# 10 Foot Long Dining Table Design Question



## aaronww (Dec 17, 2017)

Hey guys, I'm hoping this is the right place to ask this. I'm building a really long farmhouse table, bench and six chairs for a customer and they are pretty set on no extensions or leaves to get the full 10-foot length. They also liked the look of timber framing closer to the end as some other tables they have seen online.

My question is in regards to support in the middle... Should a table with about a 1-1/2" thick top, need a center support? The end supports are 96" apart from outside to outside. What are your thoughts? I've posted an image from SketchUp to help show what I'm trying to do.

Thanks!
Aaron









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## woodnthings (Jan 24, 2009)

*Yes, I probably would, but ...*

A center support, actually running down the center to prevent sagging is what I would do. Aprons on the sides will destroy the original farm house look and become knee and thigh knockers. You do realize that by having the end supports so close to the ends, it rules out seating off the end...? You could point that out to the customer for feedback, if you haven't already. I would duplicate that center support in the leg brace below having the timber oriented vertically for strength of course. :wink:


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## Steve Neul (Sep 2, 2011)

It would take a very long time before there would be a noticeable sag in the table but it would eventually happen without a center support. You could put a couple pieces of 1 1/2" angle iron down the length of the table and put a 1 1/2" wide skirt in front of it to hide it.


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## GeorgeC (Jul 30, 2008)

Does your customer intend to have anyone sit at the end of the table? If so, you need to move your center supports closer together. Twelve inches of leg room are insufficient. I would want at least 18".

George


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## Toolman50 (Mar 22, 2015)

GeorgeC said:


> Does your customer intend to have anyone sit at the end of the table? If so, you need to move your center supports closer together. Twelve inches of leg room are insufficient. I would want at least 18".
> 
> George


I agree. If the trestles were moved inward, there would also be less concern for the center support.


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## aaronww (Dec 17, 2017)

Thank you guys! You're all very helpful. I'll pass these ideas on to my customer and go from there. She likes the look of the trestles close to the end but wanted them a little inward in case they needed to add seating on the ends. That's why they're in 12" from the edge, but I passed on the 18" idea for legroom and placing a third trestle in the center. I might need a second beam running along for support on the trestles to stay vertical, at least that's what I'm understanding from the first reply.

Thanks guys!
Aaron 

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## FrankC (Aug 24, 2012)

Sorry, but seeing Farmhouse Table first thing I have to ask is if are you using breadboard ends?

A support beam down the center will help, one or two cross supports would not hurt either as long as they are not obvious, perhaps consider adding a bit of steel to the design.


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## aaronww (Dec 17, 2017)

FrankC said:


> Sorry, but seeing Farmhouse Table first thing I have to ask is if are you using breadboard ends?
> 
> A support beam down the center will help, one or two cross supports would not hurt either as long as they are not obvious, perhaps consider adding a bit of steel to the design.


Hey Frank, yes I'll be doing breadboard ends. 

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## woodnthings (Jan 24, 2009)

*Just to be clear ...*



aaronww said:


> Thank you guys! You're all very helpful. I'll pass these ideas on to my customer and go from there. She likes the look of the trestles close to the end but wanted them a little inward in case they needed to add seating on the ends. That's why they're in 12" from the edge, but I passed on the 18" idea for legroom and placing a third trestle in the center. I might need a second beam running along for support on the trestles to stay vertical, at least that's what I'm understanding from the first reply.
> 
> Thanks guys!
> Aaron
> ...


I am suggesting a center support like a spine, running down the exact center of your top and attached from below. Because wood moves across it's width, any supports including breadboard ends will have to allow for that movement, either by elongated holes in the wood OR by Z clips in slots in the case of aprons. Breadboard ends will need additional space on either side of the tenons to allow for movement, about 1/16". 

By using a support in the exact center, there is no movement issue.
The center spine under the top could match in size and length the lower support on the trestles. Do NOT use a center trestle, it's not needed.


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## aaronww (Dec 17, 2017)

woodnthings said:


> I am suggesting a center support like a spine, running down the exact center of your top and attached from below. Because wood moves across it's width, any supports including breadboard ends will have to allow for that movement, either by elongated holes in the wood OR by Z clips in slots in the case of aprons. Breadboard ends will need additional space on either side of the tenons to allow for movement, about 1/16".
> 
> By using a support in the exact center, there is no movement issue.
> The center spine under the top could match in size and length the lower support on the trestles. Do NOT use a center trestle, it's not needed.


Alright. Thank you woodnthings! 

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## enzobindo (Jan 2, 2018)

I'm a novice here. What is a breadboard end?


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## aaronww (Dec 17, 2017)

enzobindo said:


> I'm a novice here. What is a breadboard end?


