Complex sentence: Old Horwood was a building of two storeys and an attic, with walls of timber and brick of late sixteenth century construction, extended in the later seventeenth century, and enlarged in the nineteenth century.
Split into simpler sentences: Old Horwood was a building of late sixteenth-century construction, consisting of two storeys and an attic, with walls of timber and brick. It was extended in the later seventeenth century, and enlarged in the nineteenth century.