# Help with building 10' desk without legs or floor support



## robble (Nov 7, 2011)

Aloha from Hawaii! 

I have a room that is 10' wide and I want to build a "desk" or "wide shelf" the entire length of one wall without legs or big L brackets. My plan is to screw 2x4s into the studs at the height of the desk along 3 walls. These 2x4s are to be the support for (2) 2"x10"x10' redwood planks. I am sure 2x4s will support the plank against the back wall very well but my issue is with the 2nd plank that would only be supported by the 2x4's on each end. 

I was thinking of using three to five 1/4" thick by 1" wide by ~8" long steel bars with a few holes to screw into the underside of both planks along the joint of the planks. I'm thinking the plank next to the wall which is supported along it's entire length with the 2x4 along the wall could keep the 2nd plank from sagging over time via the steel bars supporting the second plank.

Is this idea feasible? My end goal is to have a ~20" wide desk/shelf that is 10' long without any supports going to the floor. It won't be holding significant weight for long periods of time - a couple computer monitors and several books (all of which would be on the plank closest to the wall). On rare occasions I might need to stand on it so I'd like it to be able to hold transient weights of ~160lbs. 

Whatever solution I use must pass the wife acceptance test.

I remember from wood working class 20 years ago on how to join two boards together using dowels and glue but I don't have a jig or clamps and doubt I could drill the holes perfectly enough.

I hope I've worded this clearly enough for everyone to understand what I am talking about.

Mahalo!

Robert


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## robble (Nov 7, 2011)

I guess either everyone thinks i'm crazy and is to polite to tell me or no one has good idea for me :whistling2:

I decided to go ahead and join the boards "right" instead of rigging the steel bars.

Now my plan is to use a whole lot of dowels. After researching a ton on dowel jigs I decided the only one that i can be sure of accuracy without emptying my life's savings is dowelmax. At 309 it'll only break my checking account. As expensive as the wood was it is insurance I won't screw it up.


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## woodnthings (Jan 24, 2009)

*Can you glue?*

If you can "properly" glue the 2 planks edge to edge that will be sufficient...JMO.
Edges must be square and straight, not rough sawn or twisted or curved.

If not, there will have to be a mechanical fastner of sorts, dowels, cross bolts, long through rods.....14" lag bolts from the front into a counter bore.... 
So it depends.  bill
cross bolts:
http://www.rockler.com/product.cfm?page=30249&filter=bed bolts


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## cabinetman (Jul 5, 2007)

You can just edge glue and clamp the boards if the edges mate well. For a 10' length, I'm betting you will get sag...especially if you want to stand on it. The wall cleat (which doesn't have to be a 2x4) will take care of the back, but for the front I would suggest a pretty hefty angle iron...1/4" x 2"...maybe two of them.












 







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## yocalif (Nov 11, 2010)

I think you can adapt this idea for something attractive that would match your table top and give you the necessary support.


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## robble (Nov 7, 2011)

Thanks for the last two ideas. I really like the angle iron one as it would be very simple and I could have it far enough from the edge so it wouldn't be visible without crawling under the desk. I could cut a simple L notch into the end support boards and drop it in.

The next one looks like a great idea also but for my purpose I don't want any type of leg going down where it would be visible.


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## yocalif (Nov 11, 2010)

No Problem...
I think though that you can make the down strut about 12"-14" stain it the color of your desk top, and make it look like part of the furniture with rounded edges. Also a rounded cap on the end so the 3 pieces are not shown.


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## woodnthings (Jan 24, 2009)

*If it were me ..*

I'd just properly glue the planks together and place them "crown side up" if there is one and then see what happens.
If needed the angle iron brace underneath need not run all the way into the side supports for strength. they can stop 4-6" in from the end, because in that short amount it won't sag no way, no how if...it's gonna sag at all....crown side up and all.
Don't forget that rooms often do not have square corners and make a pattern for each corner to see if they are at an angle or if drywall mud has made the wall measurement less than the same 24" from the back wall. Templates are good. :thumbsup: Then allow 1/4" less in length for the planks to drop into place.  bill

BTW a more sophisticated approach would be a truss rod like guitars have with a tension rod to tighten up.


