A method for forming a metallic structure having multiple layers (824; 1202; 1204), comprising: providing a main tool having a main formation surface that defines a recess corresponding to a desired shape of a first layer of metallic material; depositing the first layer of metallic material on the main formation surface using a cold-spray deposition technique; positioning a secondary tool having a secondary formation surface in a portion of a first volume (810; 1206) defined by a first surface of the first layer of metallic material; depositing a second layer of metallic material on the secondary formation surface and a portion of the first layer of metallic material using the cold-spray deposition technique; removing the secondary tool such that the first volume (810; 1206) is positioned between the first layer of metallic material and the second layer of metallic material; removing the first layer of metallic material from the main tool to expose a second surface of the first layer of metallic material and to separate the metallic structure (824; 1202; 1204) having the first layer of metallic material, the second layer of metallic material, and the first volume (810; 1206) therebetween from the main tool; positioning a tertiary tool having a tertiary formation surface in a portion of a second volume (816; 1207) defined by the second surface of the first layer of metallic material; depositing a third layer of metallic material on the tertiary formation surface and a portion of the second surface of the first layer of metallic material using the cold-spray deposition technique; and removing the tertiary tool from the second volume (816; 1207) to form a first double-wall structure (824; 1202; 1204) such that the second volume (816; 1207) is positioned between the first layer of metallic material and the third layer of metallic material. providing a main tool having a main formation surface that defines a recess corresponding to a desired shape of a first layer of metallic material; depositing the first layer of metallic material on the main formation surface using a cold-spray deposition technique; positioning a secondary tool having a secondary formation surface in a portion of a first volume (810; 1206) defined by a first surface of the first layer of metallic material; depositing a second layer of metallic material on the secondary formation surface and a portion of the first layer of metallic material using the cold-spray deposition technique; removing the secondary tool such that the first volume (810; 1206) is positioned between the first layer of metallic material and the second layer of metallic material; removing the first layer of metallic material from the main tool to expose a second surface of the first layer of metallic material and to separate the metallic structure (824; 1202; 1204) having the first layer of metallic material, the second layer of metallic material, and the first volume (810; 1206) therebetween from the main tool; positioning a tertiary tool having a tertiary formation surface in a portion of a second volume (816; 1207) defined by the second surface of the first layer of metallic material; depositing a third layer of metallic material on the tertiary formation surface and a portion of the second surface of the first layer of metallic material using the cold-spray deposition technique; and removing the tertiary tool from the second volume (816; 1207) to form a first double-wall structure (824; 1202; 1204) such that the second volume (816; 1207) is positioned between the first layer of metallic material and the third layer of metallic material.