A patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient's airways including at least entrance of a patient's nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient's respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing; said patient interface comprising: a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and a seal-forming structure (16200-1, 16200-2) having a textile membrane (16230-1, 16230-2) constructed and arranged to form a pressure-assisted seal with a region of the patient's face surrounding an entrance to the patient's airways, said textile membrane having a hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure (16200-1, 16200-2) constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient's respiratory cycle in use, wherein the seal-forming structure (16200-1, 16200-2) includes a flexible support structure attached to and supporting the textile membrane (16230-1, 16230-2), the flexible support structure comprising silicone, the flexible support structure and the textile membrane (16230-1, 16230-2) forming a lap joint where an edge portion of the textile membrane (16230-1, 16230-2) overlaps with an edge portion of the support structure in an overlap area, and wherein the textile membrane (16230-1, 16230-2) comprises a textile material and an air impermeable layer applied to the textile material to provide air impermeability to the textile material, the air impermeable layer having a first thickness at a first location on the textile membrane (16230-1, 16230-2) and a second thickness at a second location on the textile membrane (16230-1, 16230-2) that is different than the first thickness, wherein the varying thickness of the air impermeable layer across the textile membrane is outside the overlap area of the lap joint. a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; and a seal-forming structure (16200-1, 16200-2) having a textile membrane (16230-1, 16230-2) constructed and arranged to form a pressure-assisted seal with a region of the patient's face surrounding an entrance to the patient's airways, said textile membrane having a hole formed therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure (16200-1, 16200-2) constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient's respiratory cycle in use, wherein the seal-forming structure (16200-1, 16200-2) includes a flexible support structure attached to and supporting the textile membrane (16230-1, 16230-2), the flexible support structure comprising silicone, the flexible support structure and the textile membrane (16230-1, 16230-2) forming a lap joint where an edge portion of the textile membrane (16230-1, 16230-2) overlaps with an edge portion of the support structure in an overlap area, and wherein the textile membrane (16230-1, 16230-2) comprises a textile material and an air impermeable layer applied to the textile material to provide air impermeability to the textile material, the air impermeable layer having a first thickness at a first location on the textile membrane (16230-1, 16230-2) and a second thickness at a second location on the textile membrane (16230-1, 16230-2) that is different than the first thickness, wherein the varying thickness of the air impermeable layer across the textile membrane is outside the overlap area of the lap joint.