nate
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Post by nate on Dec 14, 2017 13:01:46 GMT -8
About to replace the entire plywood floor with fiber board on my '63 comet. I'm wondering if the fiber board needs to be protected at all underneath? Here's a picture of how it is sandwiched in with a sill board. C60C6054-1FC5-4A46-AEA9-C3871BDF58F7 by nate kastle, on Flickr I was thinking of replacing these two 1x4s with a 2x4 all the way around and then adding wood supports to keep the fiber board in place. The side wall and framing would are nailed to these two pieces. Has anyone added rigid insulation underneath the fiber board at all or otherwise improved on this floor system? I can't take any more interior head room so insulating on top of the plywood isn't an option. The original floor was 5/8" plywood on top of 3/8" fiber board. My local Menards only carries 1/2" fiber board for about $10 for a 4x8 sheet.
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Post by vikx on Dec 14, 2017 23:17:33 GMT -8
Well, you could clean/repair all undercarriage then use spray foam. (not rattle cans, pro applied) I never recommend foam for the rest of the trailer, but it might be good underneath. Of course you would have a huge job masking what didn't need to be sprayed... and trimming wouldn't be fun. I'm not sure if it can be undercoated with a product to protect from road debris and damage?
Just a thought but needs a LOT of research. I've never done it.
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nccamper
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Post by nccamper on Dec 15, 2017 6:51:56 GMT -8
"Has anyone added rigid insulation underneath the fiber board at all or otherwise improved on this floor system?"
I never had a problem with water damage up through the foam board. It's always water seeping down the walls that's trouble. In your photo it's the outside wood that rotted.
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mobiltec
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Post by mobiltec on Dec 15, 2017 15:07:17 GMT -8
What do you mean by "fiber board" You should use Exterior Grade CDX or ACX. "Fiber Board" is not good with moisture. It will just turn to mush when it get's moist. If it gets wet you could step right through it and maybe brake an ankle. Plywood is your best bet.
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Post by Deleted on Dec 15, 2017 15:31:52 GMT -8
Nate - Did you intend for the fiber board (Bildrite up here in Minnesota) to be used on the surface that your vinyl or finish floor will sit on top of? Or did you intend it to be the barrier on the bottom side facing the street? As Mobiltec mentioned, fiberboard is very soft and intended for exterior wall sheathing in homes, not sub flooring for anything.
If used on the bottom side of your floor structure, just coat it with an exterior water repellent product. Folks on the forum often use fence post paint. I believe Vikx can give you info on the exact stuff she uses. Then sandwich foam insulation in between for a great insulator.
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mobiltec
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Post by mobiltec on Dec 15, 2017 16:38:09 GMT -8
The stuff is REALLY heavy too.
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nate
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Post by nate on Dec 15, 2017 17:16:57 GMT -8
Oops, I meant to say that I was replacing the plywood floor AND the fiber board (or whatever it's called) that sat underneath. It looks very similar to this stuff that Menards calls "insulated sheathing," among other things. Am I wrong? I initially wondered if that fiber board needed to be sealed (thanks bw), or even if I could add rigid foam insulation underneath the plywood instead (or in addition to the fiber board). This would have the plywood floor sitting directly on top of the trailer framing, which is not original. The original fiber board sat on top of the floor joists and outriggers between the plywood. It stayed remarkably intact and didn't appear to be coated with anything. Most of the floor was in great shape, too. I do plan to pick up that fence post paint that vikx uses for the sill boards. I can slather that on the fiber board as well but I read on a post that the fiber board needs to breathe and it will dry out if it gets wet. I'm just trying to make sure I don't have to revisit the floor again anytime soon. IMG_0848 by nate kastle, on Flickr
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Post by vikx on Dec 15, 2017 21:58:33 GMT -8
Nate, that is similar to the old Celotex or today's sound board and yes, it is fiberous material. If you will be going down to the frame you can use a better material. I've recently used 1/8 masonite coated on one side (rough side down). I had good luck with it, it protects the belly insulation and doesn't collapse when the bolts are tightened. If you won't be going down to the frame, the belly is very difficult to patch or replace because it goes on before the sills and joists. I'm guessing you are going to do a frame up. Here is my Cardinal build: s189.photobucket.com/user/vikxphotos/library/58%20Cardinal%20Two%20into%20One?sort=6&page=18&hotlinkfix=1513403524708That is page 18 where I began the belly. Scroll backwards to 17, then 16, etc. Henry's Damp Proofer is no longer sold at Home Depot, so I switched to Black Fence Paint from Tractor Supply. All you need is something thick to coat the underbelly, even white roof coatings will work. LOL.
