Despite it's large size my rats needed no help to figure it out and did it far sooner than I expected. My current maze uses 11cm and my next maze will likely use 13 cm for its square unit. I do however recommend a heigth of 15 cm for each passage. Finally I built my current maze as a 8 x 12 rectangle but this allows for only one rotation. Making the maze itself a square allow for two more rotations to help defeat the using of scent to find their way through.
Acrylic is expensive and little tricky to work with, but durable and easy to clean.
Wood is cheaper but more dificult to clean well, but this can be compensated for by using a liner of butcher paper. Prepare the floor first, Then draw the square grid on the floor and drill a hole at each intersection The hole will be used for screwing down the post. The post is made by taking a 2 X 2 and making a slot in each of it 4 sides. I'd recommend using a table saw for this part. Finally drill a pilot hole into the bottom of each post and then screw it to the floor of the maze.