Company wants me to pay extra for it but why do I need it?
Probably to keep the moisture in the soil and not make the air under there damp. Wise investment if done properly. I sure hope he intends to put the plastic on the ground, right?
Its a vapor barrier, and every REPUTABLE mobile home outfit includes it with every setting, leveling, connecting, and underpinning job. All that should have been settled at closing.... If these highway robbers insist that its extra, stop them, tell them to drop what they are doing and you will get a reputable crew out there....
Moisture, vegetation growth, radon. Many good reasons for it. Make sure it's air/water tight, no rips and the seams are taped with proper sealant tape. The higher mill the better. I think it's at least 6 mill. Pay attention and don't let them cheat you.
Probably because the factory demands it to keep your warranty, or it's code with your building department
