2.2m Alcove floating shelf question

[Stripee]

I've previously built floating alcove shelves across a 3ft span. I used 18mm mdf above and 4mm mdf below, supported by battens attached to all three walls and across the front, with a couple of intermediate supports. However this next project feels like a completely different animal...

My wife wants me to build two alcove shelves in our living room. The alcove is 2.2m and shelves will be 23cm deep. It'll be used for potted plants and probably end up being about 30-35kg of weight going on it.

Thankfully it's brick on all three sides.

I'm wondering what timber to use to ensure no sagging?

 

[Deleted member 174758]

A hard hardwood such as oak (as opposed to a soft hardwood like balsa) will be the best choice, followed (in decreasing order) by softwood, hardwood plywood and MDF. Adding a hardwood (or even a softwood) deep lipping to a sheet material shelf can stiffen it up a lot. Using more brackets at lesser centres also helps. A lot depends on cost, though

Google "the Sagulator" and key in various sizes and species to get some idea of potential sag for a given shelf.

 

[foxhole]

I made similar (30cm width) . Used two 18mm mdf section sandwiched around 20mm baton . Baton flush at front and hidden behind veneer trim . Section of baton on the wall and inset baton on side and rear of shelf so the shelf then slides onto the baton which is screwed to wall .