Cleat thickness to support bench

I am building a 52" x 18" x 2" (actual dimensions) white oak bench for a small alcove that is surrounded on 3 sides by walls.
To support the bench, I am thinking of using white oak cleats along the 3 supporting sides and screwing up through the cleats into the bench so that there are no (obviousy) visible fasteners
Would a running 3/4" x 2" cleat along 3 sides of the bench be sufficient to support the bench under easonable use? (say maximum of 3 adults or 4 children sitting on it).
Assume that the cleats will be screwed into the studs every 16 inches using a 3 1/2" deck screw. Assume also that 3" deck screws will be used to screw up through the cleat into the bench.
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It should easliy hold the weight but *may* sag slightly.
http://www.woodbin.com/calcs/sagulator.htm
I think the sagulator only accounts for shelves supported on the ends not across the length on one side as you propose.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I have used the sagulator before but I don't really know how to use it when there is support on 3 sides. I would have thought that given that the bench is only 18" wide and that it is made of 2" thick White Oak that the sag would be really minimal.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Running a 3/4 ledger under the bench is a fine idea. No problem with strength as you describe. Personally I would use small lag bolts into the studs maybe 5/16" or 3/8". Screw pull-out would be your only concern here so the lags give more bite. The deck screws won't likely pull out but a commercial grade approach would use lags.
As far as attachment up to the bench, I would probably use table irons or other typical attachments like used for a table top. Across the 18" width you will get some expansion and need to account for that in a sliding attachment. Plus is seems difficult to screw up through a 3/4 wide board and that puts your screw at the very end and edge of the bench slab.
You could use pocket screws but that puts the screws even farther toward the end and edge.
Finally, you only need a little grab into the bench top, just enough to keep it from sliding or coming loose. Also, I don't think this would ever sag and in fact I would probably just put a ledger at each end but having it along the back will make it a littloe more stable.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I like that suggestion but my only concern would be whether I could still countersink the heads given that I have only 3/4" of depth.

Good point about allowing for expansion and about screwing up through a 3/4" board.
I am not familiar with the term "table irons" -- I tried googling but kept getting things like ironing boards and periodic table elements :) Can you describe what they are or give me another term that I could search on?

I guess my overall preference would be to have the fasteners as hidden as possible which is why I was initiatlly considering screwing up through the ledger board (note I can't use anything really thicker than 3/4" or else it will stand proud of the surrounding door trim).
So given your point that "you only need a little grab", are there other alternatives to providing a little grab (with room for expansion/contraction) while being minimally visible?
Thanks, Jeff

That was my hope, but wanted to confirm before I spent the $$$ and time on building it.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well with a lag you could do a 1/4" counter bore and the head would then sit under the surface and still have 1/2 of grab. That's plenty, but two deck screws at each stud will be just as good I suppose.
Here is a link to what I call table irons. Its an old term from original Stickley days, maybe outdated now. http://www.rockler.com/product.cfm?Offerings_ID=786 . They have an info sheet on how to install. I use a Forstner bit and make a round rabbit that hangs partly off the side of the table apron (or ledger in your case). But you can use a squared cut-out just as well.
If you are worried about sag, the sagulator says that a 500 lb center load will deflect (sag) 1/16 of an inch.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

And I believe that is without even taking into account the cleat on the back wall which should significantly reduce the effective span.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.