mdf laminate question

I am building a router table, using 2 3/4" MDF panels for top. I have enought laminate only for one side. Is it sufficient if I use laminate on the top surface and seal the bottom with poly? Concern is uneven moisture absorbtion due to differences in surface finish.
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Chris wrote: >I am building a router table, using 2 3/4" MDF panels for top. I have

Did the same on my router table, except no poly on the bottom, and it's stayed remarkably flat for a couple years now. . But I live in the Sonoran desert. I'd go for it, and seal the sides as well. Tom Someday, it'll all be over....
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Chris Carruth wrote:

Your concern should shift to that of an unbalanced construction, the real reason you'll have a potato chip for a router top should you not laminate both sides.
Actually, with a piece so small you can "maybe" get away with it depending on how well you secure the top to the base below. It's hard to say though with the limitations of the information.
UA100
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"Chris Carruth" wrote in message ...

Chris,
if you use poly on the bottom you risk getting some on the edges which will cause them to swell slightly. To avoid this you might shellac or poly the mdf before you cut it to size. Also, if you fix anything to the edges to stop them from swelling, consider how you do it carefully. Any fasteners that are not properly predrilled may cause the edges to raise up where the fastener sits. Any glue may cause the same effect. Some of the plastic edge preparations can also cause the edge to raise.
Greg
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It'll be fine with or without the poly. The idea behind sandwiched lamination is that veneers move with changes in humidity. Commercial laminates are very stable and do not present this problem. Have you ever seen a kitchen counter with the bottom laminated?
Hope that helps you
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Secret Squirrel wrote:

Actually the "idea" has to do with balancing the construction.

Not really so. Using contact adhesive with any laminate (we are talking plastic laminate and not veneer) will creep with most any product no matter how commercial they are.

On a cheaper installation yes. The reason this isn't quite as big a problem is that the counter is typically secured at every cabinet and sometimes in between. The weight of the cabinets does present itself as something the unbalanced counter can't over come so it stays relatively flat.
UA100
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As the old adage goes, "Anything worth doing is worth doing right." I suggest that you get some more laminate for the bottom and attach it the same way as the top laminate is attached - if you know. You will have only one time to do it right. Hoyt W.
Chris Carruth wrote:

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I'd laminate the bottom too. Go to HD or some other place that deals in laminates for the masses. I suspect you can find a piece someone ordered and didn't pick up or returned for a song. For the bottom it doesn't matter what it looks like. I've done this several times.
RB
Hoyt Weathers wrote:

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More than likely, it will warp at least a little. Okay for a table, but not a router table. With the time and effort you have in the router table and the fact that you want it flat, why take a chance.
Preston

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