At the entrance to my road, numbers 1 & 3 are a pair of 1970s 3-bed semi-detached houses, with 1 being a corner plot with a wraparound garden.

The owner of number 1 has managed to get planning permission to build an addition new property adjoining the existing one, turning them into a 3-property terrace.

As number 3 will now technically be an end terrace instead of a semi-detached, would this change in status have any detrimental effect on the value of their property, and is there any legal recourse for this?

Seems unlikely.

I doubt it’ll make any real difference. There might be a tiny change in value but it’ll be lost in all the noise of other factors that impact on value. Almost certainly no comeback or legal recourse though

I had a friend that claimed she lived in a quad semi. It was a terrace of 4 houses 😂

Number 3 is still semi detached, only attached by one wall.

Bigger impact if the new 1a looks awful. Do what you can to get something attractive built. That might mean it looks different to the others, so they others still look like a semis if you see what I mean.

Number 3 is still semi detached, only attached by one wall.

No. It’s now end of terrace, but still terrace. In all practical senses it’s semi detached but for technical things, like insurance, it’s a terrace.

No.
But you could check their parking arrangements, that the new unit isn’t too big for the plot etc. otherwise it’s just nimby.

had a friend that claimed she lived in a quad semi. It was a terrace of 4 houses

I used to work in an estate agents. The end terrace was referred to as a quasi-semi. But that’s Cheshire for you.

but for technical things, like insurance, it’s a terrace.

Kind of, it’s an end-terrace. I bet there’s a slight difference in rating for an end-terrace over a semi; but I also bet it’s negligible.
It’ll probably be because there’s a potentially higher fire risk in a terrace row (both ways – I mean your’s could burn down due to fires in the other houses, or fire could spread from your’s to the other houses).
Some insurers do have different options when you ask for a quote (semi, end tce, tce etc) so that probably means they use that data. Or it could mean that they never had the data in the past and are now collecting it on new quotes because their systems are better.

No. It’s now end of terrace, but still terrace. In all practical senses it’s semi detached but for technical things, like insurance, it’s a terrace.

Structurally, I assume, the external (gable) loadbearing wall will still exist at the end of #1 only now it will also serve as a party wall between #1 and the new build.

I have no dog in the fight as I’m not connected to the property in question other than living in the same road, I was just idly musing.

The planning permission has already been approved and work has started – Link to application if anyone is that interested..

When I’ve got home insurance it’s said to count end of terrace as semi detached so I assume they’re treated the same

I once had a link semi, a semi connected by my garage to my neighbours living room wall.

was that a terrace?

Who cares?

Ours is an “end terrace” built back in 1810. It is actually half of a row of 4 houses with the end 2 (ours) knocked into 1 back in the 1930s. It was marketed and sold to us as a Semi, but as far as the insurance is concerned it is a terrace, and we get a cheaper premium.

Can’t see it affecting the value as the original end house hasn’t changed and the new one on the other end will obviously be an addition. Probably won’t do the middle one any favours though.

Agents have been advertising end terraces as semis for years, so 3 should be ok

I’d just be more wary of issues that another house might bring to drainage, sewage, etc, as well as the usual parking and other issues.

It seems to be the in thing around here though, about 4 of them on our estate, weirdly one has the new build on a different street, and a high number, so will cheer the postie up!