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Discussion Starter #1
Just got my PM and am ready to start working on it. The previous owner of my PM had 3/4" plywood down and every time I hit a small bump the floor jumps and smacks back down. A little jarring. I'm getting ready to insulate and rework the subfloor and wanted to know if anyone secures the plywood to the van floor to prevent that bouncing noise? If I mount the tie-downs on top of the plywood would that hold it in place enough to not bounce? Looking for options. Any insight would be greatly appreciated.
Thanks,
Shaun
 

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I have a factory floor and it's held down with RztV I believe (or something similar). Ed is correct, just use the tie down bolts to hood it down
 

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I used the factory tiedowns to hold my 1/2" plywood in place, and then started building my layered floor on top of that. I have 1.5" aluminum extrusions (80/20 stuff) as a grid on that, so everything is tied together, have had zero problems with anything moving around.
 

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I believe insulation should go under the heavy plywood. On my van I used luan topped with 1/2 inch insulation then topped with 5/8 hardwood ply. I replaced the factory tie downs with longer metric bolts with fender washers thru the sandwich. In addition I used 10 to 15 self drilling/self tapping TEKS fasteners about 2 1/4 inches long installed in middle areas and near the doors as the factory tie down points along the edges are not sufficient in my opinion. This made a secure base for me to screw down most of the interior camper build.
 

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The bolts are M8 in size. I just did this job yesterday using the original tie down hardware but with the longer bolts. I used bolts that were 2" long to make up for the additional 3/4" polyiso that I have under my factory floor. I made a 7/8" spacer out of 1 1/4" ABS to provide support for the plastic ring/shroud that sits under the tie down. I also added a washer. Since the polyiso is adhered with Great Stuff I feel these 8-10 tie downs will be more than sufficient to secure the floor, especially as the rest of the build will sit on top of the floor.

Shaun, welcome to the forum, not only do we share a name, but our builds will serve similar purposes. I don't think you have the factory floor, but I would strongly suggest putting polyiso on metal floor sandwiched under the plywood. Insulation is best taken care of before you start building the fun stuff.

ShaunB
 

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I put down 1/2" polyiso, then 1/2" polyed birch plywood. I used the van tiedowns but like someone else said, I found they were not sufficient to pull the entire floor down tight and level. I think I added an additional 9 or 10 countersunk bolts through the floor with large washers on the underside of the van. I may still add one more. The hardest part about using the original tiedowns is that you don't have access to the holes from the bottom except for two. So you have to measure from above and hope you hit it. My thoughts are if my floor is extremely secure it'll be better for keeping everything else attached to it secure.

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I went a little different route than everyone else and the only thing I regret so far is not extending a couple of the tie downs, at least in the back.


I used Loctite PL Premium glue to attach my insulation and 3/4 plywood to my van. No mechanical fasteners at all and I have had no issues in the last 9-10 months and thru the winter. Now I insulation I used was a very ridged sound panel made out of foam that were extra on a project we did at work. Was actually used to make these sound proof rooms for Google in there offices. we ill glued those to the floor (2'x4' pieces) than I glues 3/4 plywood to the top of that and made thresholds with aluminum angle. I used about 6-8 large tubes of the glue for the whole floor and so far its been holding up great. I may attempt to pic up a couple of the recessed sprinter d rings like pictured above and locate the factory holes and cut them in.


There is some videos on youtube of people cutting little strips in between every rib to level the 2 surfaces and I see that as unneeded extra work. I put my insulation right over the high ribs and I have no flex at all in my floor. The ribs are so close together and the weight gets so spread out I don't see the foam ever crushing but that's just my opinion.
 

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Discussion Starter #11
Wow... ALL great info! Thanks everyone.
I think I'm going to lay down some polyiso as an insulation barrier then put my plywood back on top. I'll probably use the tie downs and most likely do some self tapping screws here and there to make sure it's secure and level.
Much appreciated!
 

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We did not 'formally' secure our 1/2" polyiso and 1/2" birch plywood to the van. But but by the time we completed the 3-section bed, the galley, the dinette bench and raised dinette floor, and the frig - - most held to the van floor through the otherwise 'floating' poly/plywood - - the floor isn't going anywhere and shows no signs of bulging.
 

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Wow... ALL great info! Thanks everyone.
I think I'm going to lay down some polyiso as an insulation barrier then put my plywood back on top. I'll probably use the tie downs and most likely do some self tapping screws here and there to make sure it's secure and level.
Much appreciated!
Just a heads up, my plan was to use the self tapping tek screws that seapro used but couldn't get them to bite and hold. I feel much better having used the bolts with large washers under the van. Just use a forstner bit and recess the head.

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I had no problems with getting TEK screws to hold. I drilled the countersinks first then drilled the screws in. I aimed to hit high spots of the ribbed structure. You need to push down hard on the drill to penetrate the metal. Once the screw drills into the metal and pulls down stop drilling or you strip the threads. I also used that type of screw holding stuff to the van walls without problems.
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I had no problems with getting TEK screws to hold. I drilled the countersinks first then drilled the screws in. I aimed to hit high spots of the ribbed structure. You need to push down hard on the drill to penetrate the metal. Once the screw drills into the metal and pulls down stop drilling or you strip the threads. I also used that type of screw holding stuff to the van walls without problems.
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You have to drill the countersinks first. I didn't on my the test screws. That was the problem. Any reason why you didn't just use regular self tapping screws?

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Regular self tapping screws thread through the wood then the metal and then as they tighten down they jack the wood up away from the metal and/or strip the thread made in the metal. Also regular self tapping screws have a course pitch thread; TEKs have a finer thread which works better in the hard but thin metal. The TEK screws work differently as they have a tiny wing just below the threads and above the drill point.

You first drill only the cone shaped countersink. Then you drill the TEK through the wood from the base of the countersink. The wing makes the hole through the wood slightly larger than the threaded shaft of the screw and you keep pushing down hard on the machine. The drill point penetrates the metal, the wing breaks off and the screw threads into the metal. As it does it pulls the wood/insulation sandwich down tight and you stop before the threads strip in the metal. The secret is that the hole through the wood is very slightly larger so the screw is not trying to thread in the wood.
 

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I have 3/4" ply over a sheet of Polyiso. I used all of the threaded tie down points and added several additional bolts drilled through the floor. I used flat head tapered type bolts that recess flush with the floor. Like mentioned above, drilling the holes correctly for the tie down points took some measuring but the other bolts were easier - measure the right location and drill up from the bottom.
 

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Reading floor builds with interest as my turn will be coming up shortly.

I like the idea of gluing all layers, polyiso to metal floor with plywood base glued to polyiso.
This is certainly the strongest, most rigid and least likely to squeak designs.
I like it a lot.

Can anyone think of a reason why the base floor would need to be removed ?
Molding due to water leaks? Need to access buried utilities, electrical, plumbing ? best not to bury that of course.
Road accident requiring removal of damaged floor to be replaced when restoring inside?

I strive to have as much access as possible for maintenance, repairs and changes over time leaving room for future needs.
Gluing the floor goes against that BUT the mechanical advantages of a solid floor are hard to overlook.

How difficult would it be to tear, scrape the flooring should it need to come out.

I think if I decide on this method, and think I will be, I would generously paint and seal anything made of wood down there inside and out and use beefy wood support as insurance.
Top layer would need to be easily replaced as that usually wears over time.
 
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