I've just had our slate roof replaced. We think it was 1950s.
I was told the roof was 'close to end of life' 10 years ago, and it was fine, with the occasional repair, until last summer when it started to shed slates regularly. That gave me time to save up.
Our house is detached, a simple rectangle in shape, and 20' x 35'. The roof is pitched, with two chimney stacks and decorative ridge tiles.
We had the house scaffolded, the roof stripped back to the rafters, a new roof liner installed, and new battens. A team of one skilled roofer plus one or sometimes two apprentices stripped all the old slates off and sorted the old slates that were in good condition. Then reslated with new slates on the back of the house, the colder east-facing side, and the old slates on the front which is visible from the road.
Reflashed the chimneys with lead, and replaced five damaged ridge tiles. Then took away all the old slates and cleared up.
It took about two weeks and cost £20,000. We're in the home counties. The roofer was recommended by a builder friend. I got the quote in October 2021 and they started in April 22.
The end result is beautiful, and the new roof liner makes the whole upper floor warmer. Reroofing disturbs 70 years of dust, so when you have a new roof, expect extra hoovering for a few weeks afterwards.