Sub-floor options

[Necrobus]

Hi Everyone, I just purchased a 87 Thomas flat nose style bus and just finished removing the old vinyl/wood flooring. My question is this. Has anyone considered using polyethylene sheets as a sub floor for their bus. I know its not cheap, but Ive found 4' by 8' sheets at 1/2 thick (like a cutting board) supposedly at half the weight of plywood or osb and twice the psi strength. I figure also It may give me a bit more headroom. Any thoughts.....

[eggman]

My thoughts on polyethylene is: how well will it hold a screw? Will any kind of floor covering stick to it without sliding? What are the insulating properties of it versus plywood?

Lets look at weight. Polyethylene is about half of plywood (your info). Lets figure 25 pounds for the poly sheets and 50 for plywood. I used 8 sheets of plywood for my floor. If I would have used polyethylene, I would have save approximately 200 pounds. This is in a vehicle that is rated for 30K pounds, currently weighs about 17K pounds.

Now lets look at cost. Low Density Poly-E 48" x 96" 1/2" Thick is $261 per sheet. 1/2" plywood is $17.50 per sheet. Figuring 8 sheets: poly sheets would cost $1,880 (after quantity discount at usplastic.com plus shipping) and plywood would cost $140 (Lowes, plus taxes). Now, you may be able to get it cheaper than the $261 per sheet, I dont know. But I believe the insulating properties of plywood far outweigh those of the poly sheets. Not to mention, the price difference could mean a nice shiney new generator for the bus.

$1700 more or less is a huge amount of money to save 200 pounds.

Just my $0.02

[Necrobus]

Too true on the cost eggman, one of the reasons I first thought about using polyethylene sheets was after I removed rotted out plywood. Polyethylene by its nature doesn't give mold a feeding ground so to speak, and in the northwest, that is a plus. As far as insulating properties, I suspect that it would be an excellent thermal barrier to the steel floor ( I would still likely use half inch rigid insulation between the two). Some web sites that I've visited claim that polyethylene is as workable as wood and as far as using screws I would likely pre- drill anyways and use machine screws. As far as weight is concerned, 200 lbs isn't much unless one considers that throughout the entire construction, this could mean thousands of pounds difference. Im no math wiz but Im pretty sure that equates to better fuel efficiency.

At any rate, may not be a viable solution, and it is expensive, but I would'nt discount the idea so quickly.

[eggman]

I do understand about the "wet" issues in the northwest. However, if you are planning on using polyethylene sheets through out the entire process, I would think that they would be awefully hard to paint. I know how much wood I have used so far in my conversion, and to multiply the cost of it versus the sheeting by 12 to 13 times. WOW, that is an expensive bus conversion. Now, not saying that it wouldnt have special uses inside the bus. Like around the shower, sink, toilet areas. Or anywhere else it would be wet, polyethylene would be a good choice.

From what I know about polyethylene, is that it is used in the tubing for radiant floor/ceiling installations because of its ability to give off heat. If you are wanting something to insulate you from the cold coming from the floor, I would (did) 30# roofing paper for moisture barrier, 1" think blue polystyrene board, covered with 3/4" tongue and groove plywood.. Otherwise I think you will be cold with polyethylene as a part of your floor.

HTH,