View Full Version : MDF Span For Desk Top
Lonnie Gallaher
03-08-2024, 11:15 PM
I am building an office desk that will be 8 feet long. It will have 3 legs. One at each end and one at the center. The end legs are 2 inches thick built-up plywood with a 4 inch extention forming an ell that will be bolted with 1/4 furniture bolts into steel inserts in the top. The center leg is 2 inches thick with 3 inch extensions at each side forming a tee. The connection is the same as the ends. This will provide 2 equal spans of about 38 inches.
I will be using 3/4 MDF for the top. I orginally planned to laminate a perimeter frame about 6 inches wide to make the top 1 1/2 inch thick. The top will be banded with 3/4 x 2 maple. Any thoughts on if the top will stay flat or should I laminate a solid 1 1/2 MDF thick top? Or something else?
Thanks for your help.
Jerome Stanek
03-09-2024, 8:18 AM
When we installed desktops for CVS we would use 3/4 MDF and span 32"
Bruce Wrenn
03-09-2024, 8:40 AM
A couple of old bed rails screwed to the bottom will solve sagging problems. Screw about every six inches along their length.
Maurice Mcmurry
03-09-2024, 8:52 AM
That is large for a structure without a skirt. For a span of 38 inches I would go with the 6 inch wide perimeter frame and a 1x4 or 1x6 center build down too. I would use strong solid wood for the build down. MDF feels strong but has a tendency to sag over time, even at 1 1/2" thick. I always want any non portable table or desk to be able to withstand someone standing in it, which has me thinking about a 4th leg as well.
Lonnie Gallaher
03-11-2024, 10:47 AM
Thank you for all of you suggestions.
Maurice Mcmurry
03-11-2024, 11:05 AM
This interactive tool gets a mention here at SMC several times a year. It is very helpful.
https://woodbin.com/calcs/sagulator/
Michael Burnside
03-11-2024, 1:49 PM
Personally I would reinforce with a 1x1 steel square tubing and hide with a skirt.
John TenEyck
03-12-2024, 3:34 PM
If you have knee clearance for a 3 or 4" high stretcher at mid depth of the top I would add it. Stretchers offer a lot more bending resistance than perimeter frames (by the square of the height), though they too do help.
John
Howard Rosenberg
03-12-2024, 6:32 PM
MDF can't support its own weight (it has no grain).
Add a lip to all four edges to create beam strength. Or build a torsion box.
I've built bookcase with eight-foot spans supported inside house joints (dadoes) in the bookcase gables.
Books are heavy. Hundreds of books even more so.
Zero sag.
Works every time - just find good instructions on building a FLAT torsion box.
Or - if you just add a lip around the edges, you'll be fine too.
Chris Parks
03-12-2024, 8:13 PM
Build a torsion box using 6mm skins and 3mm internal ribbing and it will never sag and won't need a crane to lift it.
Richard Daugird
03-20-2024, 4:34 PM
One more vote for torsion box.
Justin Rapp
03-22-2024, 9:35 AM
I built my son's desk from MDF on top and Poplar for the base. The MDF spans the inside area of the apron is 21.5 x 34.5.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.