How to repair warped table top?

Page 1 of 2  
Planks (a light wood?) that make up the top of a small table are weather warped. "Cupped" upward.
This isn't meant to be a centerpiece of the home, but it would be nice to make it presentable again.
What's the usual repair recommended for such a condition?
Tools available: the usual drills and hand tools; table saw; router; belt sander; palm sander; paint gun and compressor.
Suggestions welcome.
Thanks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Paul Conners wrote:

Replace the boards. And put them so if they cup they will cup with the center up. Fasten in the center and keep painted/varnished. _____________

Well, you could ....
a) plane down the boards to make them flat on the surface
b) if thin/narrow enough, bend them down and fasten
c) if not thin enough, remove and rip one or more kerfs on underside, put glue in kerfs, bend flat.
--

dadiOH
____________________________
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Depends on the amount of cup and the edges of the table. My wife inherited an attractive elm claw foot from her mom. It had a similar problem and one of the glue joints had failed too. I removed it from the legs, removed the edge trim, sawed through the failed glue joint and glued it back together. Before gluing I took a thin pass through a thickness planer to level the top out again. Came out looking good. If you don't have a planer, search around for a friend or school that does.
RonB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Very hard to say how I would address it without seeing a picture. Can you post a pic somwhere? Be careful if you plan to try and address it with a planer because depending on the defect the planer rollers can sometimes just hold it flat while it planes it, then aftewards it rools right back into it's curl and you have a nice flat but curled surface still.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/17/2012 12:55 AM, Paul Conners wrote:

I like to start this type of conversation by saying, "you're not happy with it the way it is now, are you?" or "it doesn't work now, does it?". I guess we can't hurt too bad.
I would remove the top. On a nice spring day I would lay it on the grass with the humped side up. Let it sit there a day preferably with some sunshine. The piece has probably gotten wet at some point and the top dried quicker and pulled the warp. I am suggesting you try to equalize the moisture throughout the piece. I'm thinking you will see some substantial improvement after a day of absorbing ground moisture on the shrunken side and air/sun drying on the top side. I would them give it lots of weight on a flat table surface, not on the concrete patio or garage floor. After a week, see what you have.
--


___________________________________

Keep the whole world singing . . .
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I like your suggestions. The lawn and sunshine are readily available. But the only large flat surface is the garage floor. And weight? Hmm... 2 front wheels of the Toyota come to mind...
Thanks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/18/2012 12:42 PM, Paul Conners wrote:

I thought his suggestion ingenious as well. How about that Toyota, an appropriately-sized sheet of 3/4" plywood (make a sandwich of your "moistened" top) and a piece of 2x10 as a caul?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In typed:

Find someone with a planer and have them smooth it out for you into a flat surface.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Paul Conners wrote:

Just a note - cupping takes place towards the moisture not away from it.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Just to clarify: the concave side is moist, and the convex side is dry?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Paul Conners wrote:

Yes. Table top looks like a U (not as drastic I hope). Top got wet while the underside remained drier. When it dried out the compressed fibers (caused be the dry side restricting even swelling of the wet side) distort it... according to the books :)
As mentioned, a possible sollution is to wet it all down lay it on stickers and put weight on it to dry.
The "proper" method for an antique is to router out the underside and replace with hardboard. That leaves the original top surface while providing a flat base for it. Something I probably would not have the nerve to do.
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/22/2012 12:05 AM, Michael Joel wrote:

Not necessarily ... and AAMOF, and depending upon the grain and the way the wood was cut off the tree, it more likely to be just the opposite of what you stated ... the concave side being the dry side, and the convex the moist. :)
There are indeed some exception with certain grain patterns due to the way the wood was cut from the log (plain sawn, rift sawn, etc.), or if laminated, but mostly wood cups and checks parallel to the grain and to the drier side.
Excellent example is the cupping of hardwood floors, which "cup" (concave side up) when wet from the underneath ... dry on the top, wet on bottom ... one of the main reasons why a moisture barrier is always used _beneath_ a hardwood floor.
Another hole in your balloon ... leaving a board to dry out in the sun, The concave side is drier from exposure to the sun and heat, and, once again, the board generally cups toward the dry side.
Try this by laying a board on wet grass before the morning sun hits on sunny day, check it out by noon. :)
Here is indeed, "according to the books": http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_16.pdf 16-6:
<quote> Wood warmed by the sun experiences a virtual RH far below the ambient RH. The surface dries faster than the rest of the lumber. This is why cupping and checking often occur on decking boards; the top surface is much drier than the rest of the board. Shrinkage of the top surface commensurate with this dryness causes cupping and checking parallel to the grain </quote>
--
www.eWoodShop.com
Last update: 4/15/2010
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Swingman wrote:

