Longest Unsupported Span For 1.5" MDF Benchtop?

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Forum topic by HorizontalMike posted 06-08-2010 11:27 PM 4595 views 0 times favorited 7 replies Add to Favorites Watch
View HorizontalMike's profile


7063 posts in 2331 days

06-08-2010 11:27 PM

I am in planning stages for building a new bench and wonder just how long a span would be practical for a 3/4”x2 thick MDF bench top? I am planning on having at least one mobile planer cart rolled/stored under the bench top. Bench will be free standing (not able to attach to structural wall).

-- HorizontalMike -- "Woodpeckers understand..."

7 replies so far

View rhett's profile


734 posts in 3085 days

#1 posted 06-08-2010 11:43 PM

Mdf has little structural integrity. As a rule of thumb any material is 2x stronger when stacked, the strength increases to 8x if the two are glued together. For maximum strength you might imbed some 1” square steel tube in the middle.

-- Doubt kills more dreams than failure.

View Nomad62's profile


726 posts in 2376 days

#2 posted 06-09-2010 12:41 AM

MDF just loves to hang down between supports, not so much right away but over a year or two’s time. I wouldn’t go more than 6”. It also absorbs moisture and swells accordingly. Highly recommend plywood over MDF, even 2×6’s laid flat as a bench top would be better.

-- Power tools put us ahead of the monkeys

View a1Jim's profile


115167 posts in 2994 days

#3 posted 06-09-2010 12:52 AM

I think 16” oc is fine

-- Custom furniture

View Pete_Jud's profile


424 posts in 3170 days

#4 posted 06-09-2010 01:06 AM

I built my 4×8 out feed / assembly table with the 2×3/4 mdf top supported with 2×4’s on 16 OC. It has not sagged and is still perfectly flat. The 2×4 frame is supported on 4×4 4 ft OC.

-- Life is to short to own an ugly boat.

View HorizontalMike's profile


7063 posts in 2331 days

#5 posted 06-09-2010 01:59 AM

I currently have an old (~40yr) bench that I was given that has served me well but is on its last legs. It was “nailed” together and has 2×4 legs that are now coming apart like balsa. What I originally liked about this bench was the top that has flat 2×4s topped with 1/2” ply with a 2×4 frame under that.

That being said, I have been thinking about using a couple of the unfinished particleboard Base Cabinets from HD. Building such a bench top on these things would make the top very high (nearly 40”) and I don’t like the idea of particleboard sitting on concrete that gets damp on occasion.

And now Pete’s massive table on casters has my attention, I am going to have to reconsider my options. Wow. My current needs will probably mean building something closer to Pete’s router table setup, but incorporating my miter saw with an extended fence.

Decisions, decisions… Sure like the information and ideas I am getting here on LJ. Thanks guys.

-- HorizontalMike -- "Woodpeckers understand..."

View John Ormsby's profile

John Ormsby

1283 posts in 3154 days

#6 posted 06-09-2010 06:10 AM

Why not build a very strong torsion box out of MDF? You can make it thicker but lighter and stronger. It will not sag.

-- Oldworld, Fair Oaks, Ca

View Dragonsrite's profile


136 posts in 2814 days

#7 posted 06-09-2010 06:23 AM

When I decided that I wanted to span ~10’ and still be able to drop a V8 in the middle, I went with 22 2×4s on edge bolted together every 24” with 1/2” threaded rod. It all sits on a pair of 4×4 leg assemblies with zero center supports. I used a router & sled setup to flatten it and it’s been doing great for almost 20 years now.

Cheap, fairly easy and ummmm, a wee bit heavy :-)

-- Dragonsrite, Minnesota

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