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Pizza Freak 07-16-2008 07:48 PM

Insulation boards not flat...
Hi All,
After working hard to get my hearth slab flat, I find that some of my insulation boards are a bit warped, or curved...essentially not flat. My plan was to lay down the boards on my slab, put on a layer of firebrick, and install the oven on top. Not having that insulation base flat tends to complicate matters.

Has anyone ever tried to flatten out a ceramic fiber board, perhaps by weighing it down on a flat surface (like my slab), or should I return the boards and get a replacement?

To give you an idea, if I lay the worst board on my slab, I get a 1/2" gap between the slab and board.

Thank you all for any advice you can provide.

Les 07-16-2008 08:37 PM

Re: Insulation boards not flat...

Originally Posted by Pizza Freak (Post 37415)

To give you an idea, if I lay the worst board on my slab, I get a 1/2" gap between the slab and board.

Yo Freak (always wanted to say that, kinda like, Hi Jack in an airport)

What happens if you start loading them with the weight of the brick? If thats not the solution, could you trim the high spots off and level it with fire clay? My boards were pretty true - you have a strange situation - who made the product?


RTflorida 07-16-2008 08:48 PM

Re: Insulation boards not flat...
My thoughts are along the lines of Les. Although I have not used the insulation board, from what I've read I would think it to be light weight and have a bit of flex over the length of the board - which the weight of the bricks should should counter....again, I have not used, so I don't know; but it wouldn't hurt to lay out the board and start laying on the hearth bricks and see what happens.


Pizza Freak 07-17-2008 02:24 PM

Re: Insulation boards not flat...
Thanks guys for the reply...

Well, I've decided to try to stack my boards, top with a piece of plywood, and weigh them down with some cement pavers I have on hand (on a flat surface, of course). The board is somewhat resistant to bending, but obviously it was flat to start with and has been deflected in transit, so it must be able to "deform" back into place.

Would it help to wet the boards?

I'm surprised that more people don't have this problem, but I'm a neophyte here.

Thanks for the input!
The Freak

dmun 07-17-2008 02:29 PM

Re: Insulation boards not flat...
What product are you using? Un-flat boards are not someone has reported here before, and quite a few products have been tried.

Pizza Freak 07-17-2008 05:21 PM

Re: Insulation boards not flat...
Hi dmun,
I was hoping that I could find people out there who've dealt with the same situation (if it is common)...and have corrected it. Again, I'm not sure how common this is and how correctable it may be. I think I'm more interested in finding out a solution rather than trying to point a finger at a manufactuer/distributor right now.
These boards seem deformable by nature. I just don't want to procede with my construction unless I feel comfortable with the foundation.

Sorry to be obtuse, but that's where I'm at.

I have a little experiment going with a couple of hundred pounds of weight vs. 4 slightly deformed boards.

I'll report back later!

CajunKnight 07-17-2008 08:41 PM

Re: Insulation boards not flat...
Asking the product you are using was not intended to point fingers. It was intended to help solve the problem. Good luck on your experiment.

Les 07-17-2008 08:58 PM

Re: Insulation boards not flat...
Agreed CK, If there is bad product out there, it serves our group well to avoid it. Then again, if he solves the problem - it's all good :)


dmun 07-18-2008 05:44 AM

Re: Insulation boards not flat...
No intension here to be critical. We're asked about a lot of products, and most of us have only direct experience with one (in my case, insblock19). The more we know about specific products, the more we can help you, and future builders in those cases where we haven't run into that specific product before.

christo 07-18-2008 06:48 AM

Re: Insulation boards not flat...
If the product is deformable, I could imagine that moisture contributed to the deformation - We have one member here who had a bad experience with one type of insulation board that turned to mush when it got wet...

This is a pretty cool forum - and about the best bunch of folks I've ever had the chance to be on a forum with. We are all about helping each other be successful.


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