Best Subfloor Consensus?

[Belegedhel]

When I bought my '73, I discovered rotten plywood in all the usual places, which eventually inspired me to do a shell-off and replace the entire floor. When I took everything apart, I discovered that the rear ~4' of frame all had to be completely rebuilt because it was so rusted away, and virtually every outrigger needed some repairs as the little flange that connects to the bellypan was all but disintegrated.

My point is that plain-jane unsealed plywood lasted 30 or more years, but that the frame was in worse shape than the plywood. So when I did my rebuild, I did my best at preserving the rebuilt frame with POR 15, and installed marine grade (recognised as overkill--something with a smooth top surface would have been adequate) plywood that was entirely painted, top and bottom and edges with about 3 coats of poly. If you replace your floor with some indestructable engineered product, you better rebuild your frame out of stainless steel so that it will last just as long a your floor.

To pervert a well-turned phrase: The price of a solid floor is eternal vigilence (for leaks). It is only 4 years since I removed the shell, replaced the floor and sealed up everything tight as a drum, but already, I have detected a leaking seal around a stack window (that was freshly replaced a couple years back).

So after all of the threads on this topic I have read, I can offer the following good practices that are repeated over and over:
1) "Pressure treated" wood should not be used--same for particle board, chip board, OSB, etc.
2) A decent grade of plywood (with smooth top surface) is just as good as Marine grade for this application
3) Engineered products that are superior to wood exist, but the cost might blow your budget.
4) Anytime wood is used at least the very edges and 6-12" in should be painted with something to seal them up (be that poly, penetrating epoxy, etc.).
5) The trailer has to be maintained and leaks identified and corrected ASAP.
6) Covered storage helps.

Now for some unsolicited advice. I have spent plenty of time looking for the "best" solutions for practically every aspect of my trailer rebuild. What this leads to is months of delay in getting the project complete while I engage in "analysis paralysis" weighing the pros and cons of the different choices. These "best" options also lay the foundation for a slippery slope into overkill--ie., as long as I am using indestructable flooring, I should rebuild my frame out of stainless steel, etc.. Pretty soon that rebuild you thought would be quick and cheap has dragged on for 5 years, you stopped keeping the receipts for your purchases, because you really don't want to know how much money you spent, and you are completely burnt out working on it and pining over every decision.

Good luck!

[slowmover]

Or, how one hopes analysis paralysis is only for a man age 37. Not 73. 😁

[madpiper]

This is the best product if you want something that really works.



http://nyloboard.com/nylosheet/nylosheet-faq

[Wabbiteer]

MDO plywood. 'Medium Density Overlay'. The same waterproof resins used to bond the inner hidden plies together are used to encapsulate the outside veneer under a sheet of brown craft paper similar to the best grocery bag paper stock. So it's pre-epoxyish coated at 40,000PSI~ pressure to drive deep it into the surface grain just like the internal lamination grain.

The data sheets on the MDO I nabbed for my '73 stated it was tested under advertising sign usage in the Everglades for two years with little or no changes when primed & painted, so I primed and painted my floor with the best porch paint I could find. Fall of 2011 I paid $42 a sheet for 3/4" 49 x99" MDO. Shop around.

http://www.olypanel.com/common/pdf/S...it%2011-07.pdf

MDO is also used as concrete forms in heavy construction where they reuse the forms as many times as possible. If you ever want battle tested plywood for some severe duty application find the concrete form paint mentioned in many MDO mill's spec sheets recommendations.

Photo is MDO scrap laying just where its been exposed to sun & weather & puddles all winter (Oct to June) with many freeze-thaw cycles plus 10+ inches of rain this spring. Zero signs of delaminating or overlay decay. Left edge is my cut, right end-grain is factory edge. The gap beneath is not warp, there is a pane of window glass laying beneath the far edge lifting it above the block of graphite.

[Kemblkr]

Exterior grade plywood BCX or better. Before installing and after cutting several coats of spar urethane on the edges and 6-12" around the perimeter. I also did the complete bottom with spar but left the rest to be coated with vinyl cement and then Commercial vinyl planks. I would not be scared of OSB but it needs to be urethaned as well but lean towards to plywood. If plywood gets wet it usually returns to its normal size when dryer. OSB will swell over time but it's really flat which is good.

Just had my hip replaced last week but got the floor down before surgery. Reinstalling everything will have to wait a couple of months.



Sent from my iPhone using Airstream Forums

[Isuzusweet]

Originally Posted by madpiper

This is the best product if you want something that really works.



http://nyloboard.com/nylosheet/nylosheet-faq

A couple of concerns with Nyloboard....It's very heavy and the expansion and contraction rate is a real problem if you don't allow for it. Coosa is very light and doesn't expand or contract.

As for the MDO, if it's anything like the waterproof MDF (Extera) that I have at work it's bloody heavy!!!!

Cheers
Tony

[Al Boondy]

NyloBoard-Ceases-Production/

[Wabbiteer]

MDO is hardwood veneer outer - softwood inner ply plywood with two sheets of paper used to keep the exterior resin layers neat and make that perfectly smooth surface...

Those 3/4" oversized sheet I found (49"x99") were 72~ pounds each +/-normal variation - and the oversize, if you can find it, makes for great lap joints on the lateral seams.

Roughly: MDF would be plus 30%, particle board plus 25%, OSB plus 20% weight... the 'glue' is heavier than the wood...

[rugjenkins]

I used advantec flooring and have been very impressed with it. My biggest concern was engineering issues on the 70s models so I re-engineered the shell/floor/frame/belly pan connection. My floor sits inside a perimeter band and can be removed anytime. Plus I eliminated the overlap issue of the belly pan to shell. I also spray foamed for insulation which helps stop leaks from rivets. Each much make up there mind on which products and ideas that they prefer. Besides most rebuilds occur every 30 to 40 years. That is a long time.