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## aardvark (Sep 29, 2011)

Architectural standards for a beam of that length holding floor weight is not so big. 10ft long and only 20" deep, work out to a uniform loading of 50lbs per running foot (or standard floor loading) doesn't take a big beam. 2, 2"x 6" pine boards with a plywood flitch is adequate to hold (as a guess, w/o pulling out the books) 35 to 40 lbs per lineal foot. In 10 ft that would be ~250 to 350 lbs total that the shelf will hold without ANY deflection (or L/360 deflection, which is very minimal...L/480 can be used and is more rigid yet. Those are the standards. L/240 is unacceptable, and deflects too much) 

Now if 2" x 6" is to tall, you can go to 2" x 4" , using 3 total and plywood between each 2x. You are getting thicker, but less tall. All plywood I'm speaking of is 1/2" cdx. 
These can be rested on 2"x6" blockings between the studs on each side.

Next step is engineered lumber like glu-lams, micro-lams, para-lams that lessen the sizing but no matter how you do it, these products only come in nominal 2" x 4" inch sizes, at a minimum. So you are stuck at a 3 1/2" total height, minimum.

Ask any lumberyard counter person to just size a beam for you to hold 300 to 400lbs "total load " with the height you can live with. They can come up with an option straight out of the books/computer.

I can dig the books out on manufacturered wood beams if you would like as can any lumberyard counterperson.


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## woodnthings (Jan 24, 2009)

*what that got to do with this?*

I have a room that is 10' wide and I want to build a "desk" or "wide shelf" the entire length of one wall without legs or big L brackets. My plan is to screw 2x4s into the studs at the height of the desk along 3 walls. These 2x4s are to be the support for *(2) 2"x10"x10' *redwood planks. I am sure 2x4s will support the plank against the back wall very well but my issue is with the 2nd plank that would only be supported by the 2x4's on each end. 

There are no "beams" in this design, except the 2" x10" planks which act as very shallow "beams", 2" deep. 
I'm not understanding all your other references...?
Can you please explain your theory? :blink: bill


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## cabinetman (Jul 5, 2007)

woodnthings said:


> I have a room that is 10' wide and I want to build a "desk" or "wide shelf" the entire length of one wall without legs or big L brackets. My plan is to screw 2x4s into the studs at the height of the desk along 3 walls. These 2x4s are to be the support for *(2) 2"x10"x10' *redwood planks. I am sure 2x4s will support the plank against the back wall very well but my issue is with the 2nd plank that would only be supported by the 2x4's on each end.
> 
> There are no "beams" in this design, except the 2" x10" planks which act as very shallow "beams", 2" deep.
> I'm not understanding all your other references...?
> Can you please explain your theory? :blink: bill


I may be wrong, but my understanding of "beams" (wood), is when used on edge for support or strength, such as rafters or joists. A 2" thick plank used flat would be useless as a "shallow beam". 

*"BTW a more sophisticated approach would be a truss rod like guitars have with a tension rod to tighten up."*

I'm trying to envision how that would work at all.












 







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## aardvark (Sep 29, 2011)

Yup laying flat at less than 3 1/2" w/ a few layers (like I described) don't get it.
Span is too great.
Otherwise you gotta break the span (say) midpoint of the 10ft.

3 ea, 1 3/4" x 3 1/2" microlams , glued and nailed , or 3, 2" x 4" (nominal) with 2, 1/2" ply layers glued and nailed. Both options will hold well, but not quite to floor loading (50lbs per sq ft).

Another option is 2" x 4" beam with a steel 1/4" plate sandwiched and bolted w/ thru bolts.
I rarely spec steel in those scenario's and would have to dig in the books for loads.
The loads I'm giving are off the top of my head, and should be adequate.


