Do i use ply for 1m/sq shelf supported on 3 sides for 70kg+

[PingCrosby]

Hi

My question is basically - will 1/2" ply sheet have enough strength to support at least 70kg+ across a 1m/sq area when supported on only 3 sides?

Background ::

I have an old airing cupboard I am converting into a wardrobe. To keep things simple I intend to use an old Ikea wardrobe i have that fits nicely inside the space. (basically i throw away the doors and chop the height).

The airing cupboard is above a staircase; which runs through it, so I am unable to place the wardrobe on the floor.

To rest this wardrobe on I intend to screw 2x2 batons into the existing studs to give support along the left/right sides and back (back is brick). My plan was then to rest a ply 1/2" sheet on this. The span is approx 1m/sq.

 

[Deleted member 174758]

It depends on what you regard as an acceptable amount of sag. Very simple way to find out - feed the figures into The Sagulator. Working from your figures and assuming that the shelf was 1m x 1m, made from 12mm plywood fir with no edging strip and the load evenly distributed it came up with a figure of 8.13mm.
whilst a centre load gave a figure of 16.26mm. These figures are obviously way too high

If you add a front lipping 50mm deep inthe same material that the sag for centre load drops to a much more reasonable 1.61mm. Similarly a 2 x 2in (44 x 44mm) pine batten as front lipping will reduce the droop to 1mm (I used redwood, young growth which corresponds to a reasonable, knot-free joinery grade here)

Note that if the load is centred then the sag is often double that of an evenly distributed load and that I've used "real world" adjusttments in the calculator

BTW My advice would be to put a batten across the front of the shelf

 

[PingCrosby]

Hi

Thanks for the reply. I looked at the sagulator but could not find "ply" in the drop down for wood type!

For the front baton is there any particular join I should use?

 

[Deleted member 174758]

Thanks for the reply. I looked at the sagulator but could not find "ply" in the drop down for wood type!

Bottom of the list, "Plywood, fir". It's American so they use a few terms which seem odd to us, like "Melamine" for melamane faced chipboard (MFC) and "Particleboard" for chipboard and so on

For the front baton is there any particular join I should use?

"Properly£ done a halving joint, but to be honest a pair of angle plates with 1-1/4in screws would do just as well in practice and probably look better to boot from the front

 

[foxhole]

Depends how close to the edge of the board the wardrobe will sit, within a few cm's and should be fine but strength in centre of board will be very weak.Putting 2X1 across the front and center will give extra strength.