A breadboard end is when your lengthwise boards have tenons which fit into a mortise on a perpendicular board on each end. They're usually pegged in place I think but the holes in the tenons are wide as well as the mortices so they allow for seasonal movement. 

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## Tool Agnostic (Aug 13, 2017)

enzobindo said:


> I'm a novice here. What is a breadboard end?


The novice answer is that you put a narrow board on each end, called a breadboard. The grain in the top runs the long way. The grain in the breadboards run from side to side, perpendicular to the rest of the table (or cutting board). 

If this is your table -> |=====|

... then the breadboards are those vertical lines "|" at the ends.


Here are the more advanced concepts that @aaronww was explaining:

Wood expands and contracts with temperature and humidity changes. Those expansions and contractions happen in every direction except the grain direction. If you hold a board vertically so that the grain runs up and down, then most of the expansion would be left and right and forward and backwards (in and out), but almost no expansion up and down with the grain. 

Serious problems can happen when you have most of your table with the grain running the long way, and then you glue _one full side_ of each breadboard to the ends of the table. When the wood expands, the long central part of the table will try to expand mostly sideways, but the glued on breadboards will prevent it from expanding because the breadboard grain points a different direction, one where there is minimal expansion. The middle wants to expand, and the breadboard ends are glued to prevent it. The pressure builds up and cracks appear in the wood table.

See this thread for more about breadboards and what can happen if you don't compensate for wood expansion. Check out post #19 in particular, which shows how to set up the dowels and slots that aaronww described:

http://www.woodworkingtalk.com/f2/new-member-here-tell-me-what-i-did-wrong-cause-top-fail-189650/

P.S. Here is one of my first projects. It is a cutting board with breadboard ends. I didn't know enough about wood expansion when I built it, so I glued the full length of the breadboards to the rest of the cutting board. I made it as a gift for my in-laws. Once I learned about expansion, I told them that it might crack, and if it did, I would build them a new, better one that compensates for wood expansion.

http://www.woodworkingtalk.com/atta...-board-thickness-suspension-cutting-board.jpg


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## Tennessee Tim (Dec 15, 2010)

Quote......Here are the more advanced concepts that @aaronww was explaining:

Wood expands and contracts with temperature and humidity changes. Those expansions and contractions happen in every direction except the grain direction. If you hold a board vertically so that the grain runs up and down, then most of the expansion would be left and right and forward and backwards (in and out), but almost no expansion up and down with the grain. 

Serious problems can happen when you have most of your table with the grain running the long way, and then you glue _one full side_ of each breadboard to the ends of the table. When the wood expands, the long central part of the table will try to expand mostly sideways, but the glued on breadboards will prevent it from expanding because the breadboard grain points a different direction, one where there is minimal expansion. The middle wants to expand, and the breadboard ends are glued to prevent it. The pressure builds up and cracks appear in the wood table.

See this thread for more about breadboards and what can happen if you don't compensate for wood expansion. Check out post #19 in particular, which shows how to set up the dowels and slots that aaronww described:

http://www.woodworkingtalk.com/f2/new-member-here-tell-me-what-i-did-wrong-cause-top-fail-189650/

P.S. Here is one of my first projects. It is a cutting board with breadboard ends. I didn't know enough about wood expansion when I built it, so I glued the full length of the breadboards to the rest of the cutting board. I made it as a gift for my in-laws. Once I learned about expansion, I told them that it might crack, and if it did, I would build them a new, better one that compensates for wood expansion.

http://www.woodworkingtalk.com/atta...-board-thickness-suspension-cutting-board.jpg[/QUOTE]


Tool agnostic.....pretty close ....let's clear it on up though.....You're on track with movement BUT which direction needs addressing... .the cracking is actually from the contraction/shrinkage (loss of moisture) as both outer edges are holding from the glued breadboard and the crack is the weakest point in the "link" in the shrinkage. USUALLY in the swelling/expanding (gaining of moisture) will result in a cup or a bow BUT that all depends on how other parts are fastened.

This is a quick reference.... it is complicated BUT learnable. Have a good day.


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## GeorgeC (Jul 30, 2008)

CANNOT READ PURPLE.

George


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## 35015 (Nov 24, 2012)

Hey Aaron,

Just ran across this over coffee this morning...

Great project and I loved your preliminary design for your clients project!!! Of the last 10 tables built (and most I have ever built) they have all been of this design style in truly the folk traditions....and...out of green wood as they would have typically been built historically. I have seen examples in several regions, both here in collections and in Europe (et al.) In its generic varied forms, it is without a doubt one of the most functional work and dinning table designs available, well proven over millennia of applied use, as the "Farm Table" can be dated back to over 7000 years ago, with little difference in what we would see today.

