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5 Foot Countertop Span

EricBrewer's picture

Hello,


I am getting a 24inch deep, 7.5 foot desktop with 15inch wide base cabinets under each end.  This leaves an unsupported span of 5 feet.  I plan on using a plastic laminate or hardwood laminate top (made with particleboard under the top surface and a hardwood edge in front) and supporting the entire back of the desktop with a 2x4 screwed to the wall.  The dealer says this will be fine, but she isn't very convincing.  Do you think the front of the desktop will sag over a long time.


Also, the desktop will have two 30inch kraftmaid drawer units screwed to the bottom.


Thanks, Eric

(post #75583, reply #1 of 21)

Eric,


My guess is that it would sag over time.


If the counter was built up particle board, say double 5/8" at the edges, you might consider attaching a piece of angle iron to the underside of top layer and hiding it from view behind the front edge "build-up" strip.


Can get some surprising stiffness from a seemingly small piece ( 3/4 x 3/4 x 1/8). Bore some holes and screw it to the underside, appropriate adhesive would also help.


Jim


Never underestimate the value of a sharp pencil or good light.  

Never underestimate the value of a sharp pencil or good light.

(post #75583, reply #2 of 21)

It could be that a proper attachment of the two drawer units he mentions creates a de facto torsion box. If the end units and the drawer units are solidly attached to each other and the top, sag would probably not happen.

(post #75583, reply #4 of 21)

unfortunately, the drawer units attach to the underside of the desktop, not the side-cabinets at all.


Eric

(post #75583, reply #5 of 21)

Could they attach? Two 30" units filling a 5' span. Unless I'm picturing this wrong, all of the cabinets touch each other, so a T-nut or other connector _could_ attach them. Yes? No?

(post #75583, reply #6 of 21)

The saleswoman said that the drawer units attach to the top, but it seems that they could attach to the sides as well.  


I am trying not to insult her by asking too much, since she said that a 5 foot span was fine as long as it is supported in the back.


Eric

(post #75583, reply #9 of 21)

Once the unit's installed, pull the drawers, drill one hole toward the bottom front and bottom rear where the drawers touch each other and the end cabinets. That's six holes total. Insert a T-nut in each. It's an essentially invisible solution, it'll take all of 5 minutes and only require a drill and a screwdriver, and it'll take away any worries.

(post #75583, reply #7 of 21)

Just from looking at some of the laminate countertops in my house, it seams that a piece of angle iron could easily be added along the underside of the front edge.


Thanks, Eric

(post #75583, reply #3 of 21)

Will the hardwood edge in front be thick enough that you can add soemthing underneath but still keep it concealed?

If it is, you may be able to put a 2X4 laid flat under the front edge, or maybe partway back to add some support.

If quizzes are quizzical, what are tests?

(post #75583, reply #8 of 21)

Wow, talk about right up my alley.

We make desks with up to a 78" span, supported at the ends and by a back panel, at up to 30" deep, and we warranty them for 12 years. Our laminate tops for these are 1 1/8" flakecore particle board core with the laminate on the top surface and a phenolic backer on the bottom surface. We have all manner of edge treatment, but most of them are non-structural.

If you can't get (or don't want to have to carry around) 1 1/8" PB, lay up 3/4 and 1/2, and put laminate on both the top and bottom surface. You'll be fine. We make kajillions of these things.

did

(post #75583, reply #10 of 21)

No way I'd do it the way she's suggesting unless I was putting my feather collection on it...even then I think gravity would extract its toll in the long haul.


 At the very least double thick top, glued and screwed/stapled. If you did it this way you could incorporate steel into the span and bury it in the bottom layer. Think 3/4 x 3/4 grooves (assuming 1 1/2" total thickness) running parralel to the span, strips of ply forming the grooves. PL premium and countersunk screws on the steel and run full length over base cabs.


The acid test for me would be "can I sit on it without sagging"? Somebody might someday :)


 


PJ


Everything will be okay in the end.  If it's not okay, it's not the end. 

 

Everything will be okay in the end.  If it's not okay, it's not the end. 

