Extra wide floating shelves - how to fix!

Tom99

IvyFlood wrote: »

They're just metal prongs, but the length of them looks too short to support the shelf

I don't think longer prongs would help, its the leverage effect of a wide solid wood shelf with books on top. Some way of supporting the sides needs to be found.
What about one of these:
https://www.screwfix.com/p/corner-braces-zinc-plated-25-x-25-x-16-5mm-10-pack/11529
One each side set back from the front say 50mm. The part you screw into the wall can be hidden behind the shelf.

getmore4less

How thick are the shelves?

you also don't say how wide they are.

if thick enough to take a support tube then each side can have a groove routed into the edge to take another invisible support.

Rear only brackets probably need to hold 25kg-35kg per metre.

something like this is good for upto 40kg per bracket
https://www.bespoakinteriors.co.uk/shop/hardware/heavy-duty-floating-shelf-brackets/

Fitting

For installation of these heavy duty floating shelf brackets we recommend a 14mm hole to secure the main shelf pin and two 8mm holes for the retaining screws. To achieve the 40kg load rating we also recommend that you install the shelf brackets using our chemical resin method. Please head to the “Video” tab above for fitting and weight testing videos.
For our heavy duty floating shelf brackets we recommend using three fixings per meter of shelf. This is based on a typical 400mm depth oak floating shelf. However you should use your own discretion when calculating fixing spacings. Fixing quantity should be based on the expected shelf usage and strength of the wall.

getmore4less

I found this reference to get an idea how much books weigh

Weight of books

The average weight of standard books per 500 mm run:

Small paperback 8 ½ X 5 ½ inches 10.29 Kg

Small modern compact paper backs 8 ½ X 6 inches 15.7 Kg

Small hardback older book 9 X 6 inches 11.84 Kg

Medium hardback book 10 X 7 ½ inches 17.4 Kg

Large hardback book 12 X 9 ½ inches 37.2 Kg

Norman_Castle

My question is, have we made the wrong decision getting them made this way and is it impossible for them to be floating due to the size?! I’d rather them not sit on wooden ledges and not sure this is possible anyway as the chimney breast wall will be full of pipework to drill into.

If the shelves reach the edges supporting them at the sides is much stronger. Fit pins or small brackets to the wall hidden by cut outs in the bottom of the shelf or use narrow battens hidden by cut outs under the shelf.