Author Topic: 1m x 1m x 1m ply box - how heavy can it support on top?  (Read 2027 times)

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Offline eddomak

  • Posts: 250
1m x 1m x 1m ply box - how heavy can it support on top?
« on: January 30, 2017, 09:20 PM »
I have just started planning the construction for a bedroom renovation for my daughter, where the design has been done by an interior designer friend.

Part of the design is a set of large drawers (drawer area = 1000mm wide x 700mm)  directly underneath a platform area (ie another piece of 18mm plywood on top) upon which people (1 at most) are expected to walk over or sit upon (or kids will probably jump up and down on).

I was wondering if it would be sufficient to construct a basic 18mm plywood carcass for the drawers (top dimensions 1000 x 700) and would this be strong enough on its own to support the load above it without sag / bounce / flex / breakage? It is likely that the platform could also rest on a bearer that is dynabolted to the wall to distribute the load if this helps add some context to the situation.

I am guessing that if it is not strong enough I would either need to:

1) increase the thickness of the plywood (any suggestions?)
or
2) construct a load bearing frame (which would not be visible) around the cabinet carcass to support the platform above it

As always, thanks in advance for your helpful suggestions and experience.


« Last Edit: January 30, 2017, 09:24 PM by eddomak »

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Offline Tim Raleigh

  • Posts: 3438
    • Oakville Cabinetry
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #1 on: January 30, 2017, 10:09 PM »
As always, thanks in advance for your helpful suggestions and experience.

A drawing of the planned structure would help to advise you. I recently made a 35"x35"X11" platform from 13mm ply that held my weight (200lbs.) although I wouldn't jump up and down.
Tim

Offline Alex

  • Posts: 5388
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #2 on: January 31, 2017, 02:07 AM »
If I was expecting people to walk over such a thing I'd definitely build a support frame.

Offline eddomak

  • Posts: 250
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #3 on: January 31, 2017, 08:25 AM »
A drawing of the planned structure would help to advise you. I recently made a 35"x35"X11" platform from 13mm ply that held my weight (200lbs.) although I wouldn't jump up and down.

Indeed it would.  ;D I was hoping to avoid too much Sketchup work, but anyway, I hope this helps.
Access to the green bed area will be across the pink shaded area, which is directly above a set of 4 drawers.
I was hoping to just rest the platform on top of the carcass the holds the 4 drawers.


Offline DrD

  • Posts: 395
  • I might not be fast BUT I sure am slow
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #4 on: January 31, 2017, 09:06 AM »
@eddomak

I build structures similar to your bedroom suite, and they are all framed by 2 x 4 stock with 1/2" birch ply for no-load-bearing surfaces, and 3/4" birch ply for load- bearing; it may be overkill, and that's ok with me.  This way I have confidence that whatever weight, within reason for the application, will not result in sag over time.
Dr.D

Offline eddomak

  • Posts: 250
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #5 on: January 31, 2017, 07:42 PM »
I build structures similar to your bedroom suite, and they are all framed by 2 x 4 stock with 1/2" birch ply for no-load-bearing surfaces, and 3/4" birch ply for load- bearing;

Thanks for your experience on this. I think I am leaning towards that solution (framing with 2 x 4) as well as it is a sure thing. In the end the structure is large enough to accommodate that solution.

One thing I have learnt from Ronin "Whenever there is any doubt, there is no doubt."  [big grin]
« Last Edit: January 31, 2017, 07:52 PM by eddomak »

Offline DrD

  • Posts: 395
  • I might not be fast BUT I sure am slow
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #6 on: January 31, 2017, 07:53 PM »
Love that movie!
Dr.D

Offline eddomak

  • Posts: 250
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #7 on: February 01, 2017, 09:18 AM »
OK, this is probably close to what I will do...


Offline DrD

  • Posts: 395
  • I might not be fast BUT I sure am slow
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #8 on: February 01, 2017, 09:46 AM »
@eddomak 

Nice looking project.  Looks like you plan on drawers of slightly less than 4' (~45in or 1150mm).  It has been my experience that long horizontal runs of 2 x 4s benefit from vertical supports.  If this can't be worked into your design, perhaps some angle iron, horizontally &/or vertically could be used - don't know how you are with welding or if you have contacts who can do simple welding.  But, there I go over-building again.

DrD
Dr.D

Offline eddomak

  • Posts: 250
Re: 1m x 1m x 1m ply box - how heavy can it support on top?
« Reply #9 on: February 01, 2017, 08:44 PM »
Looks like you plan on drawers of slightly less than 4' (~45in or 1150mm).  It has been my experience that long horizontal runs of 2 x 4s benefit from vertical supports.

Yes indeed, I am in total agreement (but was too tired at 1:30am to add in that detail at this stage). Even though the bed cavity will act as a stressed member to transfer some of the support to the drawer carcasses (and to some further support underneath them, I will be putting in some additional 2x4 vertical supports (maybe one between the drawer carcasses. In addition to this, the member that is against the wall will be fixed into the masonry wall.

Which actually leads to the next question (which probably needs another picture, and more Sketchup work ::) ) What is standard practice in relation to dealing with the skirting board? I would like the top member of the frame to be secured to the wall, but the existing skirting board will then not allow the bottom member of the frame to be hard up against the wall. Do I:

1) remove the existing skirting?
2) somehow offset the lower member to allow for the skirting? (ie the top rectangle of the framing is different size to the base rectangle, and the rearmost verticle supports would not be hard up against the wall).
3) do something else?

Thanks again for your comments. All appreciated.