Hi Dave,
The Maidum pyramid had three stages of construction - the last stage was the filling in of the 'steps' of an underlying eight-stepped structure so forming a true plane-sided pyramid.
"........in the Middle Ages it consisted of five massive steps superimposed to one another of nearly equal height (Makrizi).......The present state of degradation is due to the fact that the pyramid served as a stone quarry, particularly in recent centuries. From the information given by Petrie, Borchardt, Rowe and other excavators, confirmed by direct examination of the masonry and the descending corridor, it seems certain that the pyramid initially consisted of seven steps formed by an inner core and six layers of masonry diminishing in height from the centre outwards. Subsequently this building was enlarged by the addition of blocks of masonry erected on said steps and by the construction of a seventh layer, so as to completely cover the original monument. The pyramid thus probably comprised eight steps." (M&R Part III, 1964: 10)
It's been suggested that Huni, who apparently reigned for 24 years, began this pyramid with the first two stages, but for some reason, it was taken over by Snefru, and enlarged and completed in stage three as a true plane-sided pyramid - its fairly certain that Snefru was the final owner of the pyramid.
CT