I will try and hit some highlights, and look forward to any other query you may have on this favored subject...:vs_OMG:



> My question is in regards to support in the middle... Should a table with about a 1-1/2" thick top, need a center support? The end supports are 96" apart from outside to outside. What are your thoughts? I've posted an image from SketchUp to help show what I'm trying to do.


Over 2.4 meters (~8') I kick mine up to a full 50mm (2"0) sometimes 75mm (3") depending on intended use...e.g. strictly dinning or is it going to be a kitchen work table as well.

As others have pointed out...sitting at the end of the table will indicate the method (or need) for a Central Bridge Truss between the end Support or Leg Truss work, as well as some other factors. Many have Central Bridges...Many do not and function just fine without them. It all depends on the end use, species/quality of wood, and desired affect wanted in the table's overall appearance. The largest/longest I have been part of building and/or facilitating was over 7 meters (~24') and over 2 meters (~4') wide out of book matched slabs of White Pine, all wood joinery, and again...greenwood. This one did have a single (many have double) Central Bridge, and mid-span Leg Truss work as well.

Great CAD design over all, and my critique of it would only be in alternative style/design parameters. As a teacher/facilitator, unless I see something out of overall context, I don't like influencing someones "design flavor." In your case, Its really a great design with a strong French/Spanish flavor.



Steve Neul said:


> It would take a very long time before there would be a noticeable sag in the table but it would eventually happen without a center support. You could put a couple pieces of 1 1/2" angle iron down the length of the table and put a 1 1/2" wide skirt in front of it to hide it.


It does take a very long time...and often not at all depending on thickness of top. Many of these historic tables are over 2.5" thick. Many do have a slight swoop to them but nothing overly detracting from their function or use.

The application of a metal angle is not the way they typically where built and is out of context in most designs unless of some Germanic and Old English versions I have seen with wrought iron wedge strapping and other metal elements. I would also make note (as I have done restoration work on some) that angle iron even as large as 3" in spans over 8' can develop "sag" to the point that some clients take umbrage at it...Skirting on these tables typically do not exist, and again, 1 1/2" would sag/warp with a top that is undersized for the span...

Aprons, when they do exist are 4" minimum, and the Central Bridge Truss work is never smaller than 150 mm (~6") and only go up in size and robustness from there in my experience with this wonderful folk style of table. Central Bridge work here comes in many styles and designs. Often with visible joinery systems that are both functional and pleasing to the eye. 




> She likes the look of the trestles close to the end but wanted them a little inward in case they needed to add seating on the ends. That's why they're in 12" from the edge, but I passed on the 18" idea for legroom and placing a third trestle in the center. I might need a second beam running along for support on the trestles to stay vertical, at least that's what I'm understanding from the first reply.


Many clients like the more rustic versions of these Farmer's Tables with the exposed joinery being very visible. It does make sitting at the end of the table more of a challenge, but still doable in most cases even with only a 200 mm (~8") set back. In some designs there have been (I've done a couple myself) a removable "Bread End" that can effectively extend the table should the need arise.

In closing I would also note (especially in the tradtional styles and method of building) this table design is...ALL WOOD JOINERY...no glue...no hardware of any kind. This is the reason the table can be made of green wood as they have been for millenia...You got to love folk style building!! :grin::grin:

I should add, as a point of interest...when designed and built as intended, the originals could be competently disassemble with some ease...Including the large top into single board/planking. Another nice feature of traditional design, joinery and method of building...Makes transport a lot easier to boot!!! :wink:


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## Tennessee Tim (Dec 15, 2010)

Tool Agnostic;1853674
.......
Here are the more advanced concepts that [USER=175858 said:


> @aaronww[/USER] was explaining:
> 
> Wood expands and contracts with temperature and humidity changes. Those expansions and contractions happen in every direction except the grain direction. If you hold a board vertically so that the grain runs up and down, then most of the expansion would be left and right and forward and backwards (in and out), but almost no expansion up and down with the grain.
> 
> ...


Sorry George...I didn't realize I wasn't going to be able to read either......When I went to remove the extra words not related to my post it took away the gray shadow box so I attempted a quick color change without having time to review and change. Sorry for the confusion.

Tool agnostic.....pretty close ....let's clear it on up though.....You're on track with movement BUT which direction needs addressing... .the cracking is actually from the contraction/shrinkage (loss of moisture) as both outer edges are holding from the glued breadboard and the crack is the weakest point in the "link" in the shrinkage. USUALLY in the swelling/expanding (gaining of moisture) will result in a cup or a bow BUT that all depends on how other parts are fastened.

This is a quick reference.... it is complicated BUT learnable. Have a good day.


