Max width of carcass than can be sat upo
I need to make a low bookshelf which can be sat upon. Since it’s going to be painted, I plan to use 3/4″ MDF with hardwood trim. The height and depth of the bookshelf is fixed at 22″ high by 19″ deep (with an adjustable shelf in the middle). What I would like to know is, how LONG (width) can I make the bookshelf just using the two 3/4″ sides and back as the vertical support. I expect that no-one more than 250lb will sit on the bookshelf. I’d like the back to just be 1/4″ ply but I can use something thicker (eg 1/2 to 3/4″ MDF) if need be. The sides would be rebated into the top and bottom (3/8″) and glued and screwed for strength. The back would be glued into a rebate all around the back to make it flush.
The request is that I get at least 25″ width inside – can this be done?
Where would one find books/advice on structural information such as I am requesting?
Replies
I can't give you a scientific measurement on how long your bookcase can be but understand that the strength of the front of the bookcase will come from your hardwood trim and not the mdf itself. You say the depth of the bookcase is 19" and you'll have the back fit into a rebate/rabbet that you would like to be 1/4" thick. 19" is a pretty deep bookcase and you'll absolutely need to have the back a 3/4" mdf solid panel that supports the top or it will sag when someone sits on it since the majority of the weight will be in the back. So basically, you'll have to build a big box out of 3/4" mdf and put some trim on the front of it.
The trim on the front should at least be 1 1/2" wide or it will have a tendency to bow with the top. You didn't mention what the trim would be but it would have to be a hardwood with tight grain like oak. If you used a hardwood like poplar where the grain is not as strong against downward pressure, your top will be too weak to support the weight of a heavy person.
I would play it save on the length and make it no longer than it needs to be. Probably about 36" long.
Thanks, Especially about the backboard being 3/4" MDF rebated in. I need 24" in width, so I'll feel safe with that.I'll probably use Mountain Ash (Australian straight grained hardwood) for the trim. When you say 1 1/2" wide for the trim do you mean 1 1/2" x 3/4" by whatever long?
Yes... 1 1/2" may be overkill considering the size of the bookcase but I wouldn't make it any less than 1" wide.
If you add a center vertical support you will eliminate the deflection problem in the seat and you probably could stay with a 1/4 in back.
I thought I'd post a picture of the finished bookshelf/seat I used 1.5" x 3/4" ash as the trim. The outside bays are 24" and inside bays are 12" wide.Again, thanks.Burn
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