they had our house then the relationship broke up and we all live back here.
I found it difficult seeing what they did to our house. Even silly things like replacing the shower curtain with a plastic screen.
On the whole the DGC have flourished but you have to be very adaptable and resilient.
And yes take legal advice.
And don't help you'r children too much it can backfire.

Each to their own but for me personally it’s a big no no
I know for some it seems to work wonderfully but I just think it’s unfair on the young people to (as they get older) have a ‘care home’ in the garden
I m sure for some families its a wonderfully practical experience and I envy them but for me personally I think it has so many possibly red flags both practically, legally and lovingly
I know someone who is very, very successfully co living with family 😀 so it can be done
I wish you well though

Don't do it. Over my years on GN I have read to many horror stories of parents doing something like this only to end up as unpaid permanent babysitters. Children's marriage break ups which have left the parents homeless.

Also have you got planning permission to build in the garden ? I doubt very much you will get it . Also will there be a separate access and drive for you. Have you discussed this with your neighbours? I doubt very much they will let the build go ahead.

If your daughter can't afford a home of her own then she needs to save more.

And yes I expect to get rude replies but there are things you haven't taken into consideration. Planning permission can take months to go through. My daughter and son in law had to have planning permission to change the loft room into a bedroom and have every door in the house changed to fire proof . There was no exterior build it was all internal.

As Birthto110 please take legal advice if you haven't already. Is daughter married? If so the consequences of divorce should be taken into account.
Omar are a major manufacturer and have a wealth of information on their website
www.omar.co.uk/buying-guide/buying-for-your-own-land/
Their buildings conform to all necessary standards and I've known many folk that have loved living in them.
They are very easily erected once on site and maintenance is low. How exciting - good luck.

Don't have experience no - but are you aware that if it's sold/bought at a discount the difference between market value and the discounted value might be deemed 'a gift'? Therefore potentially taxable - (but exempt if they live for another 7 years I think - worth checking properly) . Also would anyone know if it's deemed a 'gift with reservation' because parents continue to live on the property?