MDF or Plywood

calver · Post by **calver** » Wed Apr 01, 2009 2:51 pm

I am planning to build a few book shelves and also storage cabinets.

Looking for suggestions. Is there several grades of MDF?

I remeber an unfortunate experience five years back with some material I bought at HD and the books were too much weight and cracked the material all the way through.

Dave C.

tdubnik · Post by **tdubnik** » Wed Apr 01, 2009 2:59 pm

If I were going to build shelves with either MDF or plywood, I would add a solid wood rabbeted edge on the front for the shelf to fit into. This not only makes it look better but adds strength and support for heavier loads.

tom_k/mo · Post by **tom_k/mo** » Wed Apr 01, 2009 3:02 pm

Dave, I made a bunch of shelves, almost like book cases for my kids to keep their toys on (didn't work, they still were all over the floor

) years ago, and they worked out well. I also have a whole wall of shelves I made in the basement for storage that I made with MDF and 2x4's. I've never had a problem with MDF shelves breaking, but you should either support them from the bottom (like I did with the basement storage shelves) or limit the width and span of the shelves and the weight of the items stored on them. I have seen unsupported (no bottom braces) shelves sag in the middle with heavy loads for an extended period of time. Just my own $0.02 worth of personal observation.

dusty · Post by **dusty** » Wed Apr 01, 2009 3:25 pm

calver wrote:I am planning to build a few book shelves and also storage cabinets.

Looking for suggestions. Is there several grades of MDF?

I remeber an unfortunate experience five years back with some material I bought at HD and the books were too much weight and cracked the material all the way through.

Dave C.

I don't know whether or not there are different grades of MDF but there are certainly sources of lesser quality MDF.

I strongly advise that you avoid MDF/plywood purchased from a borg. Buy materials that you want to last from a respectable lumber yard. You'll pay more up front but there will be a payback in the long run.

8iowa · Post by **8iowa** » Wed Apr 01, 2009 5:28 pm

Dave:

On page 28 of "Woodworking Wisdom", our own Nick Engler shows the following guideline for maximum spacing of 11 1/2" wide shelves;

3/4" particleboard..........24"
3/4" plywood................30"
3/4" softwood...............36"
1" softwood..................48"
3/4" hardwood...............48"

When this book was written, 1997, almost all sheet goods on the market met standards of the APA, the engineered wood association. Sadly, that is not the case today. The vast quantity of imported sheet goods do not meet APA standards.

I recently bought a 4' x 8' sheet of 3/4" birch plywood at Lowes. I selected the very best plywood in the store. When I got it home I was amazed at how thin the birch veneer was - sanding was out of the question. It's thickness measured .688 compared with .709 of an older piece of birch plywood.

Without digressing any further, I'm doing several shelving projects and I plan to use 3/4" white pine.

kd6vpe · Post by **kd6vpe** » Wed Apr 01, 2009 7:51 pm

I just finished a book shelf for my oldest daughter's book and stuff. I used 3/4 pine for the project. Dado'd the sides for the shelves and used brads and glue to hold the shelves in place. Pictures attached. Not alot of weight on them as you can see but they will hold alot. I also used brads though the back 1/4 plywood into the shelves for extra support. I am far from an expert just a hobbiest but they seem to be doing the job.

charlese · Post by **charlese** » Wed Apr 01, 2009 8:09 pm

Just a hobbyist that made up a real good looking shelf! Nice work, Dusty!:D It should serve for many years. Did you remember to sign it? It will get passed on and on...!:D

dusty · Post by **dusty** » Wed Apr 01, 2009 8:35 pm

charlese wrote:Just a hobbyist that made up a real good looking shelf! Nice work, Dusty!:D It should serve for many years. Did you remember to sign it? It will get passed on and on...!:D

Thank you very much, charlese BUT that is not mine. Mine doesn't look near that nice.

bobgroh · Post by **bobgroh** » Wed Apr 01, 2009 9:00 pm

Fine Woodworking magazine (March/April 2007 pg 38 on) had an excellent article on bookshelves which included a nice table showing shelf weight limits for different materials plus a nice summary of different ways to mount shelves. Nice article - you might be able to find it on the web.

The table shows the weight limits for 3/4", 1" thicknesses and 3/4" plus 2" edging. Materials (in decreasing strength) are red oak, poplar, eastern white pine, fir plywood and mdf. Weight limitations for 3/4" material and 30" length are (respectively)21 lbs, 17 lbs, 14 lbs, 13 lbs and 4 lbs. Woof. That's a big drop for MDF.

tdubnik · Post by **tdubnik** » Wed Apr 01, 2009 9:12 pm

bobgroh wrote:Fine Woodworking magazine (March/April 2007 pg 38 on) had an excellent article on bookshelves which included a nice table showing shelf weight limits for different materials plus a nice summary of different ways to mount shelves. Nice article - you might be able to find it on the web.

The table shows the weight limits for 3/4", 1" thicknesses and 3/4" plus 2" edging. Materials (in decreasing strength) are red oak, poplar, eastern white pine, fir plywood and mdf. Weight limitations for 3/4" material and 30" length are (respectively)21 lbs, 17 lbs, 14 lbs, 13 lbs and 4 lbs. Woof. That's a big drop for MDF.

MDF is a composite of short fiber wood products and a binder or glue to hold it togeter. It basically has very little strenght in and of itself. It works well for cabinet sides and backs that carry little weight or carry weight in a vertical direction. It CAN support horizontal weight IF it is reinforced with a LONG grain product (solid wood) along its long dimension. A solid wood front and back edge will greatly increase the load capacity.