Long alcove shelves - design question.

[Setch]

I have a customer enquiring about some alcove shelves to fit a 1.9m wide alcove. They will probably be used as book shelves, at least in part, so potentially quite heavy loading.

The design they have suggested is a fairly conventional looking alcove shelf, which I would normal build as an MR MDF box, fitted to concealed battens on the three alcove sides, but they would prefer the shelf full width *without* any partitions or supports. Visually this does look very striking, but their are obvious issues with sag over such a long span.

Does anyone have experience with shelves this long? As I see it my options are:
- chunky solidwood front to the shelf (25 x 55 tulipwood?)
- metal reinforcer (Alu? Steel? Box or angle?)
-Insist on dividers, and try and settle on a design which isn't too obtrusive.

Any thoughts gratefully received, especially from anyone who has done this.

 

[Argus]

I had an inquiry similar to this some years ago. If I recal the span was in the order of 1.5 M........ in a listed house.

On the basis that the customer is always right (even when he's wrong) I plumped for a box construction of ply, eventually painted to match the decor; under the bonnet, the internal sections were reinforced with a frame of welded steel T-bars running longitudinally.

I had to incorporate the anticipated weight of a full end-to-end population of books, plus the weight of the shelves (there were four of them) and the anchor points at each end and hidden anchors at intervals along the back.

Over the top? Possibly. Ostensibly it was a bookshelf, but who know what would end up on it - I didn't.

Add to the price of my materials, time, reasonable profit etc, then the cost of others making good after all the structural stuff and painting. I advised that he should consult the relevant authorities on the listing issues and give it to me in writing.

I was determined that none of this would become detached. However, it all fell down (sorry about that!) on cost.
....... confronted with the reality of the job, my esteemed client thought again and I never heard the outcome.

Moral?
Do it right or not at all. There's no point buying a huge headache by simplifying the patently difficult.
So, over that span, steel T-bars or box section frame . NOT Aluminium! A professional opinion on loading would be useful in designing the metal frame.

Good luck

 

[Sheffield Tony]

So, over that span, steel T-bars or box section frame . NOT Aluminium! A professional opinion on loading would be useful in designing the metal frame.

^^This - even metal deflects under weight, over 1.9m it is probably worth guessing the load and the tolerable displacement and working out what you need. It might be bigger section than you would expect !

 

[thomashenry]

I've got 2m long shelves in my kitchen that are just planed scaffold boards, with concealed battens on the ends and are very simply supported along the back by three evenly spaced coach bolts in the wall whose heads sit proud of the wall and slot into holes drilled into the back the shelves. Cheap, simple, quick, looks good and is solid.

 

[Setch]

Well, I finished them a couple of days ago, time will tell if they sag or not, but I'm very hopeful given how rigid the finished shelves were.

I built in 20mm mild steel box section in the front edge of each shelf, glued with polyeurethane glue to the top, bottom, and front edge of the shelf. Each shelf weighed about 20kg, which made single handed installation fun!

 

[Droogs]

looks smart Setch, nice finish on the paintwork