Tank Not Well Supported: Insulation BENEATH Plywood To Rectify?

[Kengar]

Has anyone ever used a sheet of insulation BENEATH sheet of plywood on a tubular steel stand (as well as on top of it)?

After two years fixing it (workmanship by Coast to Coast on the eurobracing was pathetic), I finally got my tank downstairs and onto stand. Unfortunately, as you can see, there is some irregularity somewhere which has about a third of the tank not making contact with the decking, and the Homasote material -- CTC's suggestion...... -- is unable to make up for the deviations.

I won't be able to get the tank up off the stand until Thursday to rework things, but eyeballing along the rail of the stand and looking for gaps between the plywood base and the tubular steel has me concerned that the stand itself (purchased from Miracles In Glass) isn't perfectly flat across the tops of all segments used to construct it. Hence, I'm thinking about putting down a sheet of insulation on top of the stand to "absorb" the imperfections; then the plywood; then another sheet of insulation on top. Clearly the Homasote isn't working as it should have. (Did I mention it was CTC's suggestion.........)

Thoughts?

IMG_4629 by Kenneth Fagin, on Flickr

IMG_4630 by Kenneth Fagin, on Flickr

 

[TheEngineer]

Oh yikes!

That homasote board is hard, right? I’d think a sheet of foam would be a better choice. It will allow everything to settle in and make contact. I personally wouldn’t do foam under the plywood without another ply for it to sit on. You’d be relying on just the edges of the foam to hold the entire weight of your tank.

 

[Kengar]

Yeah, it's pretty compacted to begin with.

Re your suggestion about "another ply," I assume you're talking about another layer of foam insulation. That is what I have in mind. Insulation on stand; plywood on that; insulation on top of plywood. Tank.

 

[Flippers4pups]

Let's start at the beginning. Is the stand level and coplanar without the tank on it?

 

[trido]

I'd remove the tank and see if the stand truly is the issue. Have you tried putting a pry bar under the stand on that end to see if it has flex. If so, shim the stand. If its not the stand, shim between the plywood and the stand so the deck is as level as possible. I foam board IMO is good for about 1/32" of variance. Not the 1/8" plus that your looking at.

 

[Flippers4pups]

I'd remove the tank and see if the stand truly is the issue. Have you tried putting a pry bar under the stand on that end to see if it has flex. If so, shim the stand. If its not the stand, shim between the plywood and the stand so the deck is as level as possible. I foam board IMO is good for about 1/32" of variance. Not the 1/8" plus that your looking at.

Duane, this ^ is where I was heading. Good call!

 

[Kengar]

I don't see it as a flex issue.

Re removing tank, that will be Thursday and most definitely will be testing fit between tank and stand first.

Re shimming between stand and plywood, what sort of shims? Strips of metal shimstock, along the rails of the stand, more stacked up where more gap?

 

[KStatefan]

I'd remove the tank and see if the stand truly is the issue. Have you tried putting a pry bar under the stand on that end to see if it has flex. If so, shim the stand. If its not the stand, shim between the plywood and the stand so the deck is as level as possible. I foam board IMO is good for about 1/32" of variance. Not the 1/8" plus that your looking at.

^^^^^^^^^^^^Ditto^^^^^^^^^^^^^^

 

[Flippers4pups]

I don't see it as a flex issue.

Re removing tank, that will be Thursday and most definitely will be testing fit between tank and stand first.

Re shimming between stand and plywood, what sort of shims? Strips of metal shimstock, along the rails of the stand, more stacked up where more gap?

Stand may not be square. Metal shims may corrode. Plastic ones would be better.

 

[TheEngineer]

Yeah, it's pretty compacted to begin with.

Re your suggestion about "another ply," I assume you're talking about another layer of foam insulation. That is what I have in mind. Insulation on stand; plywood on that; insulation on top of plywood. Tank.

I think what you are saying is you want to have this configuration:

Tank
Homasote
Plywood
Foam
Stand

Right?

I wouldn’t recommend the foam sitting on the stand because it will only be supported on the edges.

I agree you need to figure out what is off. I don’t personally advocate shimming the surface of the stand if that’s what is off. I would use foam. That said, if your stand is way out of whack you will need more than foam.

 

[trido]

Composite shims from the local Hardware store will be plenty strong and will not corrode.

 

[Kengar]

Re shims, I think they are more angled than the space permits. gap is about 3/32 over the course of a 3.5-foot length. The composite shims are thicker and more highly angled. What a nightmare....

 

[Kengar]

I think I've identified source of problem. As noted above, screw holding homasote to plywood was contacting steel of stand. On other side, it was even more noticeable how that was causing the plywood to lift away from the stand (rather than just stripping out wood as I continued to turn the screw and it was blocked from advancing by the stand). So, I will obviously need to yank all those screws and only screw down where I am clearly well away from the tubular steel of the stand. (I do think I'm going to replace the homasote with foam (on top of plywood) since it is more compressible than homasote and should compensate for any remaining imperfections.) Assuming the planned fix on Thursday takes care of it, this will be a relief...... I did turn the tank to access and remove a couple, and the wood dropped down into engagement with the stand!

IMG_4637 by Kenneth Fagin, on Flickr