My current working desk is a 1" thick table.
Even though there is not much weight on top of the desk (screen, keyboard, laptop ), the table's own weight, given its top dimensions, 60" x 30" ( 150cm x 75cm ) means that an underframe is necessary. Simply attaching four legs will mean that it will start to sag after a year or two. ( This is right; isn't it? )
I fitted it with a Bekant underframe from Ikea. I lowered the Bekant to its lowest height and am not using a keyboard tray.
It's not quite right. My knees will sometimes bang on the underframe.
I see on the market a table that's 72" x 24". This one is made from maple ( the first is birch ). But the thickness is 1 3/4".
Sure, a 72" x 24" would be unusual for a desk. It's meant for a countertop. Still:
Can I fit four legs, and just four legs, on a 72×24 maple table and expect it not to sag?
Or is this a recipe for me to have a nice table for two years, and then inevitably see it getting worse and worse, until it's quite bad after five years?
Best Answer
Will it sag?
Yes. Everything 'sags', there is no rigid material
A more on point question is then how much will it sag? Or, even more on point, will it sag more that I am ok with?
How much is sags is dependent on the dimensions of the material, physical properties of the material, at distance between the supports and the weight applied to it. For a given weight and material, the two things that have the most affect are the thickness of the material and the distance between the supports. Since you know the distance between the supports, then it's all about the depth of the material. Go deep or go home. Thicker = less sag.
The second part is entirely subjective and is in your mind not ours. It is not possible for me or anyone else to answer that question.
Will is sag more over time?
This is called creep. Wood can creep. It will creep 'very little' to 'some'. Particle board will creep a 'lot' as you may have witnessed yourself.
Will it creep so much as to bother you? Probably not unless you are at the end of your sag comfort zone because this means that the wood is both likely stressed enough that it will creep more and that any more sag than is already there would put you over the line on your comfort zone.
What to do about sag after it happens / or how to address it without making the entire desk thicker and not adding a middle support?
Use a bracing item under the desk. Thicken the desk in isolated areas instead of the entire desk. For example, add (2) 2x4s at about 1/4 in from the front or back. Or add a thicker edge banding. Or add steel angle iron.