This work. presents a methodology to exclude backfolding (overlapping of sequential segments) in lattice models for freely jointed linear and branched polymer molecules. The introduction of conditional weighting factors that account for occupancy of sites by neighboring segments leads to the generation of new recursive relationships to compute the chain weighting factors that; quantify configurational probabilities. Calculations are performed for representative linear and branched homopolymers and copolymers. The results indicate that the allowance or prohibition of backfolding has a significant effect on the predicted structure of adsorbed polymer layers, especially the surface volume fractions and adsorbed amounts, at least when the segmental adsorption energy is relatively low.