Typical neutron spectra as found at high energy electron accelerators outside concrete shielding of various thicknesses (at 90 degrees) have been calculated at three electron energies (100 MeV, 1 and 10 GeV) with the FLUKA Monte Carlo transport code. The results have provided useful information about neutron attenuation lengths and about the fraction of neutrons with energy larger than 20 MeV, not detectable by the usual radiation protection instruments.