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## woodnthings (Jan 24, 2009)

*you are not wrong...*

Quote from cabinetman:
I may be wrong, but my understanding of "beams" (wood), is when used on edge for support or strength, such as rafters or joists. A 2" thick plank used flat would be useless as a "shallow beam". 

regarding the "typical" use of wood beams. When I took the Strength of Materials classes when I was studying to become an architect, I learned that any cross section shape can be considered a "beam" whether it's a square, I, H, round, hollow square, hollow round as in pipe...etc. So whether you orient the wood horizontally or vertically it still has resistence to bending, it's just not typically used horizontally because it has the least resistance/strength that way, hence the use of the term "shallow" beam.  http://www.absoluteastronomy.com/topics/Beam_%28structure%29

A truss rod can be made using surface mounted brackets or let into the surface like a guitar neck. http://www.bigappleguitar.com/guitar-truss-rod-installation/ 

A truss rod in this application would be difficult to inlet, so I mentioned it as a "sophisticated" solution. JMO
Barn construction and timberframe buildings use a truss rod either above or below a beam which is heavily loaded to resist bending. It's performs essentially the same as an angle iron but tapered to a minimum at each end and is "adjustable" The full width of the angle is not need at the ends since the loads are usually distributed over the center span or concentrated at points in from the ends. Bridge design reflects this economy of use of material as they taper from the center to the ends.  bill


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## aardvark (Sep 29, 2011)

Woodnthings
Yes correct, and yet...
Simple wood beams don't matter if they are laid horiz or vert. It's the height that takes precedence. 
A 2"x 12" laid horiz will bend under it's own weight, as an example.


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## cabinetman (Jul 5, 2007)

aardvark said:


> Woodnthings
> Yes correct, and yet...
> Simple wood beams don't matter if they are laid horiz or vert. It's the height that takes precedence.
> A 2"x 12" laid horiz will bend under it's own weight, as an example.


+1.:yes: I agree. I had to read posts again as when they are edited and information gets changed, added, or deleted, you'd never know unless the post is read over again.

As posted: Quote from cabinetman:
I may be wrong, but my understanding of "beams" (wood), is when used *on edge* for support or strength, such as rafters or joists. A 2" thick plank used flat would be useless as a "shallow beam". 

I think this was what was added to the post if I remember correctly. Hard to remember what was in a post after it's been edited. I used the term "on edge", which to me would indicate there was a difference (width and thickness) in the dimensions. Sometimes the terminology doesn't quite cover all the intended meanings.












 







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## woodnthings (Jan 24, 2009)

*there are no beams here, just planks*

Original Post:
I have a room that is 10' wide and I want to build a "desk" or "wide 
shelf" the entire length of one wall without legs or big L brackets. My plan is to screw 2x4s into the studs at the height of the desk along 3 walls. These 2x4s are to be the support for *(2) 2"x10"x10' redwood planks.* I am sure 2x4s will support the plank against the back wall very well but my issue is with the 2nd plank that would only be supported by the 2x4's on each end. 

I said:
There are no "beams" in this design, except the 2" x10" planks which act as very shallow "beams", 2" deep. 
I'm not understanding all your other references...?
Can you please explain your theory? :blink: 



aardvark said:


> Yup laying flat at less than 3 1/2" w/ a few layers (like I described) don't get it.
> Span is too great.
> Otherwise you gotta break the span (say) midpoint of the 10ft.
> 
> ...



Like I said what's all the discussion of steel plates, floor loading, micro lams got to do with the 2 - 2X10" redwood planks? 
The OP did not mention "standing" on the planks, AFAIK. 
I recommended a "proper' glue joint, no dowels and see what happens. If possible put the crown side up as a pre-stressed approach. If it sags, then it can be reinforced at a later date. A piece of angle across the very front edge, "L" shape up would not show underneath and could be capped with a trim piece in redwood, or painted black and left visible. Buy gluing the 2 slabs together any "sag" will have to be across the entire 20" which the back brace is restricting, so it presents an rather complicated stress analysis out to the front edge.... way beyond my capablity. It will also be helpful to place any heavier loads on the extreme ends if indeed there will be any, to avoid sag at the center. JMO.


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## cabinetman (Jul 5, 2007)

woodnthings said:


> The OP did not mention "standing" on the planks, AFAIK.





robble said:


> On rare occasions I might need to stand on it so I'd like it to be able to hold transient weights of ~160lbs.
> Robert


 









 





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## woodnthings (Jan 24, 2009)

*I stand corrected*

:blink:
If that's the case "rarely"...I'd just keep a prop post handy and wedge in the center for those rare occasions.


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