A flush or header beam is a structural member positioned at the same level as the joists and uses joist hangers for attachment just as you would at the ledger board. Flush beams are commonly used for framing angled deck forms such as octagons or on stair landings where a cantilevered beam would be less practical.
This technique can make your deck surface extremely level and increase the stiffness of rails. Low decks also may require a flush beam application to provide ventilation and ground clearance.
Screened porch frames must use flush beams in order to transfer roof loads effectively to the footings placed at the edges of the deck. Overall flush beams perform below the standard of cantilevered beam construction because a composition of hangers and fasteners are less reliable than the positive connection of wood directly supported by wood. Also applying joist hangers is more expensive and time consuming than installing a cantilever or drop beam.
How to build a deck 3 - Framing