Housing, long term sensible choice

[Pleaseaddcaffine]

So I need some advice.
I have one son with my partner. He has 3 children from a previous relationship.
I own my current home outright, bought pre us living together. This is good for me as no living costs. It's 3 bed semi on a main road but in a nice small town/large village. Good schools locally and 1 mile from my parents. Long ish commute for my work but it's a nice area.
Down side is main road at front but back is a cul de sack, so quite ish and the garden is a small. But there is a nice park 150mtrs away at end of road.
Partner complains its small but he cannot afford to contribute to anywhere bigger so it would be me taking risks etc.
I'd like a 'smarter' house somewhere off the main road in the smae village but it would easily be 130k plus more for a 4 bed as hard to come by in this area.
I'm not sure it's worth the financial risks to do this but I also get that I'd having a 'better' asset in terms of a bigger house got selling on in the future or downsizing.
If dp could contribute then I'd be okay, ring fence my contribution and go for a bigger house. But as things stand it would be me taking all the risk.
The current lack of mortgage means I save regularly and can afford holidays etc plus don't worry about expenses (I'm a bit of a worrier and finaically cautious).
Views?

He has a massive cheek. He wants a bigger house but won't contribute. The house will seem bigger less one occupant. Him. C.F. of the week medal goes to.

If he wasn't living with you, he'd have to pay a lot more than £350 in rent alone for even a 1-2 bed Place, let alone a bedroom each for his kids. And even if you bought a 4-bed, someone would need to share, so it doesn't solve everything ... or perhaps he and his ex would like you to buy a 5-bed to suit them?

There is a dining room currently but it's tiny and a tiny kitchen. Unusable really for a family. The kitchen renovation is knocking them together to make a family kitchen, everyone else has on the road and it makes a big difference.
I have a will but he does not. Same as I have life insurance nd a pension and he does not (despite me nagging)

I’d look at converting the garage, after the kitchen, which is not going to be done for months, after the garden which realistically isn’t going to be done until 2022/23

Then convert the garage possibly into a spec that can be changed to office or workroom. Have it for a space to hang out for the children with desk and tv for gaming or watching. They only sleep in the bedrooms but giving them more space to be in daylight will give you more space in the actual house

I agree that if you do anything it would be the garage conversion but I don't agree that he should contribute towards it financially (if he ever could anyway).

I can see him kicking off later if you split, claiming his share etc

Personally, I'd let him pitch in with any work he can do to help out but I'd keep him 100% out of any financing of it.

He couldn't contribute so won't. Soft furnishing etc and decoration maybe but not the build work.
Again thank you to everyone for being understanding about the situation. It's good to get various ideas, the extra games room idea is interesting rater than as a bedroom.
The garage conversion also requires him moving the stuff for his work elsewhere eg hiring a lcokup but the payoff is more room for the family at minimal cost

The garage conversion also requires him moving the stuff for his work elsewhere eg hiring a lcokup but the payoff is more room for the family at minimal cost

and of course you don't need to nag him to move this equipment to a pad lockup as if he doesn't nothing gets changed for the dc

as a games rooms etc its easy to have a sleep over for teens and not worry about to much noise - so an ideal extra, if it ever happens if he gets his gear out.

I have a will but he does not. Same as I have life insurance nd a pension and he does not (despite me nagging)

How old is he? I wouldn't use the term nagging.. you are trying to get him to take responsibility for his future.
I really wouldn't marry this man, you could lose equity and pension from when you started to cohabit. It isn't sensible as it looks like you will always have to be responsible for your child's future housing and financial needs.

A few years older than me, 39.

I know it sounds trite but I didn't realise how important being sensible financially was untill we cohabited. How he is with money concerns me as while I have a sensible pension and investments, it isn't enough to support two people's lifestyle.