A post-tensioned pile anchor foundation and method therefor creates a void or highly compressible region between a drilled or driven pile anchor surrounding a post-tensioned anchor bolt or tendon and the bottom of a foundation cap. The void or compressible region can be formed by compressible spacers or void forming elements placed between the top of the pile anchor and the concrete cap. As the anchor bolt or tendon is post-tensioned against the cap, the void forming element is compressed or crushed, allowing the cap to be pulled downwardly and the pile anchor to be pulled upwardly toward the cap against the resistance of the surrounding soil.