Table Top Core - MDF or Baltic?

[Russ Filtz]

I've been planning to do a PC workdesk with solid wood edgebanding and a laminated top. Plans call for MDF cores to be used for all the laminated parts. I was thinking of substituting baltic birch for the MDF to make it less prone to sagging. Is this correct thinking, or does the ply have problems too? I believe the plans were calling for 3/4 or 1" MDF. The ply should end up a bit lighter to. Hate to think of moving a 1" sheet of MDF around!

[Ken Garlock]

Russ, I would go with the MDF. About 10 years ago I bought a corner computer desk from the local "Office supply Borg". It has 1 in. MDF with the standard Formica-type surface. During the time I have owned it, it has supported a 17" monitor, and now for the last 5 years, a nearly 50# 21" Viewsonic. I see no objectionable sag.

Just my experience, YMMV.

[Russ Filtz]

I was worried as the design is kind of a corner table setup and a pretty good expanse along the front middle seems unsupported. Can't remember if it had an apron, which would help. I think it didn't as it had a retractable keyboard tray thingy which I would do away with.

[Jamie Buxton]

I was worried as the design is kind of a corner table setup and a pretty good expanse along the front middle seems unsupported. Can't remember if it had an apron, which would help. I think it didn't as it had a retractable keyboard tray thingy which I would do away with.

MDF does have a reputation for sagging over time. Sometimes you see it in heavily loaded bookshelves. Plywood is less likely to do this (and it is much nicer stuff to work with). If you're going to put a 100-lb CRT-based monitor on this desk you might have an issue. However, LCDs are much lighter.

Be that as it may, a better way to combat sagging is to put a beam under the desk top. A piece of 2x4 on edge is much stiffer than a sheet of 3/4" MDF. In your design, the beam could run diagonally from the desk's left corner to its right rear corner. It will be under the monitor's weight, and it will be far enough back that you don't hit it with your knees.

If you want to put a drawer in your corner design, and you're concerned about the beam interfering with the drawer, there is a pretty good solution. You make the beam perhaps an inch taller than the drawer, and put a hole in it big enough to run the drawer through. That is, there is an inch-tall piece of the beam which runs underneath the drawer. This acts somewhat like a torsion box; to bend the desk top, the monitor has to stretch this piece of the beam, which is difficult.

[Bob_Hammond]

I just made a similar desk. It has a corner opening with cabinets on the right and left. I made mine out of 3/4 particle board, as that is what most of the pros seem to use. I added a second layer of particle board on the edges and the seams so that from the front, it looks like it is 1 1/2 thick. I edge banded the front with red oak, and then laminated the top. The back is supported by boards screwed into the walls.

So far, there is no sag. I even had my daughter stand on the open part.

Bob

[Gary Whitt]

I was thinking of substituting baltic birch for the MDF to make it less prone to sagging. Is this correct thinking, or does the ply have problems too? ... Hate to think of moving a 1" sheet of MDF around!
I won't use MDF at all. Period. :mad:
That stuff is bad for saw blades (ask Freud) and the dust is bad, too!!!
MDF is not that sturdy of a material, anyway.
Just look at checkout counters at stores...usually MDF (or pressboard) and laminate. Corners are usually broken off.

[Ken Garlock]

I was worried as the design is kind of a corner table setup and a pretty good expanse along the front middle seems unsupported. Can't remember if it had an apron, which would help. I think it didn't as it had a retractable keyboard tray thingy which I would do away with.

Russ, a quick rundown on the dimensions of my corner table:

2 sides against the wall are 48 inches.
2 sides at 90 deg. to each back side are 30 inches.
1 front edge 25.5 inches wide with a sliding keyboard tray under that edge.

Support is at three places:

back corner is two 4" pieces of MDF mounted at 90 deg. to each other to form a V-shaped leg.

sides: each is made of a sheet of MDF 18" deep and mounted on a flat piece 4 inches wide -- like a trestle table leg.

All supports are 3/4"

There is a 3/4" "modesty" panel 16" high between the rear corner leg and each side leg. This panel also is mounted on the legs such that it is in contact with the top, which I think gives added stiffness in two directions both from racking and top sag.

Moving it is a two man job, boys need not apply :(

Hope this helps :)

[John Shuk]

Does the apron help with sagging?

[Russ Filtz]

Any sort of apron will help structurally around it. Kind of the main reason they put aprons on tables I think, along with places to fix the legs. A large expanse in the middle would still be prone to sags even with an apron. My worry was that a large area on the "L" shaped table in front has no supports, just partial aprons on sides and none in the middle where the keyboard holder goes.