An existing monopole is strengthened to accommodate loading associated with additional elements included in over-the-air communications systems by placing expanding foam and aggregate, light weight aggregate concrete, normal weight aggregate concrete or other types of fill material into the hollow bore in the interior of the monopole. Monopole strengthening may equire base plate strengthening, adding anchor bolts and/or foundation strenghtening. This permits an existing monopole to accommodate more elements than were initially envisioned when the monopole was initially erected.