(post #75583, reply #11 of 21)

Do you guys think it might be easier to just use a different material for the top, such as a smooth, solid wood slab, like a door or butcher block?  Could those span the 5 ft better?


Thanks for all the help you've all given so far.


Eric

(post #75583, reply #12 of 21)

Butcher block might do it...if it were thick enough...maybe 2 1/2 - 3". Visually, it'd be pretty imposing, I imagine. And weighty, too.

PJ


Everything will be okay in the end.  If it's not okay, it's not the end. 

 

Everything will be okay in the end.  If it's not okay, it's not the end. 

(post #75583, reply #13 of 21)

I used to have a plan review desktop that was a 2'6" wide and 8' long piece of 3/4 cabinet grade birch. the desk was eventually used for more than light weight plan review and held a desktop monitor, phones, printer, etc.  


I ripped a strip of the 3/4" birch 1 1/2" wide and glued / fastened it flat under the top flush on all edges/ I then faced the 3/4 top and 3/4 rip strip (1 1/2" total) on all edges with a piece of hardwood 1 5/8" x 3'4" glued and fastened.


The top was supported on each end by a 2 drawer file cabinet, so the clear span was about 5'. The top worked for about 5 years with no sag. We just moved into our shop to cut up and use for shelving. It is still straight.  


 


Edited 1/5/2007 2:08 pm ET by txlandlord


Edited 1/5/2007 2:11 pm ET by txlandlord

(post #75583, reply #14 of 21)

Eric


Re-read this post!


83724.9


Its all you need to know. I've done what Did has done and seen it done that way for all the years I've been doing this stuff. It will work.


The key to that whole process is the backing on the underside of the counter top, thats the one thing most people will skip to, matter of fact I dont think I have ever seen a counter top place put the backing on the underside.


If you dont want to get the 1 1/8 particle board, and after you lift it you'll know why you didnt want to get it,  you can always glue two 3/4" pieces together with the solid wood across the front edge. Of course that will be heavier then the 1 1/8" stuff when done!


Doug

(post #75583, reply #15 of 21)

Yeah, that 1 1/8 stuff is pretty beefy!

The laminate on the lower surface adds a remarkable amount of strength. We suspend filing peds underneath our 78" desktops without issues (in our case, "issues" basically means it deflects less than what would cause a pencil to roll freely on the desk).

did

(post #75583, reply #16 of 21)

Did,

Are you bonding your bottom laminate with contact cement? What kind? It seems to me that this would be very strong for transient loads, but that the glueline could creep, thus allowing the counter to sag under a prolonged dead load.

I'm not doubting that your stuff works, just wanting to have a better feel for the dynamics behind the success. Thanks.

Bill

(post #75583, reply #19 of 21)

I'm not sure what the adhesive actually is - this is an industrial process, it's done in a press. I'll ask on Monday. We do creep tests (well, we call them "permanent set after loading" I guess) and stuff that doesn't pass that doesn't get sold.

did

(post #75583, reply #17 of 21)

I have always used a slab door for the top in your case.

(post #75583, reply #18 of 21)

Your proposal didn't bother me until I got tyo the drawers underit pat. So it depends how these mount and what you will be putting in them. Gold and lead are too heavy. Recreational activity with the blonde secretary is too much, BUt just a few pencils and staplers should be fine.

I have an adjacent thought too though. Base cabineets are 34.5" tall and with the counter, you have a top that is 36" off the floor.
Typical desk sets are more like 28" to 30", so your top will not be comfortable to use, unless you have specially considered this in your plans.

 

 


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(post #75583, reply #20 of 21)

Sorry I did not mention that the only things on the desk will be keyboard, phone, pencils, papers, elbows, mouse... and also that the cabinets are designed for office: 29 inches high.  Thanks for checking, though.


Eric

(post #75583, reply #21 of 21)

I built a desk with a similar span (and KraftMaid drawers even). I made brackets to support out of wood ordered to match the cabinets.

I've also made a torsion box desktop with no visible support (on hidden cleats).

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