Period Oak Beam Window Sill Boards, come in kiln and seasoned air dried, the thicknesses we generally use are a finished size of 20-22mm thick and 45-50mm thick.We supply Oak Beams etc. Whether it be a straightforward beam|a beam with corbels or a lintel or facia board for a doorway or window|we can tailor a Oak Mantel to meet your requirements.We also manufacture dried oak beams, oak joists, oak roof trusses, oak boards, oak posts and oak flooring.