A flap-type pressure relief valve includes a frame defining a flow opening therethrough with a flexible flap valve element positioned adjacent the frame (12) to overlie the opening (24) and allow fluid flow in a first direction through the opening (24) while preventing flow in the opposite direction. A retainer assembly for joining a peripheral edge portion of the flap valve element (30) to the frame (12) comprises an elongated retainer bar (32) integrally joined to the frame (12) at one edge and connected to the frame at the other edge along a side of the flow opening in overlying relationship to a peripheral edge of the flap valve element (30). The retainer bar (32) has a retainer surface spaced from the frame a distance slightly greater than the thickness of the flap valve element (30). Retainer pins (40) extend from the frame (12) through openings in the flap valve element (30). The assembly thus supports the flap valve element (30) in a freely floating manner without forming air leakage openings.