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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".

maple countertop

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 72x24 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?

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    If this is solid maple (as opposed to particle board with a maple veneer), then you could park a truck on it and not have it sag. – Aloysius Defenestrate Apr 2 at 16:40
  • @AloysiusDefenestrate Are you thinking of a table supported from all four edges? I intend to add leg support at just the four corners, and given its span (72") I myself would not want to sit on it with my 170lbs. The table itself is reportedly 85lbs (!). – Sam Apr 2 at 16:55
  • Yes, I'm thinking about something with 4 legs at the corners. The weak link in the equation really is the legs and how well they attach to the top. – Aloysius Defenestrate Apr 2 at 17:00
  • Is the maple top a butcher block counter top ? – Alaska Man Apr 2 at 17:04
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    @Sam The photo you posted IS butcher block. As Aloysius said, those are extremely strong because of the maple and the orientation of the grain. Legs at the corners will be sufficient ( for sag ) because it is strong enough but You need to have cross bracing to prevent racking. That would be another question. – Alaska Man Apr 2 at 17:13
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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.

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    You're not wrong, but given the materials in question, I think you've overgeneralized. The sagulator tells me that 500 pounds total on the worst maple will deflect it one millimeter total. – Aloysius Defenestrate Apr 2 at 18:04
  • thanks for your opinion? – Ack Apr 2 at 18:11
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There is a cool website that calculates sag based on a variety of inputs. https://www.woodbin.com/calcs/sagulator/

It also naturally depends upon where you attach the legs. If they were set in from the ends a fair bit, that would go a long way in preventing sag.

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  • Thanks for the link. Will check. About the leg placement. I omitted to mention. I'm pretty sure that a leg right smack in the center of the table would remove any worries, but the luxury of a lot of leg room would also be all but gone. So, yes, I intend for the legs to go as near the corners as possible. (24" is already too narrow; and so the stability of the table would be bad if I got too ambitious and moved them closer to the center on the short sides.) – Sam Apr 2 at 16:50
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    Hi Sam: I didn't mean to suggest you move them in from the sides, that wouldn't help much and you are right it would make the table unstable. What I was suggesting is to move them inward from the ENDS. Even 8" would help by narrowing the distance from 72" to 56". That would still give you plenty of leg room/chair room, IMHO. – George Anderson Apr 2 at 17:43
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    One more thought! You could angle the legs out from the table top. That would add stability. You'd want to use use some sort of cleat where the legs would attach to (maybe via a mortise / tennon) and the cleat attached to the table . That or there are mechanical means of attachment that are easier to use (but not as pure woodworking! LOL) : Here is a link to ways to attach table legs: tablelegs.com/resources-how-tos/… – George Anderson Apr 2 at 18:13
  • The biggest problem by far is avoiding the torque placed on the legs at the mount point when you ever try to move, or lean against, the tabletop. That's why legs are often braced against "joists". If you can get legs which screw into the top at three points, well separated, that is a good choice as well. – Carl Witthoft Apr 2 at 18:56
  • @GeorgeAnderson Great idea, though now it sounds I need to be a carpenter to tackle this level of work! Even if I get comfortable fitting an 85-lb table on angled legs, it would be quite tricky (for me) to cut the bottom ends at the appropriate angles. I would find uncut legs ghastly with the round black rubber feet, and almost as ghastly putting all their stress on a single point, destroying carpet and hardwood alike. – Sam Apr 2 at 18:57

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