Breathable underlay

[Morganic]

I have just purchased an Isabella Bolon Breathable Groundsheet for my awning. The supplier recommends the use of a breathable underlay. Is this necessary?

 

[ValA.]

In very muddy conditions these breathable groundsheets can get into quite a mess - and I've seen mud and water seeping up through the 'mesh' on various different types. I presume the 'breathable' groundsheet is to prevent this.

 

[JTQ]

I have just purchased an Isabella Bolon Breathable Groundsheet for my awning. The supplier recommends the use of a breathable underlay. Is this necessary?

The breathable ground sheet just like the Bolon will allow mud slurry to seep though if you are in puggling about conditions so I doubt that is the reason; possibly it could be to help alleviate any stone damage on a more aggressive hard standing pitch?
I don’t feel it is strictly necessary but the Bolon is an expensive investment and I at least would put a liner of sorts under the local step 'foot-fall', and step's foot area where the most damage is likely to occur.