An apparatus for clamping a floor including truss top cords having tongue configured ends and including an overlying sheath having a plurality of bolt receiving apertures, the apparatus incorporating a concrete foundation wall having an upper end forming an outer flange and an inner recess; outer threaded bolts anchored within and extending upwardly from the outer flange and positioned for, upon receipts of the truss's tongue configured ends within the inner recess, extension through the sheath's bolt receiving apertures; and an outer plurality of threaded nuts fitted for engagements with the outer plurality of threaded bolts, the nuts, upon the tongue configured end receipts, upon the bolt extensions, and upon the threaded engagements, clamping the sheath against the outer flange and capturing the tongue configured ends within the inner recess.