Hi Dedo,
The default of surface mapping uses the surface UV in each to define the texture width and height. As violine mentioned, if you use a Planar mapping method for all three using this mapping option in object properties with all three surfaces selected, you can achieve a uniform texture across all.
I would also suggest holding down the shift key when drawing the planar mapping widget. This keeps the aspect square and often matches most textures that have been made tilable.
