Structural windowsill assembly

A windowsill assembly, comprising:

• An elongated beam member including a first leg and a second leg, the first leg meeting the second leg at a joining region at proximal ends of the first leg and the second leg so that the first leg and the second leg are substantially perpendicular, at least one of a distal end of the first leg and a distal end of the second leg forming a slot, the second leg having at least one beam opening structurally configured to receive a fastener therethrough for attachment to a wall, with an outer surface of the first leg being structurally configured for receipt of a window thereon;
• and
• an insert bracket, including a first portion and a second portion that are substantially perpendicular to each other to substantially match an angle between the first leg and the second leg of the beam member, the insert bracket slidably positionable to overlie a portion of an inner surface of each of the first leg and the second leg, and so as to slidably fit within the slot, the second portion having at least one insert opening corresponding to the at least one beam opening, such that the fastener can be directed through the at least one insert opening and the at least one beam opening to couple the insert bracket and the beam member to the wall.