Quoting from Cloughs first edition, published in 1962,
"In 1941, part of the north corner of the building collapsed, rendering the structure unsafe. The high cost of putting the defects in order was considered unjustified, hence the whole great roof was dismantled, the slates and wood beams being sold to a local contractor."
also " the four furnaces were removed in 1926, and the worked stones from them used to build the four cottages which face the road above the CB inn."
There are fully detailed plans of the building and of course more text, this book, for those who have never seen/read it is a great study of long vanished/forgotten smelt mills in the yorkshire dales. A second edition was also published with more photo's.
Still supporting Rampgill. last time I looked