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It was my first time using a circular saw and jigsaw this past weekend, and I thought I did a decent job creating the 1/2 inch Polyiso template and then the 3/4 inch plywood (solid core) floor. I did 2 coats of poly on the plywood in advance. I left some space around the outside and plan to fill with Great Stuff to secure in place. It’s quiet and doesn’t move or squeak while driving.

However, it is not level :( The difference between the 3 boards is significant enough that I can’t imagine my cork planks (next step) staying flat. Yes, hopefully the Great Stuff will help. And yes, hopefully the weight of rear seats, kitchen galley, bench and bed will help later. But will that be enough? How are people throwing plank floors on top of 3 sheets of plywood?

Mine is a floating floor except for planned Great Stuff. I’d prefer not to do tie downs and honestly I don’t think the tie downs would fix this issue anyway.

I’m feeling discouraged and would love any advice.

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Don't be discouraged there are several ways to fix this;

If you do not want to thru bolt with countersunk bolts, then you could biscuit join & glue the butt joints of the plywood.

It only looks like about 1/4” out at most.

You are right to fix it before the cork flooring.

Did you “stagger” the joints of the polyiso & plywood joint above?
How long has the plywood been laying flat on the polyiso?
Did you coat all 6 sides of the plywood sheets?
 

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yeah, looks like maybe the plywood and polyiso joints arent staggered but are at the same place?

That polyurethaned plywood looks great!!! IMO, I wouldn't bother with the floating floor, no way would it be nicer than your plywood and would weigh a lot and make the floor higher and cost more money.
 

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I removed an inch or so of polyiso at the joints of the plywood. I was then able to place a wood peice under the plywood and screwed the plywood to the piece underneath at the joint. You can then remove the screws in the future if you need to remove a section of plywood floor. The first picture shows the location of one of my joints. The second picture shows the back of my van. I added a wood piece under the edge of the plywood for extra support. I sometimes load heavy things in my van and didn't want to crush the polyiso at the edges.

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I also screwed down the edges for this very reason. Left 1.5" between my XPS insulation and put a 1x2 down, drilled and screwed the plywood edges to it to keep them aligned.

The kreg jig looks pretty neat, but I don't have one and I only have 1/2" plywood floors. I also don't really trust dowel fasteners in the end of glued wood loaded perpendicular to the plane of the laminations. There isn't much load though and you have thicker plywood so that way may be easier if you don't have to remove the panels to do it.

Edit: I also did not bolt down my plywood floor. I know others do, and I'm just getting started, but I can't for the life of me see any reason to bolt it down when it's all connected at the seams and will have various things on top of it and also bolted to the walls.
 

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OP, because you are covering your plywood with the finished flooring layer, you may be able to accomplish what you need to do without removing the plywood (although a biscuit joint as described previously is best). You can take a router with a straight cut bit and cut shallow slots at the seam and utilize a repair plate and some 1/2” flat head screws to join and level the seam. See pic of the plate (also known as a corner brace).
A19EDFFD-A5A0-4C1A-A856-AB6AAFFC3109.png
 

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This is another prime example of why 3/4" is best for the floor! You could use pockets screws (Kreg) if you can get it to lay flat with some extra weight on it. They work great with ¾" stock. Ok with ½" forget anything thinner. The very best way is with glue & biscuits on the butts but, once again, while feasible not great with ½",
‘What is the concern with also using the tie down bolt threads? I used glue, biscuits & the tie down bolts on my ¾" plywood with no spray foam and no squeaks or movement at all.
Trying to reinvent the wheel will only make the job more confusing & add nothing to the final product. Use the correct product and installation method and you will have no problems.
 

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For the OP
Glue and Biscuits! Since you have not fastened it yet this should work. For those beginning, they sell tongue and groove plywood but usually in poorer grades which would need to be covered.
 
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I'm the one above who was in a bind with a glued down 1/2" floor and uneven joints, and ended up using a Kreg jig. The Kreg jig did work out really well and I can report nearly a month later with stable conditions. I've been tromping around with heavy materials, and no sign of weakening. In a few weeks, I'll be putting Marmoleum click cinch tiles over the top.

As others have said, you have the advantage of removing the floor. The sky is the limit on possibilities here. If I had that opportunity, I would have gone glue/biscuits and the factory tie-downs.

Good luck!
 

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Discussion Starter #13
Don't be discouraged there are several ways to fix this;

If you do not want to thru bolt with countersunk bolts, then you could biscuit join & glue the butt joints of the plywood.

