Forest Garden Xtend+ 13×11 Pent Tongue & groove Cabin.Create a place for work or play with this Xtend+ 4 cabin from Forest garden. Easily make this cabin into your home office with a Tongue & Groove timber for a contemporary look and feel that will suit any style of garden. Not only is it easy to construct with pre-cut modular Structural Insulated Panels (SIPs) they’re also as energy efficient as a new build home thanks to the double-glazed windows and insulation in the walls roof and floor.