Span between brackets for birch ply shelf

[ol_london]

I’m planning some quite deep and long shelves in 24mm birch ply and would appreciate advice on the span for brackets please... if I get it wrong it’s going to be an expensive mistake.

The main problem is the wall is plasterboard.

The plan is for 2m long and 25cm deep 24mm ply shelf. Not sure yet exactly what will be on them but let’s assume a heavy load for some sections, ie books.

My guess would be three metal brackets: on ends and one centre but seeing as it’s plasterboard would four be safer? Visually I’d prefer three.
Thanks

 

[Jameshow]

I'd think 25mm over 1m should be fine.

18mm would be doubtful but 25mm is fair bit stiffer.

Cheers James

 

[ol_london]

I'd think 25mm over 1m should be fine.

18mm would be doubtful but 25mm is fair bit stiffer.

Cheers James

Thanks James

 

[Myfordman]

I'd be guided more by the stud positions that are likely to be 400 or 600 centres. Both of which should be fine with 24mm birch ply
No good having a stiff shelf that pulls out of the wall under load.

 

[Sebb]

+1 on where the studs are will decide, sagulator is good for checking any likely issues with sagging: The Sagulator – WoodBin

 

[TRITON]

You can just glue another piece to the underside at the front, effectively doubling the thickness and adds considerable strength to prevent sagging. @2m its likely, depending on the weight placed on it it could sag over time and just the nature of wood/mdf/ply. You can add a moulding to this added strip to give a bit of detail.
Much like the underside of this mantlepiece. The top is 19mm, the added section is 19mm, so from the front it looks thicker, and i used a panel raising bit to thin the impression of it at the leading edge.

 

[pils]

+1 on where the studs are will decide, sagulator is good for checking any likely issues with sagging: The Sagulator – WoodBin

"The Sagulator" Genius! Didn't know about this and the name is brilliant!

 

[recipio]

Is Baltic ply available in 24 mm or will you laminate 18 +6 mm ? It will be heavy !

 

[ArferMo]

1/5th to the first support from the end, then 3/5ths to the next support, then 1/5th gives the least deflection assuming even loading across the whole shelf. It's engineering!

 

[shed9]

If there are multiple shelves and the relative proximity of them is close together you could use that to your advantage and do away with traditional brackets, i.e. use interconnected vertical sheet taking advantage of the full length of the studs.

 

[ol_london]

1/5th to the first support from the end, then 3/5ths to the next support, then 1/5th gives the least deflection assuming even loading across the whole shelf. It's engineering!

This is interesting, I’ve never heard this rule. So over 2m, 1/5 is 40cm and you are saying:
40cm in from edge, then 3/5 is 120cm, then 40cm. Would that not look unbalanced? Or maybe I am not understanding..

 

[ol_london]

I'd be guided more by the stud positions that are likely to be 400 or 600 centres. Both of which should be fine with 24mm birch ply
No good having a stiff shelf that pulls out of the wall under load.

Great point. Only it’s a new build and not sure if the studs are metal...I think they probably are. Cheap and easy for the developers but how can you hang stuff??

 

[Myfordman]

Find out what you have and use the correct fixings. Fixing into stud will always be stronger than into plasterboard.

 

[Garden Shed Projects]

As with most things it is important to use the appropriate fixings. I wouldn't advise fixing into the stud if they are metal as a plasterboard fixing would provide you with a better load. You will be fine if they are timber. I have had good results with Grip it fixings into plasterboard-

https://www.screwfix.com/p/gripit-p...WosZx-AeeuIaJIw3F-oaAv7rEALw_wcB&gclsrc=aw.ds
This is a great little trick for finding studs if you don't have a stud finder available. I have tried it and it works a treat as the screws are slightly magnetised.

 

[gmgmgm]

1/5th to the first support from the end, then 3/5ths to the next support, then 1/5th gives the least deflection assuming even loading across the whole shelf. It's engineering!

This is interesting, I’ve never heard this rule. So over 2m, 1/5 is 40cm and you are saying:
40cm in from edge, then 3/5 is 120cm, then 40cm. Would that not look unbalanced? Or maybe I am not understanding..

They are called Airy (or Bessel) points depending upon the precise goal: Airy points - Wikipedia Very clever maths, but 1/5 in from each end is a good approximation. It's intended to support a beam (shelf) with two perfect points.

However, you may want more than 2 supports (with less overhang at the end), or prefer a different look. Books are really heavy, so a support at each stud might be best.

 

[baldkev]

I have a few neodinium rare earth magnets. I use them to locate screw heads in p.b ..... ceilings, walls, its quick and easy to find the screw runs. A 30mm cylindrical one is great, but even 10mm x5mm usually have enough pull


Edit: i put in the wrong quote