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Ten
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Post by Ten on Dec 16, 2017 6:31:38 GMT -8
Henry's Damp Proofer is no longer sold at Home Depot, so I switched to Black Fence Paint from Tractor Supply. All you need is something thick to coat the underbelly, even white roof coatings will work. LOL. ...Probably better underneath than on top!
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nate
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Post by nate on Dec 16, 2017 6:59:51 GMT -8
If you will be going down to the frame you can use a better material. I've recently used 1/8 masonite coated on one side (rough side down). I had good luck with it, it protects the belly insulation and doesn't collapse when the bolts are tightened. Thanks vikx. Wow, that's a lot of projects! I am down to the frame already. I'm currently working on the trailer frame, getting it repaired and then painted with Por 15. I like your suggestion to use sealed masonite. That sounds better than the fiber board for sure. My trailer's original setup was 3/8" fiber board and 5/8" plywood equalling 1" of material. Do you think it would be okay to use 1/4" masonite, then 1/4" foam insulation, and then 5/8" plywood? I don't really want to build up too much into the trailer, which I assume happens when you build a frame for the floor. I was not planning on doing that. Would it be wise to re-think that?
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Post by vikx on Dec 16, 2017 21:37:46 GMT -8
The Cardinal had an insulated floor "cavity", so the foam was inserted between joists and cross pieces.
The way your trailer was built sounds like an uninsulated floor with ply on top of it? The foam will have to be inserted; don't build on top of it or your bolts will loosen as it collapses.
You really don't need a belly for an non insulated floor. Many times, manufacturers used tar paper under the ply.
You might consider installing the floor with insulation underneath as mentioned above.
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Post by Teachndad on Dec 28, 2017 8:32:31 GMT -8
Hi Friends, I was researching how to replace the floor on my Westerner and this link might be helpful. It's one of Larry's videos. www.youtube.com/watch?v=sG_24jEt47E It doesn't cover the fiber board, though. Cheers, Rod
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mobiltec
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Post by mobiltec on Dec 28, 2017 11:22:22 GMT -8
Hi Friends, I was researching how to replace the floor on my Westerner and this link might be helpful. It's one of Larry's videos. www.youtube.com/watch?v=sG_24jEt47E It doesn't cover the fiber board, though. Cheers, Rod I would never use fiber board for the floor. Plywood only.
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Post by alfadriver on Oct 28, 2020 14:47:04 GMT -8
Hi Friends, I was researching how to replace the floor on my Westerner and this link might be helpful. It's one of Larry's videos. www.youtube.com/watch?v=sG_24jEt47E It doesn't cover the fiber board, though. Cheers, Rod I would never use fiber board for the floor. Plywood only. Bringing back a very old thread, but it does address the question I have here in 2020. I have some rotten floor in the rear corners of my Wheel Camper, and when I pulled up the plywood sheet, there was a fiber board insulation. I should measure the original thickness of the plywood... But it sounds like it's not recommended to put the fiber board back in the floor- instead replace it with a masonite board. Is that still the recommendation? The sub floor board looks exactly the same as the board shown at Menards (I think that was). Thanks for the info- this happens to be my first post here.
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Post by vikx on Oct 28, 2020 19:28:35 GMT -8
Sound board (fiber board/Celotex) was used for the belly years ago. It was coated on the underside and laid on the metal frame, then the joists went on top. Most trailers using Celotex had floor cavities with insulation, then a plywood floor on the top.
Some of my trailers had plywood over roofing felt, others plywood coated on the under side. The trailers like this did not have an insulated floor.
If you are patching the floor, it is very difficult to piece the Celotex. If you want to insulate, you will have to figure out a way to hold the insulation in place. Perhaps some framing and plywood belly pieces?
If you are doing the entire floor, it is recommended that you use some sort of belly material, insulate between joists and cross boards and use plywood flooring. I like foam board insulation because it won't absorb moisture.
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