This issue makes interesting reading about what is really legal, but I suspect that if the squirrel house discussed is that saleable there is already...
I've done a bunch of veneer work, on different substrates, without backer veneer. You need to consider how much that backer will move with moisture....
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The local station I mentioned has both on-road and off-road diesel. The price difference is notable because the on-road tax is not on the off-road...