Kaiya Hiya

Hi Terry, thank you! yes for visual purposes similar to an RV. O.k. that's good to know on the plywood. The manufacturer is Huber. It's a specifically made moisture resistant osb. I would have gone for dryly by GP but their products are basically extinct to the typical residential builder, building a small space. So, that was the best I could do. That's really interesting that your natural home designs are in great condition without any vapor barrier or house wrap. I'd love to build a hobbit type earth home. That will be the next project. If I could incorporate those principles it would be great. I'm not sure how applicable they would be though to what I'm able to do in this type scenario, because it will need to move? I'm all ears though. I guess I was opting for the vapor barrier because it will be a small space and I thought it would make it air tight as well as help control moisture? Although, with that said, there would really be no use for it in the floor??? I'm not so sure. So, I'm still wondering do I put my tar paper in the floor for moisture control to help prevent the floor joists from rotting from moisture build up? The joists are wood 2x6. I would really like for this structure to last as long as I possibly can so it's not another generations problem, so I'm trying to think through this well. I think what is sounds like the consensus is no vapor barrier and yes to the tar paper??? Would Input something else in place of the vapor barrier under the subfloor? And no, I am not any type of engineer so all those kinds of running tests are not something I would really do... Although the WUFI sounds like it would be useful and interesting. I don't know how to have access to it? Many thanks!
John, I'm not so sure a moisture barrier would be the best on the interior of the osb. It may have ben a good use though had I painted it and then wrapped it in house wrap so the house wrap is the bottom most layer. It's too late for me to do that but maybe it will help someone else. It's a good idea.

O.k. sorry found the radon blankets, reading up now.

I feel like I need to catch up. I'm not an "experienced" builder. How could I access this WUFI? I'd like to stay as organic as possible. I was not happy about using the marine grade paint but mores just looked at it as something I had to do. There will be roux insulation. It could very well end up in northern midwest climates. I am not familiar with the radon blanket material... I just did a quick search and it brought up horse blankets? Were you suggesting the radon blanket go above the floor cavity under the interior subfloor? I'm not sure that radon will be an issue as it's ventilated under the trailer and there is no basement, but if it is a decent vapor/air barrier... it may be an option. Is it a blanket in the sense that it insulates as well?

By the way, I really like the idea of laying some plastic over the soil/ground underneath. I think that will be helpful. Any ideas as to what type of plastic it should be?

Thank you I greatly appreciate all the input. Although, I haven't seen it been used I think the moisture resistant sob double coated in marine grade poly should prove to be pretty resistant. I should also expand that I'm working on a trailer as my foundation. Many people use sheets of aluminum or galvanized aluminum however I chose against that. Laying just taped 1/16 of an inch aluminum under my insulation did not sit well with me as durable or good protection. My bottom layer needs to have some r value which is why I chose the marine grade poly osb but also wick moisture. It will be ventilated below the trailer but not really in the floor cavity because it sits about 15-18" above the ground however when it's moving there is a lot of water, pressure, rocks etc hitting it (another reason why I chose against the aluminum, and that tape never really stays, galvanized would eventually also corrode the trailer). Since it will be a small space and susceptible to condensation due to temperature changes there are small protected outlets for moisture to be gravity fed down and out. The seams of the osb lay over crossmembers on the trailer to keep moisture from getting up into the trailer but allows for it to find it's way out. I want it to be as moisture resistant as I can. Unfortunately changing the sob is no longer an option, and I like it so far... but I know back in the day tar paper has been used for moisture control (just overlapping it a few inches on the bottom layer, not sealed) and thought that would be useful in this scenario but I'm afraid if I use the vapor barrier on the interior and the moisture barrier that it will backfire and trap moisture between the two. I've heard a moisture barrier and a vapor barrier are good, but both can cause joist rot which is what I'd like to avoid... Any ideas?

Hello, My subfloor sandwich plan looks something like this from the bottom up (the bottom layer will take the most moisture), moisture resistant 1/2" osb coated in marine grade poly, floor joists and insulation (roxul) followed by vapor barrier and 3/4" subfloor. My thoughts are to throw in tar paper with overlapping layer simply played over the 1/2" osb on my bottom most layer for moisture control. I don't want it to be so completely sealed that moisture cannot find it's way out, nor do I want to create a scenario where condensation moisture is trapped in and cause rotting of my floor joists. Is it possible to use a moisture barrier and vapor barrier within the same cavity on each side of the insulation? I am anxiously awaiting your wisdom. Thanks so much!