[Tbeck11931]

Rugjenkins
What did you do with the C channel?
If you replaced any of it where did you get it?
Thomas

[putback]

With the benifit of years of hindsight I'll say go to post #21 Belegedhel, print it and post it in the trailer were you see it every time !!!! Sage advice, wish I'd had way back..That said I took the advice of a Maine salt water boat restorer and used "western fir" 5 ply exterior. Sealed it with 50 /50 mix boiled linseed oil & thinner, dried, coated with ureathane. 3 rigs, 3 floors now, one 12 yrs old no problems, even in the tail under the bath room or the entry door. The last two I used no sub floor insulation the last 3 inches of out rigger and bored 1/2" drain holes through c-channel / deck under the windows. No way of knowing if that is usefull, but if the edge rots it won't be due to wet fiberglass insulation.

[angieair]

I bought a '69 globetrotter last spring but haven't done much with it yet except rip out the old carpet and curtains and cushions. The floor by the entrance was rotten.My son, who renovates houses, suggested that I use the backer board you use for tile. Would that work? I need to replace the rotten floor just in front of the door, so it's not a very big piece. He said it wouldn't rot, like plywood. (I know, my problem is leaking trailer! When it warms up a little here in Colorado, I will caulk the vents and other roof leaks, windows, doors, weatherstripping. Do I just caulk all the outside seams?)

[trekerboy]

Originally Posted by Belegedhel

Now for some unsolicited advice. I have spent plenty of time looking for the "best" solutions for practically every aspect of my trailer rebuild. What this leads to is months of delay in getting the project complete while I engage in "analysis paralysis" weighing the pros and cons of the different choices. These "best" options also lay the foundation for a slippery slope into overkill--ie., as long as I am using indestructable flooring, I should rebuild my frame out of stainless steel, etc.. Pretty soon that rebuild you thought would be quick and cheap has dragged on for 5 years, you stopped keeping the receipts for your purchases, because you really don't want to know how much money you spent, and you are completely burnt out working on it and pining over every decision.

This might be the best advice I've ever read on this forum; thank you!

[lawrell]

Has anyone used cedar oil to seal subfloor? Working on 1970's Airstreams and I really dont have the ability to start from scratch so I was wondering if sealing the existing sub floor front the top with cedar oil would be a good idea to help the sub floor. From what I understand, cedar oil petrifies wood but not sure if its effective since I can only coat the top side.

Thanks
Lawrell

[Peter417]

Can anyn of you advantec people chime back in?

[rugjenkins]

Advantec is great stuff. Mine has been installed for 5 years. No issues. I had a few leaks. Repaired and dried area out. For the price it’s a no brainer. But then again since lumber is so high coosaboard maybe cheaper 😳😄 I personally think it should be industry standard.

[Daytonacoupe]

The title of this thread is a misnomer; you'll not ever get a consensus on subflooring material. There are hundreds of pages of opinion, some quite polarized, and the latest materials are well covered; pros and cons.

After a ton of reading and much agonizing I went with Coosa. All upside except the cost. Yep, pricey as F, but at the time marine grade plywood wasn't much less, many thanks to Covid inflation. When I factor in the numerous hours preparing for and doing the shell off on a triaxle, then add the cost and time of epoxy I'd have required for plywood, the extra for Coosa was well worth it. I'm working outside and live on the coast, so where the floor didn't go on with the trailer back together in a day, water that worked it's way through the tarps as I took my time didn't cause anxiety.

The shell was back on the frame just before winter. I had to take a break because high winds and subzero temperatures are not friendly to handling metal tools. I've watched for and identified a few leaks, including condensation in the right conditions. Fridge intake, fridge exhaust, bathroom vent, kitchen vent. Limited anxiety in the short term as the Coosa is not bothered. I'm not minimizing the importance of a totally dry trailer with no leaks, but you'll likely not ever have a 100% moisture free trailer always.

With no interior installed yet I have watched how intrusive wind and precipitation can be. Granted, my plastic exterior wheel wells are only tacked in (fabbing aluminum ones) and the side wrap bellypan isn't on so there are open rivet holes, but snow and rain are sandblasted into every opening, even through the rivet holes. C channel has openings between pieces that are filled with degraded caulking, sloppily butts up against plastic wheel wells that deform over time and create openings. The biggest offender by far is the fresh air fridge vent on the side of the trailer, with the hot water heater a distant 2nd (heater is out and the door was tacked in so less sealed than if the heater was in place). I swept or in some cases shoveled the trailer out after every windy snowfall - we average 30-40 mph winds with horizontal snow here.

Where the fridge fresh air door is hidden from the inside view, I wonder how many trailers experience significant water/snow intrusion through this opening where the owner doesn't even know the action is happening. The battery boxes while towing would be up against hurricane force winds. Add a few mishaps with plumbing; all of this moisture wicks into the channel, under the flooring, or into carpeting, and if trapped by the subfloor material, is not going anywhere.

I think it's clear what's best; how much better continues to be open to debate. There are so many variables on your personal circumstance / use side of the balance sheet.

Before a storm and after - nothing like a photo to illustrate the narrative.

Best of luck with your reno.

Cheers

[CaddyGrn]

Just throwing in my 2 cents here. My husband restored our 63 Bambi 15 years ago and put marine-grade plywood down for the floor. He did use some kind of sealer (verathane) to keep out moisture all along the edges and about a foot from the edge. He left the rest natural to be able to breathe. Whether others have used the same or not, or what you choose is a personal matter. I just want to say in 15 years we have had no problems, and our Bambi is not under cover, but stored in our backyard.