Redoing a horrible "unofficial" loft conversion

[DespairingInLondon]

We've seen a house we like and is in our budget but the loft was done up "unofficially" and has a really unusable layout and I think they put the stairs in the wrong place. I imagine we'd need to start over. Is fixing something like this worse and more costly than doing a conversion from scratch?

Would we run into trouble getting planning permission?

What else should we be thinking about? We're FTB, so this is all new to us.

The property is in a highly sought-after area, so I think there's little chance of negotiating much on the price.

Any idea how much a project like this might cost (redoing the layout, adding a loft bathroom. etc)?

Thank you!

I'd be pointing this out and offering less. Why should you pay to fix someone else's shitty mistake?

What sort of house is it? I lived in a Victorian two up two down with a proper loft conversation and it was a great space addition. For some reason I was chatting to a builder about the loft conversation and was told I wouldn't get planning for it now as the refs have changed, something about due to the amount of insulation they have to have means there wouldn't be enough head height unless you dropped the floor to compensate. So you might be able to get retrospective planning but it would have to be rebuilt to modern regs and you might run into the same head height issue. Sorry not really a helpful reply.

I'd say it's probably a 1960s semi-detached. The neighbouring houses with the same floorplan have the lofts done up properly, so that shouldn't be a problem.

It's an area with huge demand and very short supply, and the seller is likely to find someone willing to take it as-is. If we want to stay in this area, we'd just have to deal with it. Question is whether we can do the work needed on top of the high selling price.

The key will be compliance with building regulations. Talking to an architect or specialist loft company might be useful but yes it could cost more...just depends

On a practical level, I have this in my house (we don't use it as a bedroom but it is a great extra space for teenager). When getting quotes for a proper conversion, we were quoted extra as they basically would have to remove the current setup and start again. IIRC it was about an extra 5K but that was some years ago.

In terms of the sale, I am assuming the price is based on the proper bedrooms only? An unregulated loft conversion can't be included as a bedroom (or anything else) for sale purposes, so not sure if renogitiation is an option, as it is essentially an extra?

Planning is unlikely to be a problem as most loft conversions come under permitted development however building regs are another matter and will apply.
Two different pieces of legislation.
Building regs has got more stringent with regards to insulation and energy efficiency and will go up again from the end of this month but the main issue is usually proving that it is structurally safe. Engineers do not like to sign off other peoples work (insurance risks) and you will need to provide evidence that the structure has been calculated and safe.
You will also need to ensure that the rest of the house complied with the fire requirements no that it has a '3rd storey'
It's not necessarily an issue but there is lots to consider. Projects like this I tell clients to treat it like we are starting from scratch.