Will this farmhouse table design have expansion issues?

[Joey Stephenson]

I plan on making a farmhouse dining table for a friend, and wanted to check here first to make sure I'm not overlooking anything. There will be one fat leg on each end with a board on top to secure to the table top. There will be a stringer between the legs towards the feet. Pretty typical design (see image for a very simplified drawing of the type of table). The top will be edge-glued planks.

This design shouldn't have much of an issue with expansion since the stringer and table top, being made from the same species, should expand/contract at the same rate, right? I'd hate to have an issue where the top expands more than the bottom and weakens/cracks joints after a few years.

Table1.jpg

[Mike Cutler]

The expansion and contraction of the stringer versus the top isn't an issue. The grains will run 90 degrees opposite of each other across the face. Stringer will be in a vertical plane, the table top in a horizontal plane.
What you do need to account for is the ability of the table top to expand and contract with the cross members you will mount it to on top of the vertical posts ( legs).
Table irons, sliding dovetails, etc ,will need to be used.

[Joey Stephenson]

The expansion and contraction of the stringer versus the top isn't an issue. The grains will run 90 degrees opposite of each other across the face. Stringer will be in a vertical plane, the table top in a horizontal plane.
What you do need to account for is the ability of the table top to expand and contract with the cross members you will mount it to on top of the vertical posts ( legs).
Table irons, sliding dovetails, etc ,will need to be used.

Good point! I'm not familiar with table irons, what is that?
What if, instead of a single piece connecting board with grain perpendicular to the top, I edge glued planks to make the board in order to put their grain parallel to the table top? Would that mitigate the need for any special connection there, or is that not recommended for strength issues?

[Marc Jeske]

As others said above... There are a number of ways to handle the issue, the common idea is allowing the top to expand and contract independently of the members it sits on.

A simplified explanation below.. with one solution... Marc

http://followyourheartwoodworking.bl...like-this.html

http://www.leevalley.com/en/hardware...=3,41306,41309


More possibilities...

https://www.google.com/search?biw=12....0.aVRysAn0-qo

[Joey Stephenson]

As others said above... There are a number of ways to handle the issue, the common idea is allowing the top to expand and contract independently of the members it sits on.

A simplified explanation below.. with one solution... Marc

http://followyourheartwoodworking.bl...like-this.html

http://www.leevalley.com/en/hardware...=3,41306,41309


More possibilities...

https://www.google.com/search?biw=12....0.aVRysAn0-qo

Great info, thanks. I just realized that I had myself confused about the direction of expansion. I swear I know that it isn't longitudinal. It's definitely a Monday morning...

[Marc Jeske]

Also, you did not say if the top boards were glued up to make a wider one piece top, or left as individual .

The first method, though providing an easier to wipe off top, will be less forgiving if not mounted correctly than the separate NOT glued up board method.

If you mount it as all have said above, you can make your top either way and be safe.

Marc

[Marc Jeske]

If you look up data of different species width vs length ratio of change, it's quite dramatic the difference.

If you are a reader check out R. Bruce Hoadley "Understanding Wood"

Excellent book.

Highly recommended by many here. Marc

[Pat Barry]

I plan on making a farmhouse dining table for a friend, and wanted to check here first to make sure I'm not overlooking anything. There will be one fat leg on each end with a board on top to secure to the table top. There will be a stringer between the legs towards the feet. Pretty typical design (see image for a very simplified drawing of the type of table).

This design shouldn't have much of an issue with expansion since the stringer and table top, being made from the same species, should expand/contract at the same rate, right? I'd hate to have an issue where the top expands more than the bottom and weakens/cracks joints after a few years.

Table1.jpg

I suggest that you should add a couple lengthwise aprons to the underside of the top to increase the rigidity. Otherwise, IMO, the top would need to be much thicker than the sketch shows to eliminate sag and bounce in the tabletop.

[Marc Jeske]

And even more good stuff.... Marc

https://www.google.com/search?q=wood...h=608&dpr=1.56

[Marc Jeske]

I think in post #3 you were talking about "Breadboard" ends maybe?

If so, study how they are attached if done properly as designed for years ago.. - Allowing for movement.
Marc

[Mike Cutler]

Good point! I'm not familiar with table irons, what is that?
What if, instead of a single piece connecting board with grain perpendicular to the top, I edge glued planks to make the board in order to put their grain parallel to the table top? Would that mitigate the need for any special connection there, or is that not recommended for strength issues?

