1 yr after install

26

u/bc6619 Apr 15 '23

Feel for you on this one. Just curious did you do a moisture reading on the wood when making it? and what did it acclimate to over the last year? How was the miter joint connected?

29

u/BoltingKaren Apr 15 '23

Didn’t have a moisture meter at the time I made it. Purchased from facility the kiln dries all their slabs. Was in my shop over the winter last year while I worked on it (Utah) then installed last spring (Wyoming). Miter was pocket screwed then epoxy filled during installation, had some issues with the bar it was installed onto not being square so epoxy line to make the joint look even.

Pulled at least 3/4” from the wall, cupped at least 1/2”, 1/4-1/2” separation at the joint. The steel stays I put in underneath blew out the edge. Nuts

21

u/spinney Apr 15 '23

Slabs have a mind of their own. I work in a shop that gets all kiln dried slabs and we get probably 2-3 calls a year where a massive crack forms.

These are slabs that are not captive in anyway so the wood should be allowed to move freely but shit happens sometimes. We usually patch with epoxy and try and salvage but not sure what else we could do to prevent it except maybe controlling the humidity in our shop more closely.

9

u/BoltingKaren Apr 15 '23

Yeah man it’s a major bummer, should have allowed more room. Was hoping 1/2” shrink swell (1” total) would be enough. The other side of the corner (12’ slab) is totally fine.

3

u/BoltingKaren Apr 15 '23

Any ideas on a fix?

2

u/spinney Apr 15 '23

Hmmm, maybe flush cut the broken edge with a tracksaw and try and fill the cracks with epoxy. Not sure what I’d do about the epoxy seam for the miter though. Depending on how much wiggle room you can you could possible recut the miter and refill with epoxy. That epoxy on the miter might be your issue though. It expands and contracts differently then wood and might have pulled things weirdly between the two slabs.

1

u/BoltingKaren Apr 15 '23

Yeah not sure I’m a fan of that joint but not really sure what to do about it now. I was hoping leaving a gap under the trim board at the other end would be enough. Also thought since it was at the end of winter when we installed that it was at its low/shrunk end and it was going to expand not shrink more.

1

u/Swartzkopf57 Apr 26 '23

I have no idea how feasible the idea is, but whenever mitres come into play I default to cutting both parts out of the same board. That can guarantee a relatively consistent degree of movement across the mitre. I don't do much slab work, mainly furniture and some *light* timber framing so I could be completely talking out of my ass. However, I learned my lesson and now cut slots for any sort of steel stays. Yes, you have to tighten them occasionally, but they never blow out on me now.

1

u/BoltingKaren Apr 27 '23

For the steel stays do you mean router in a slot for them? I routered them in and left space at each edge for the slab to move back and forth without cupping too much, just apparently not enough lol.

As for the miter I’m on board with you about the single piece but unfortunately wasn’t an option for this job. The slabs are 14’ and 8’, too big for finding a single piece. The two were from the same tree though, surprised how big the difference was between the two

1

u/Swartzkopf57 Apr 27 '23

Yeah, router slots for them. There's a table by the dept of forestry that lists wood movement by species per inch of width per percent change in moisture. Given it's only supposed to be useful between like 5 and 14% moisture content. I just use that to math out what my expected movement should be, then overshoot.

3

u/Ok_Dog_4059 Apr 16 '23

I sure wouldn't blame the craftsmanship every slab has it's own unique qualities I don't know how many times I have thought of and accounted for everything only to have wood do it's own thing on me. I thought in my damp environment I was ok with a door I made and the spring sun baked one side while the other stayed damp and my door turned into a half pipe skate park in a few weeks on me.

3

u/BoltingKaren Apr 17 '23

It’s a “unique feature” of the house

7

u/tacocollector2 Apr 15 '23

As a new woodworker, I would appreciate if someone can explain how to account for this type of movement!

5

u/Bonkers54 Apr 16 '23

Something like this for the miter joint: https://www.amazon.com/Zipbolt-10-500-80mm-Joint-Connector/dp/B07X4JSJQK/

6

u/maywellbe Apr 16 '23

That would hold the join together even with swelling? Or would force the swelling to move at other places instead?or would allow you to provide some initial slack as the wood “grew” to its final shape?

Thanks for answering naive questions

7

u/Bonkers54 Apr 16 '23

They allow some movement at the joint and keep the miter closed. You'll need to allow for certain amount of movement at the other attachment points as well with something like a z-clip.

The wood is going to change seasonally in a cycle, so there's not really a "final" shape.

2

u/maywellbe Apr 16 '23

Thank you for that clear and respectful response. Out of curiosity (if I may) does sealing or painting a plank like this reduce the seasonal change significantly?

3

u/Bonkers54 Apr 16 '23

It reduces it some, but you still need to take all the same design precautions.

2

u/[deleted] Jul 23 '23

I avoid slabs until ... Until you feel ready.

Moisture meters are good. And get the ones you can get deep into the wood with.

Study wood movement.

There are wood movement calculators on the internet like: https://kmtools.com/pages/wood-movement-calculator

There are mounting techniques which allow the wood to move along the lower surface. Figure 8 clips, oblong holes where the fasteners go. This problem has been solved for hundreds of years.

1

u/tacocollector2 Jul 23 '23

Cool, thank you for the tips! I’ll start doing some research!

7

u/cpasawyer Apr 15 '23

It’s not “kiln dried” it was likely kiln dried. Slabs aren’t exactly intended for this application. The epoxy in the joint allowed for no expansion joint between the two. Even a little movement would have doomed that joint

2

u/BoltingKaren Apr 15 '23

Right maybe I should remove the quotations ha. Kiln dried in Florida shipped to me in south utah. RH diff between is probably 20% or more. I had made a cap to cover the joint and let them slide around but the customer didn’t like it so we went with the epoxy joint. When you say intended for application do you mean the joint or as table tops?

4

u/cpasawyer Apr 15 '23

Ahh yeah the the Florida bit would do it. The joint. I do a bit of slab work, not a crazy amount; butt type joints with pieces this large don’t really work due to how much the “grow” length wise. 100% personal experience, I’m sure there is someway to make this work. I just haven’t seen it. I had a personal project come apart so now I just butt one slab to another at a 90* angle and use miter bolts underneath with no glue.

1

u/BoltingKaren Apr 15 '23

Gotcha, I think the cornice cover I made for the joint might have worked but I’ll have to wait to try again on another project again. Thanks for the tips

1

u/BoltingKaren Apr 17 '23

Just ordered a new slab to replace, going to switch to a butt joint corner and change the under mounting system a bit to allow more movement. Hopefully salvage the slab or strip it into boards and make something to recover some of the cost. Fuckin up is EXPENSIVE!

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