Sisters ex wants money for what he put into house.

[howfartospar]

They were married and now soon to be divorced. They lived in a house owned by my parents for which they paid rent. When my sister was pregnant, her ex built and paid for a double extension (costing around 50k)
Now things have ended, he's asking for funds from my dad (he's even sent him a bill from his building company) so that he can put a deposit down on a place.
They have 2 children under 10 which they now co-parent. Things are very raw between them and they are not on great terms. Should my dad / sister pay for the extension, as i can see this matter ending up before the courts.
Any informed advice gratefully received

I think it probably is something that would be covered under the financial decisions as part of the divorce.

Realistically though, he did 50k of work to a house neither him or his wife owned, so I can't imagine he will get anywhere. He may take the father to small claims court after the divorce? Has the father got any communications between them about there being no charge for it?

Yes as the value of the parents house will have increased by more than 50k from the extension.

Your sister and Dad need to pay for an hour or two with a solicitor and get a proper legal opinion on this. Yes it will cost money, but far less if everyone can agree on a reasonable course of action, informed by proper legal advice, rather than fighting it out in court.

I guess how successful he's be is dependant in what the circumstances are?

We're they paying a market rent or a reduced rate of rent? Was the house intended to pass to your DSis at some point? Did your DF agree to the extension? Did your DSis' ex consult them in what he was doing or did he just go ahead and do it without their approval? Who paid the rent?

And most importantly, what, if anything, was agreed in writing (including emails and texts)?

When there's a break up it's important to be as financially fair as possible , especially where kids are involved as you want a reasonable parenting relationship to evolve when the dust settles.
With a rented house I don't know what the position would be legally. In an owned house the assets, including house profit are often shared equally. The work has added to the value of your dad's house and your sister, living there, also has the advantage of the extra space. I would think a fair solution would be for him to receive 50% of what he put in for his own house deposit ...so £25 thousand. No idea if this would stand in law.

Bit late to collect. Rude.

I think you heed legal advice, not mn advice.

Was the work done as a gift?

I think as a rental he’s not entitled to anything. Same as a non married couple and one buys a new kitchen but doesn’t own the property.

That said, with a huge increase in the properties value and him being the father of their grandchildren and needing space to accommodate them when they share custody, and if this can be archived I think sharing the difference 50/50 is something to consider.

I think he probably has a claim but this is complicated and will depend on a number of factors e.g. terms of the tenancy, whether there is a constructive trust, intentions of the parties, whether your sister is entitled to half of this asset if it does materialise. I'm not experienced enough to give you good legal advice on this; you will need a solicitor for this one because there are a lot of facts that will determine the outcome.