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I am building a memorial bench out of live edge slabs. I liked the idea of the 'legs' matching the form and style of the seat and seatback slabs, so I decided to cut them out of my scrap slabs. Either side of the seat slab will be corner notched, and the notches will rest in the side pieces. The seatback will have a notch cut for the armrest and will be screwed to the side pieces. The seat and back will not extend more than an inch past the side pieces.

This outline shows my initial design for the side pieces. As the pencil marks are difficult to see I've created a second photo where I messily highlighted the cut lines in purple.

Side piece cuts Side piece cuts highlighted

Are there any potential structural, construction, or even aesthetic issues with this design? I am aware that in a perfect world the wood grain should run at an angle down the legs to maximize strength, but given than I'm cutting this out of a single slab that's not possible. The legs are just under 2" at their thinnest point, which I believe should be sufficient to hold the bench and users?

This slab is approximately 1.5" thick, kiln-dried Cherry (approximately 7% moisture content). I am attempting to utilize as much of the natural edge as possible so the edges will not be cut straight; bark will be removed completely and the edges lightly sanded. Epoxy will be used to fill the cracks.

The armrest will be heavily sanded on each side to provided rounded edges for comfort, and is approximately 1". The seatback posts are sloped back at a 5 degree angle and approximately 2" at their thinnest point.

The underside of the seat will have two pressure treated 2x4s running the length and attached to the side pieces. An additional scrap piece of slab (approximately 1.5" x 3") will be run at the lowest center point to provide additional lateral stability.

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The armrest section is quite thin and also the grain is oriented at 90° to what you'd normally expect for an armrest. I would expect this to split with time due to expansion/contraction (and in fact you already have a split in the timber here.

What you have here with the large slab end is typically known as a "pew" like you might have in a church. If you do a google image search for "wooden pew" you will see that they pretty much never have this hole cutout under the armrest portion or if they do, they leave a much thicker section above.

Here are some examples:

enter image description here enter image description here enter image description here

As you can see, the last one there does have a cutout but it's left a few inches of material above.

Something else you might be able to do is this:

enter image description here

i.e. adding an extra piece of timber on top of the armrest with the grain going the "correct" way. I realise there are no cutouts in this picture but there could be. I'd still probably want to leave at least 2" of thickness to the main slab part of the armrest though to avoid splitting, personally. You may get away with less but it depends on how dry the timber is, what kind of fluctuations in temp/humidity it might be subjected to etc.

Other than that I can't see any obvious problems with it.

  • Thank you. I had metal bench designs in mind when working on this so I hadn't thought of splitting across the armrest. Assuming I wanted to maintain the existing design if possible, what minimum thickness would you recommend for the armrests? – Nicholas Jun 26 '18 at 14:25
  • Have updated with a bit more info and another idea. – WhatEvil Jun 26 '18 at 14:32
  • Another weak point will be where the "back" piece of the side meets the lower side. Leaning back on the backrest will create a lot of leverage to split the grain in this area. – SaSSafraS1232 Jun 26 '18 at 20:36
  • @SaSSafraS1232 I was a little worried about this too, which is why I made it 2". I was wondering if it would help to attach a pressure treated 2x4 to the side piece at the top and at the bottom to transfer some of the forces downward, but to do that I would need to make the back part of the side piece completely flat I think. Do you have any other suggestions to help deal with this? – Nicholas Jun 27 '18 at 14:01
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    You could just put a large-ish radius round on the internal cutout here. The weak point is gonna be at the internal sharp corner so if you replace the sharp corner with a round you're adding more material back to the weak point. – WhatEvil Jun 28 '18 at 10:58

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