In this paper we propose a method to maintain a multiresolution surface codificiation of a fitted surface in the nodes of an octree. The proposed codification is based on the number and the topology of the planes that define the surface of each intersected node. The surface is codified in the maximal division nodes of the octree, then a merging process is applied to detect and merge coplanar facets. At the end of this merging process the surface is encoded in a set of terminal nodes distributed at different levels of the octree. No error is introduced by the decimation method. The algorithm to reconstruct the surface of each intersected node is also presented. Various examples demonstrate that in the best situation a reduction of almost a 50 per cent on the number of polygons can be achieved.