HI Ruth,
I thought I posted this reply a couple of days ago but I can't see it here, so off I go again.
I grew up in Llanfaredd, parish neighbouring Llanelwedd. 1/2 a mile from the house in question. I think the house you are taking about is also known as Rock View. The house marked on the map that Mazi has posted is the one I'm calling Rock View. The house is a pair of semi-detached sitting alone on the hillside below the current Llanelwedd Granite Stone Quarry.
When I grew up (1960's) Sid James(he worked in the quarry) & family lived in one of the houses, my mum was a bridesmaid to his daughter when she married in 1947. After Sid, a Mr Jones (quarry manager) lived in one of the houses & his son(Headmaster to Llanelwedd Primary School) lived next door & still lives there. All these people are dead now other than the retired headmaster, who I think owns both houses.
I recently found online a picture of Rock View House, taken sometime in the 1920's by a local Mid-Wales photographer (Percy Benzie Abery 1877-1948), many of his photos are stored in the National Library of Wales in Aberystwyth. You can access the pic' on-line. I put Rock View, Llanelwedd into a search engine (G...le) & it should take you straight to the pic, you can also try National Library of Wales catalogue number: vtls004488737, Notes (acquisition): PBA 13/11.
The house/s looks the same today but with more growth around it & it would mostly be hidden by a roadside hedge from the road when passing.
I don't know anything about the house's history but it is likely to have been owned by one of a local estate owners during the 19thC. In my time, the quarry grounds & this house is built on the quarry hill grounds was owned by the Gwynne-Howell's family, I understand that they did/do? receive a percentage of every ton of stone that leaves the quarry.
Just looked up, Howell Gwynne Howell of Llanelwedd Hall was the High Sherriff of Radnorshire in 1858. Llanelwedd Hall isn't there now but it was where the current Royal Welsh Agricultural Show takes place every July. The quarry wasn't behind Rock View in 1840's, I don't know the date it started but when it did it was to the right (right as in looking at house) of the house, between Rock View & Gellicadwgan Farm. By the 1960's the first quarry area wasn't worked & filled in with water. I understand that my grandfather's job had been to go to work early to pump out the water so quarrying could take place for the day.
Up to 1960's when the local railway line was closed, the quarry was behind Rock View & the stone was sent on elevated belts across the road to below Rock View to be transported by rail. It must have been a very dusty place to live for Sid James family. That's enough babbling!
Any questions?
Ithon