In 1906 he built a home near Pitlochry to house his library. Forbes' family had frequently holidayed in Pitlochry and his father had befriended the Butters – the area's main landowners – who initially leased and eventually sold Forbes the land on which his house stood. This house, which he called "The Shed" was a large wooden structure with an observatory on the upper storey. It overlooks the valley that in the 1950s would be flooded to create Loch Faskally and the hydroelectric scheme Forbes had proposed in the early 1900s. In Pitlochry he returned to an earlier interest, from 1906 to 1930 delivering the David Elder lectures on Astronomy at the Royal Technical College in Glasgow.