Joey, It's not a strength issue so much as just having to accommodate the wood for what it naturally going to do. That top is going to expand and contract across it's width, no matter what you do. If you don't factor this in, the top will split. Wood moves and there is nothing that can done to stop it.
Any time you have wood that intersects in any plane, meeting at an angle other than parallel with the grains, you have to accommodate for expansion and contraction, and each species of wood has it's own properties concerning expansion contraction, and then the way the wood was milled will have an effect on expansion contraction. Wood workers have been dealing with this since the first two logs were piled up to make a chair.
If it were me, that table top would only be kiln dried, quarter sawn wood, as the expansion contraction across "Q-sawn" wood, is the most minimal, but still there.
Then I would use table irons on the bottom to allow the table to "float" on the cross members, but still be able to expand and contract.
Table irons come in a few different styles. Some look like a figure eight and some a flat bar that has a machined slot in it. My preference is the latter. They are mortised in place with a router, a screw is wet into the top and it then passes through a lip in the iron and the tops is "slid" into the slot. The slot applies downward pressure to keep the table top flat, but the slot in the iron allows the table to expand and contract within the slot. I know it sound difficult, but believe me, they are very easy to install. The cross members themselves could be router to provide exactly the same function as a table iron.

[Robert Engel]

Your only expansion issue will be attaching top to trestle supports -- only if the grain is running lengthwise (which I hope it is ;-).

Many way to allow for that (slotted screws, clips, etc) with just a little Googling.

Do yourself a favor and do the breadboards ends as mentioned.

I would glue up that top right away and give it time to acclimate.

Hope all goes well!

[Joey Stephenson]

Wow, so many great responses. Thank you all for helping out. I should mention that the legs/stringer will be yellow pine for this first table. The top may also be the same, depending on the customer's budget. I was considering alder due to price, but it is just as soft, if not softer, than yellow pine based on the janka scale. Would that still be a better choice?

Also, you did not say if the top boards were glued up to make a wider one piece top, or left as individual .

The first method, though providing an easier to wipe off top, will be less forgiving if not mounted correctly than the separate NOT glued up board method.

If you mount it as all have said above, you can make your top either way and be safe.

Marc

Yes, the top planks will be glued together.

I think in post #3 you were talking about "Breadboard" ends maybe?

If so, study how they are attached if done properly as designed for years ago.. - Allowing for movement.
Marc

No, I just described it very poorly haha. I was talking about the cross members that are pictured under the top, used to connect the table to the legs/trestles.

Your only expansion issue will be attaching top to trestle supports -- only if the grain is running lengthwise (which I hope it is ;-).

Many way to allow for that (slotted screws, clips, etc) with just a little Googling.

Do yourself a favor and do the breadboards ends as mentioned.

I would glue up that top right away and give it time to acclimate.

Hope all goes well!

No breadboards on this table! I'm not quite ready to tackle that yet. Once the customer (more like friend..) has picked the wood for the top, I'll let it acclimate to my shop, cut, and then glue together.

Joey, It's not a strength issue so much as just having to accommodate the wood for what it naturally going to do. That top is going to expand and contract across it's width, no matter what you do. If you don't factor this in, the top will split. Wood moves and there is nothing that can done to stop it.
Any time you have wood that intersects in any plane, meeting at an angle other than parallel with the grains, you have to accommodate for expansion and contraction, and each species of wood has it's own properties concerning expansion contraction, and then the way the wood was milled will have an effect on expansion contraction. Wood workers have been dealing with this since the first two logs were piled up to make a chair.
If it were me, that table top would only be kiln dried, quarter sawn wood, as the expansion contraction across "Q-sawn" wood, is the most minimal, but still there.
Then I would use table irons on the bottom to allow the table to "float" on the cross members, but still be able to expand and contract.
Table irons come in a few different styles. Some look like a figure eight and some a flat bar that has a machined slot in it. My preference is the latter. They are mortised in place with a router, a screw is wet into the top and it then passes through a lip in the iron and the tops is "slid" into the slot. The slot applies downward pressure to keep the table top flat, but the slot in the iron allows the table to expand and contract within the slot. I know it sound difficult, but believe me, they are very easy to install. The cross members themselves could be router to provide exactly the same function as a table iron.

Yes I plan on orienting the wood this way. I'm still having trouble finding information about the table irons (they sound basically like T-slots???) Do you have a link where I could purchase them? I'm having a bit of trouble visualizing this completely, but I get the general idea.

I suggest that you should add a couple lengthwise aprons to the underside of the top to increase the rigidity. Otherwise, IMO, the top would need to be much thicker than the sketch shows to eliminate sag and bounce in the tabletop.

I definitely will do this, I just left them out of the drawing so that the crossmembers/connectors were visible on the legs.

[Marc Jeske]

"Yes I plan on orienting the wood this way. I'm still having trouble finding information about the table irons (they sound basically like T-slots???) Do you have a link where I could purchase them? I'm having a bit of trouble visualizing this completely, but I get the general idea."

Don't my links work ??

Post #4 ? Marc

[Joey Stephenson]

Don't my links work ??

Post #4 ? Marc

Yes I viewed them, but I guess I was expecting something a bit different (and they dont use the "table irons" terminology anywhere that I saw), so I didn't realize that's what was being described. I'm pretty new to this type of work, so I'm a bit slow on the uptake right now! Thanks again.