Roughness height table:

Surface
Absolute Roughness height ε
(x10-3 m) or (mm)
Copper, Lead, Brass, Aluminum (new)
0.001 – 0.002
PVC and Plastic Pipes
0.0015 – 0.007
Stainless steel, bead blasted
0.001 – 0.006
Stainless steel, turned
0.0004 – 0.006
Stainless steel, electropolished
0.0001 – 0.0008
Steel commercial pipe
0.045 – 0.09
Stretched steel
0.015
Weld steel
0.045
Galvanized steel
0.15
Rusted steel (corrosion)
0.15 – 4
New cast iron
0.25 – 0.8
Worn cast iron
0.8 – 1.5
Rusty cast iron
1.5 – 2.5
Sheet or asphalted cast iron
0.01 – 0.015
Smoothed cement
0.3
Ordinary concrete
0.3 – 1
Coarse concrete
0.3 – 5
Well planed wood
0.18 – 0.9
Ordinary wood
5