Smelly Groundsheet.

Probably because it's being folded up whilst still damp/wet. Try soaking with bleach for 24hrs and then a good jetwash. 

Another thread further down with same problem. 

https://www.caravanclub.co.uk/club-together/discussions/information-technical-tips-advice/caravans/smelly-awning-carpet/

Thank you, but already Zoflora and jet washed it. It is now hanging on the line in the rain. Reading the older posts people seem to think it's an animal issue... It can't be. This is our 3rd g groundsheet we have bought because we can't get rid of the smell. If it is due to damp (highly likely and we had put it in airing cupboard to dry completely) then it seems that this type of groundsheet cannot cope with damp grass. Maybe we need to buy the rubber breathable groundsheet. 

Would it be worth putting the rubber pads down first (like a jigsaw) and laying the carpet over the top. 

Zoflora is a disinfectant not a bleach. 

 It is possibly off-gassing. They are made of polymers that will under the right conditions produce gas that smells bad. You can clean as much as you want it wont stop it. Leave it out in the sun to bake, this ages the material but drives out the nasties.  

Also, on grass if it does not breathe very well the grass breaking down is pretty pungent and happens very quickly as soon as it starts to sweat.

Also, the other poster with the same problem has a Kampa carpet, if yours is the same make and type then I would suggest that the maker has  got the polymer chemistry wrong and this is causing the smell.

I am looking for a groundsheet to put outside the door of my motorhome so I can wipe dogs feet and remove my boots before entering. 

was wanting to know what everyone uses. Theres the woven ones that don't encourage worms etc. It's got to be breathable. 

It will be outside in what ever weather with no shelter. 

What do you all suggest.

Aldi. Cheap jigsaw like mats, think they are sold in packs of 8-9, so you can link together to create whatever size you need. We usually carry four for what you describe, just outside MH door. Can be washed off easily. Had ours some six years now, little damage, super lightweight, cheap to buy. Left out, used on grass and gravel.

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They are colourful😁 I think the Aldi ones are either green, blue or black. Good to walk on though. We had to use them for dogs when staying at YRP, horrible pitch surface there, some of clippings are ankle rolling size.