It only looks like about 1/4” out at most.

You are right to fix it before the cork flooring.

Did you “stagger” the joints of the polyiso & plywood joint above?
How long has the plywood been laying flat on the polyiso?
Did you coat all 6 sides of the plywood sheets?
I did paint all 6 sides of plywood (2 coats to fully seal). I didn’t stagger the Polyiso and plywood (I used Polyiso as template) but do you really think that makes a huge difference? I’d prefer not to redo the Polyiso if I can get away with it. I do have a biscuit joiner now and I’m going to try it tomorrow! My Dad was telling me though that biscuit joining is great for furniture, etc, but he was worried it could break later if I stepped right on the join. Thoughts? Even if biscuit joining does level everything out, is it strong enough?
 

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Discussion Starter #14
yeah, looks like maybe the plywood and polyiso joints arent staggered but are at the same place?

That polyurethaned plywood looks great!!! IMO, I wouldn't bother with the floating floor, no way would it be nicer than your plywood and would weigh a lot and make the floor higher and cost more money.
I already bought the cork floor long sho so I might as well use it. It adds about 100 lbs, but will give extra insulation. I only did 1/2” Polyiso because I knew I’d get more insulation with cork (otherwise I would’ve done 1 inch Polyiso). Do you really think my lack of staggering makes that much difference?
 

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Discussion Starter #15
I removed an inch or so of polyiso at the joints of the plywood. I was then able to place a wood peice under the plywood and screwed the plywood to the piece underneath at the joint. You can then remove the screws in the future if you need to remove a section of plywood floor. The first picture shows the location of one of my joints. The second picture shows the back of my van. I added a wood piece under the edge of the plywood for extra support. I sometimes load heavy things in my van and didn't want to crush the polyiso at the edges.

View attachment 67491 View attachment 67494
If biscuit joins aren’t strong enough, I may try this method. Does it ruin the insulation effect though with the thermal breaks? Ideally my Polyiso would also be monolith, connected by HVAV foil?
 

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Discussion Starter #17
I also screwed down the edges for this very reason. Left 1.5" between my XPS insulation and put a 1x2 down, drilled and screwed the plywood edges to it to keep them aligned.

The kreg jig looks pretty neat, but I don't have one and I only have 1/2" plywood floors. I also don't really trust dowel fasteners in the end of glued wood loaded perpendicular to the plane of the laminations. There isn't much load though and you have thicker plywood so that way may be easier if you don't have to remove the panels to do it.

Edit: I also did not bolt down my plywood floor. I know others do, and I'm just getting started, but I can't for the life of me see any reason to bolt it down when it's all connected at the seams and will have various things on top of it and also bolted to the walls.
Any concern with thermal breaks when cutting out the Polyiso? Don’t I want the Polyiso to be monolith too, connected by HVAC tape?
 

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Discussion Starter #18
This is another prime example of why 3/4" is best for the floor! You could use pockets screws (Kreg) if you can get it to lay flat with some extra weight on it. They work great with ¾" stock. Ok with ½" forget anything thinner. The very best way is with glue & biscuits on the butts but, once again, while feasible not great with ½",
‘What is the concern with also using the tie down bolt threads? I used glue, biscuits & the tie down bolts on my ¾" plywood with no spray foam and no squeaks or movement at all.
Trying to reinvent the wheel will only make the job more confusing & add nothing to the final product. Use the correct product and installation method and you will have no problems.
To be honest, I don’t really know how to do the tie down bolts. I’d need to align the holes, have a tool that makes holes (which I don’t have), and get long thread bars. I thought filling the edges with a Great Stuff seemed easier? We will soon see :)
 

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Discussion Starter #19
For the OP
Glue and Biscuits! Since you have not fastened it yet this should work. For those beginning, they sell tongue and groove plywood but usually in poorer grades which would need to be covered.
I’m trying glue and biscuits tomorrow! Any tips for the actual process? Can it be done inside the van? Or best to join all 3 pieces outside and move into van as huge monolith? (I’m not sure I could carry it, even with help). How to clamp? How to do it without damaging the Polyiso underneath?
 

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Discussion Starter #20
Glue and biscuits works best for us but may not if poly and ply not staggered
Even if Polyiso is foil taped at seams below, you still think my lack of staggering will make a huge impact? I’m planning to try biscuit joins tomorrow.
 
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