Triangular Gatzouras–Lalley-type planar carpets with overlaps

We construct a family of planar self-affine carpets with overlaps using lower triangular matrices in a way that generalizes the original Gatzouras–Lalley carpets (Gatzouras and Lalley 1992 Indiana Univ. Math. J. 41 533–68) defined by diagonal matrices. Assuming the rectangular open set condition, Barański (2008 Discrete Continuous Dyn. Syst. A 21 1015–23) proved for this construction that for typical parameters, which can be explicitly checked, the inequalities between the Hausdorff, box and affinity dimension of the attractor are strict. We generalize this result to overlapping constructions, where we allow complete columns to be shifted along the horizontal axis (as in Fraser and Shmerkin (2016 Ergod. Theor. Dyn. Syst. 36 2463–81) and Pardo-Simón (2019 Ergod. Theor. Dyn. Syst. pp 733–63) or allow parallelograms to overlap within a column in a transversal way. Our main result is to show sufficient conditions under which these overlaps do not cause a drop of the dimension of the attractor. Several examples are provided to illustrate the results, including a self-affine smiley, a family of self-affine continuous curves, examples with overlaps and an application of our results to some three-dimensional systems.