Relative rigidity of material for shelves?

[Mike W W]

Say you had three boards cut to form shelves: one each of the following materials:

1) MDF 2) Plywood (the rough stuff sold at B&Q) 3) Pine

Which will be the least prone to sagging when weight is applied?

Thank you,

Mike W

[Mike W W]

PS, All three boards being the same size and thickness of course. Mike W

[The Medway Handyman]

Check out The Sagulator

[Guy King]

The message from Mike W W contains these words:

Assuming the pine has its grain along the shelf then that'll be most stiff. The ply next, then the MDF.

However, in real applications shelves are often supported with a batten at the back edge, and that would make ply probably the best bet as it's cheaper.

MDF can work very well, I've got 2' wide shelves beside me some heavily loaded (paperbacks all across and three layers deep) and they're not sagging. They're held up at the ends with shelf wires in slots.

[The Medway Handyman]

According to The Sagulator I mentioned earlier the least prone is the pine, then the ply, then the MDF

Calculation for a 1000mm long x 300mm wide x 18mm thick shelf with a 20 kg load give the pine & ply sagging by around 2mm with the MDF at 7mm!

[Guy King]

The message from "The Medway Handyman" contains these words:

MDF also creeps over time far more than the other two.

[Stuart Noble]

Pineboard (laminated pine) is your man. Same strength but no movement. Most merchants stock it in a variety of widths

[Mike W W]

Thanks for confirming that. It's exactly what I ended up buying - and it was surprisingly inexpensive too. £8.75 per 7ft x 2ft sheet (from 'In Excess').

Thanks to all respondees.

Mike W