Sorry but I believe what I said to still be right.
While grain of course will have effects the cupping will take place towards the moist side (or away from the compression pressure might also be a way to say it). Take a look at porches or decks, do you seen any cupped down? Fave you ever found a table top that cupped down?
Your wood floor - is it cupping because it is moist underneath or because of the mopping and drying taking place above? as for the board on the lawn - don't know, would have to try it.
Your quote - Is it indeed the sun causing the surface to dry faster or is it in fact that the problem is not visual until the surface dries?
I will explain it as one of the books due (please recall I said this was according to the books - not neccessarily the truth - I believe much of the things "known" are not the truth of what is happening, but only what we as humans can guess at/or comprehend with our limited knowledge).
Wood cells normally want to swell and then shrink back to their normal shape and size. When something restricts this the swelling continues on uncompressed sides (i.e. the bottom of the board, or anywhere else it is not wet/or drier). This forces the cells into more of an oval shape instead of their original shape. When they shrink from drying this shape is not shanged so the compressed sides of the cell (we will call it the width) ends up smaller than it used to be. As this is repeated we end up with cupping/warping/checks/etc..
I can never recall seeing a board that was cupped in any direction except on the side effected by changes in moisture.
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/22/2012 1:09 PM, Michael Joel wrote:

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_16.pdf
Did you bother to even read the supporting evidence I provided disproving your unequivocal contention, first above?

It is indeed "not necessarily the truth", as I clearly outlined above, complete with a cite as to the an explanation for why your statement is not necessarily the case.
By all means, offer a cite that supports your contention to the contrary.

Yes, and as a result, that attitude arguably insures that your knowledge in this regard will remain limited.

The above is either so poorly worded as to be useless in defining your contention, or the result of a total misunderstanding of the effects of moisture and humidity on the dimensional instability of wood.
It's really impossible to tell which?

Again, too loosely worded to be of much use in defining the problem ... and your admission that you have "never recalled" seeing that, is certainly no proof of your argument.
Yes, it is indeed this _differential_ in moisture content between opposite faces that causes the phenomenon of cupping, but not necessarily for the reason you unequivocally stated first above.
Simply put, cupping is most often the result of the opposite (convex) side being moist, and the cupped (concave) side being drier ... the exact opposite of your unequivocal statement.
IOW, your understanding is mostly backwards of the actual effect of moisture on wood, with the exceptions I noted above. You will certainly want to do your homework, and provide some supporting evidence to the contrary, if you want to continue a reasonable discussion of the issue.
--
www.eWoodShop.com
Last update: 4/15/2010
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Swingman wrote:

Ok. Whatever you would like to make it. I have no need to argue. I think my sentences were clear enough.
You also call into question whether or not I even undestand moisture - and that I will not be able to learn (if I don't).
I do believe for some reason you feel offended and seem to have a chip - but that is fine too.
You have decided what you will take for the answer - nothing I say or do will change it.
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/22/2012 2:19 PM, Michael Joel wrote:

To the contrary, and unlike you ... I will certainly read any supporting evidence you have to support your position.
:)
--
www.eWoodShop.com
Last update: 4/15/2010
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/22/2012 1:09 PM, Michael Joel wrote:

Have you ever seen deck boards or a table top that was not attached? Given restrictions a board will bow in the direction that is not restricted. Given no restrictions the surface absorbing moisture will expand and that will not result in a concaved surface.

Absolutely the underneath side. You mop it and water goes down inside the cracks to lower and side sections of of the board. Those surfaces stay wet longer than the top surface. Then the edges expand and they cut up but the surface has long since dried because of exposure.

You are not thinking about all of the surfaces that have actually gotten wet.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Swingman wrote:

> SNIP
Just 2 mor cents...
Grain of course plays a part is how the reaction takes place, but as you said "but mostly wood cups and checks parallel to the grain and to the drier side".
As my previous post metnions - never seen a floor/table/deck cup down.
But I don't want to argue it. As said - I am simply repeating it from information I have read. I doubt anyone knows for sure the real reasons for it all. Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/22/2012 2:11 PM, Michael Joel wrote:

You don't want to argue because you were mistaken, charitably, either in your wording, or your understanding.
And you are very mistaken in your contention that you "doubt anyone knows for sure" ... a first semester, college level, Botany 101 class would prove to you that this is well understood, and well documented with empirical evidence.
For your future benefit, and so this ends on an instructive note, you will certainly want to explore the definitive work on the matter:
(Amazon.com product link shortened)
Every woodworker can learn something from reading Hoadley, guaranteed.
--
www.eWoodShop.com
Last update: 4/15/2010
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Swingman wrote:

See - that is why I get pulled back in. Because the logic is so illogical.
If I said I don't believe they really know what is happening - you say take a "first semester, college level, Botany 101 class would prove" - The only thing it would prove is they believe it. Very circular thinking (as the "scientists" would say).
That will be the last think I desire to say on the subject to you. You may continue to deride me if you like.
Mike
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.