  In this first paper in a series we present a study of the global dust
emission distribution in nearby edge-on spiral galaxies. Our sample consists of
16 angularly large and 13 less spatially resolved galaxies selected from the
DustPedia sample. To explore the dust emission distribution, we exploit the
Herschel photometry in the range 100-500 $\mu$m. We employ S\'ersic and
three-dimensional disc models to fit the observed two-dimensional profiles of
the galaxies. Both approaches give similar results. Our analysis unequivocally
states the case for the presence of extraplanar dust in between 6 to 10 large
galaxies. The results reveal that both the disc scale length and height
increase as a function of wavelength between 100 and 500 $\mu$m. The dust disc
scale height positively correlates with the dust disc scale length, similar to
what is observed for the stellar discs. We also find correlations between the
scale lengths and scale heights in the near- and far-infrared which suggest
that the stellar discs and their dust counterparts are tightly connected.
Furthermore, the intrinsic flattening of the dust disc is inversely
proportional to the maximum rotation velocity and the dust mass of the galaxy:
more massive spiral galaxies host, on average, relatively thinner dust discs.
Also, there is a tendency for the dust-to-stellar scale height ratio to
decrease with the dust mass and rotation velocity. We conclude that low-mass
spiral galaxies host a diffuse, puffed-up dust disc with a thickness similar to
that of the stellar disc.