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## Steve Neul (Sep 2, 2011)

Jay C. White Cloud said:


> Hey Aaron,
> 
> Just ran across this over coffee this morning...
> 
> ...


It's true that antique tables were not built with steel bracing, largely do to the fact that steel used to be expensive. Steel today is nearly as cheap as wood and to incorporate steel in the onset of construction very likely would eliminate what sag the table would experience. Then the tables of that type are generally not built to that length. I think some additional help is called for.


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## Tennessee Tim (Dec 15, 2010)

Aaron...I do my pedestal slightly differ when figuring....BUT customer is "always" right....IF I get my choice AND this has factors in itself is I start out somewhere about 1/2 table distance then start adjusting from there....These are the 2 (in most cases) pressure points of support.....in your case = 5' or 2'6" overhang each way which isn't ideal....Id make the over hanging ends approx 18" to 2' which leaves a 6' to 7' span. ....6' isn't bad for 1 1/2" solid top with 2' overhanging counter balance....that's where the trick is...getting a counter balance to help reduce the sag span......This also gives you a comfortable seating at each end.

ONLY IF the customer is satisfied!!!


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## woodnthings (Jan 24, 2009)

*I think you followed this ....*



woodnthings said:


> I am suggesting a center support like a spine, running down the exact center of your top and attached from below. Because wood moves across it's width, any supports including breadboard ends will have to allow for that movement, either by elongated holes in the wood OR by Z clips in slots in the case of aprons. Breadboard ends will need additional space on either side of the tenons to allow for movement, about 1/16".
> 
> By using a support in the exact center, there is no movement issue.
> The center spine under the top could match in size and length the lower support on the trestles. Do NOT use a center trestle, it's not needed.


You're getting a whole bunch of differing responses. I am going strictly by the physics involved here and the visual appearance of additional bracing which IF visible, will detract from the design. Personally, I would never add steel bracing to an all wood table. If the support base was welded steel then that's a different design from the git go, so steel is part of the design. They didn't use steel 100 years ago... just sayin'

The physics are simple in this case, an unsupported load will sag over time. If you support the load in this case, which is the free weight of the slab itself, in from the end as you have in your trestle design, then the span decreases and so does the amount of "sag". As Tim suggested, there is a balance point where the cantilevered ends and the span sorta reach equilibrium and all is well. If however, you can't move the trestles in for reasons known only to the client, then you can add a spine as I suggested which would only be visible by leaning over and looking under it. The spine will prevent sagging because it's a vertical member not a horizontal member and when it is attached it will stiffen the entire top. Because it is centered there is no concern about wood movement. The wood can expand or contract on either side of the spine with any effect. 

The top is now supported by an "H" platform rather than just 2 cross pieces, the trestles. It can't twist or sag now. It's a simple solution and I can't really say I've ever seen it done before, so this is sorta new territory. BUT I would be willing to bet a case of draft on the "won't sag side" of the equation, however..... :wink:


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## Rebelwork (Jan 15, 2012)

It will sag in time without support. You can run one beam down the center but you will need a brace in the center..

Yes..the customer is always right, As long as they understand and sign the agreement...


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## 35015 (Nov 24, 2012)

Part of the reason it can getting frustrating on forums is sorting out those that have opinions about how things ought to be done and those that have actually done it more than one or twice...So I do apologize in advance for being rather blunt with this response...



Rebelwork said:


> It will sag in time without support. You can run one beam down the center but you will need a brace in the center...


It can sag...yes, but only if it is not designed properly with appropriately sized framing members to the table...including the table top. 

Not all historic examples of this style of table have supports, as many do not have any support at all other than Leg Truss work near there ends, appropriate thickness of planking and bread-boarding with perhaps some additional cross grain sliding keys for some wood species to address potential seasonal warp. Yet this is only found in some forms... That is not an opinion...that is direct observation of how many had been made, or I have built. They did not sag to any applicable amount over the centuries of use, nor have I had any of mine have issues.

To illustrate that further and not to belabor the point with engineering formula, span charts and related...a structural plank floors or roof deck (on averages here only) with a 2" splined deck can typically span over 8' without and support in between of any kind other than beams at 8' centers. I've been part of projects where they span 16' with only slightly thicker decking. Properly built Harvest or Farmer Tables can do the same thing with certain traditional designs. Case in point, our current project flooring (2" splined decking) is spanning over 5' between primary framing timbers...Simply put, there isn't a single joist in the entire structure...and that is a floor carry a significant live load. The timber frame workshop I work in has joist that are on 4' centers with loose plank just laid and not jointed...

Some Harvest Tables do have support...many do not and work just fine...


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## enzobindo (Jan 2, 2018)

Lots of great help on this topic, and thank you AaronWW and Toolagnostic for your responses to my post.


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