Tabletops Bowing Over Time

[Eddie Ormerod]

Within the last 10 years, I've built many tables.
There's been two times and now a third where after almost a year, the customer has contacted me saying their tips have bowed. All 3 tips have been maple wood.
I didn't use breadboard ends on either of them nor did I use the steel braces on the bottom.
I seal my furniture with oil based polyurethane.
I don't understand if it's something I'm doing or what's going on.
After one top warped 2 years ago, I installed the steel pieces under the top. I think they were c or U channel maybe? Anyway I never heard back from the customer so maybe they worked.
I guess I have to make another top or try the braces. I'm just not sure what is going on here.
And I live in Kentucky.
Any suggestions?
Thanks
Eddie

[Edward Weber]

Need more information than what they're made of and finish.
Do you use an apron or some other type of stabilizing support underneath or are they just slabs.
If it's the latter, they're gonna bow or warp or somehow move out of shape, that's what wood does unless you control the movement by some method.

[Jim Becker]

If these tables are being used in a commercial situation and enduring a constant stream of cleaning cycles, it would behoove you to make the C-channel a standard feature. Also consider how you are holding the tops on whatever is under them...it has to accommodate wood movement, but also disallow any cupping/warping, too, over time. Even "sealed" with the oil based finish, moisture and temperature are still a factor and wood moves because of them.

[Richard Coers]

How did you fasten the tops of the tables to the leg assembly. I've never had a call back on a table, and I've been making them for over 50 years. The size of the top means the wood can shrink from around 1/4-3/8" across the grain. Do you finish the bottom of the top? That's very necessary for a flat top.

[Matt Lau]

Any pictures of your work?

First thing that comes to mind is lack of lateral support.
It's something that Stan Covington strongly advised me on in constructing stuff.

[Eddie Ormerod]

It's a dining room table. I used figure 8 fasteners on top of aprons to the underside of top.

[Eddie Ormerod]

The top is 72x42, 1 1/2 thick. Whole thing is stained and polyurethaned. No c channels or breadboard ends. Mounted to aprons with figure 8 fasteners. I always use those to allow for movement.

[Andrew Hughes]

In my mind a 1 1/2 maple top shouldn’t warp if the wood is kiln dried. So my guess from a thousand miles away is the figure 8s aren’t allowing enough movement. Other reasons I’ve seen wood cup or warp is direct sunlight heating the surface.
Careful selection of wood for table tops are critical too me. A tables top demands the best boards for look and stability
I also think adding c channel to the underside is blasphemy and highlights the craftsman’s lack of experience or confidence.
Good Luck

[Mel Fulks]

I blame the top…or whoever put a safe on top of the top. And a 3 inch thick top would stay pretty flat , unless used for one of those
lady riding a donkey shows.

[Richard Coers]

This is the pinnacle of my career. 4'x12' mahogany and painted plywood.
conference table.jpeg

[Bill Dufour]

Tips? Are the figure eights at 45 degrees to the grain. Screws not too tight.
Bill D

[Eddie Ormerod]

Fasteners were on the ends of the tables. A couple on the linger aprons. Screws definitely not tight

[Eddie Ormerod]

I'm taking your advice and tips. The house is a fairly new built house. Within a couple of years. The table is in their kitchen area. Back in March I dropped it off. She sent me pics of it last night showing the edges raising up.
I'm gonna have to build her another top I guess😭
I just don't know what caused this. It's about the 3rd or 4th one within probably a 100 tables.
I want to send you guys a pic but don't seem to know how.

[lou Brava]

Well if it's only 3 or 4 out of hundred your doing pretty damm good ! & if it's the same table, same wood type, same moister content & construction method & similar climate it's defiantly a head scratcher. I can't see how a figure 8 installed right or wrong would cause a table top edge to raise or warp.

[Edward Weber]

IF, the table is in the direct flow path of a forced air HVAC system, this could have an effect on the top.
Once again, IF the table is in this path, the wood may not be able to recuperate, or balance out before the next heating/cooling cycle begins. This drying becomes slightly greater with each cycle of the HVAC and eventually starts the warping.