Shelf

[whyme!]

I am looking to make a shelf to span a 2.4m window supported each side on wooden Corbels. Shelf will be 20 cm wide. Would 25mm mdf be rigid enough or would i need something thicker.

 

[Deleted member 174758]

Personally I'd rather go for something like 38mm (1-1/2in) or thicker softwood for the corbels and 25mm or thicker softwood for the shelf. At 2.4 metres, though that shelf will need a fair amount of additional support such as sitting on top of an architrave or using inverted angle brackets (if needs be recessed into the underside of the shelf and buried beneath the plaster to the rear of the shelf). If you'd like to see for yourself how much saw there is in a shelf like that (without intermediate support) then key the figures into the Sagulator

 

[Doggit]

As the corbels will sit either side, there obviously isn't an chance of getting one (at least) in the middle, so MDF is completely out, and even 38mm might deflect on that width. It's possible that you could fit an angle bracket on the top side of the shelf, rather than the bottom,

 

[whyme!]

As the corbels will sit either side, there obviously isn't an chance of getting one (at least) in the middle, so MDF is completely out, and even 38mm might deflect on that width. It's possible that you could fit an angle bracket on the top side of the shelf, rather than the bottom,

I was thinking maybe a bracket mid span on top. The bottom is not possible as shelf will be running along top of window opening. Might need to look at some planed 50mm timber. My Corbels are 300mm high x 200mm projection x 94mm wide. The Sagulator says 25mm MDF on that span and depth ACCEPTABLE

 

[rsgaz]

The Sagulator says 25mm MDF on that span and depth ACCEPTABLE

But you've typed in 25 centimetres for the thickness, change it to 2.5 and try again.

 

[whyme!]

But you've typed in 25 centimetres for the thickness, change it to 2.5 and try again.

Oh yeah! OK back to the drawing board lol Although shelf load will be negligible just a few decorative items (glass)

 

[foxhole]

If you put a 2x1 on the front edge ( above or below) then you can use thinner shelf.

 

[whyme!]

If you put a 2x1 on the front edge ( above or below) then you can use thinner shelf.

like some decorative end piece, kitchen cornice or similar good idea as i have a length of cornice left over

 

[big-all]

cornice will sag you need timber
mdf/chipboard etc has no grain to give strength

 

[Deleted member 174758]

If you put a 2x1 on the front edge ( above or below) then you can use thinner shelf.

Probably to put it along the back edge like a sort of upstand. That would add rigidity as well as giving the OP something to fix through into the wall behind