What to consider when using slab wood? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 9 Old 08-05-2011, 01:26 PM Thread Starter
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What to consider when using slab wood?

A friend of mine has recently started building furniture primarily out of slab wood and selling them for quite a bit. Although the sizes vary, I'd say they are generally 3-4" thick x 12-18" wide x 4-8' long. He is relatively inexperienced when it comes to working with wood and my fear is that he is not considering the long term. What he's essentially doing is buying a variety of wood species, some recently milled, then sanding and finishing them (not sure of finish or top coat products but typically a gloss finish). He then usually installs welded metal legs to them and that's about it, really. It's kind of a rustic/modern combo look. The selling point, of course, is the big hunk of wood. While they look good now, I am not sure that will last.

Although I am no expert, I did advise him that wood tends to move as it ages, which may not be evident now, but he could have some really PO'd customers down the road here. He seems to think that the wood is dry enough, but I doubt he has any empirical proof of that (i.e. moisture meter or similar).

Please correct me if I am wrong, but for more "modern" furniture (although the economy of using smaller joined pieces is part of it) another really good reason to use small joined pcs is to overcome the internal stresses of the wood.

So my question is, what things do you need to consider when building with wood slabs? How long should they season (which I'm sure depends greatly on many things). I tend to think that the slabs will at least start to split and twist as they dry out.

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post #2 of 9 Old 08-05-2011, 02:20 PM
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Thick slabs like that are much more unpredictable than slabs say 1-1.5".

The Sawyers here will be better versed in this, but from and end builders perspective you can start by being certain the slab is entirely dry, 4-6% at the absolute min and stable before jointing / sanding.

Another factor to consider is grain, grain run-out and knots as it affects move movement.

To minimize splitting the top should be floating via z clips, slotted cleats or similar.

At the end of the day though, moisture and temperature changes may or may not split, twist and warp the slab.

~tom ...it's better to remain silent and be thought a fool than to open one's mouth and remove all doubt...
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post #3 of 9 Old 08-05-2011, 02:36 PM
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Quote:
Originally Posted by ChiknNutz View Post
some recently milled,
...I don't like the sound of that. Recently milled to ''dry'' most woods shrink 10% for one thing, some even more. I just plugged in a random species, red oak, from 35% MC (recently sawn) to 5% MC (in my house in the winter)...an 18'' wide slab is going to shrink 1 3/8'', or in other words be 16 5/8'' when ''dry'' http://www.woodweb.com/cgi-bin/calcu...ator=shrinkage I don't know what kind of wood he is using, but there is the calculator.

This shrinking can be just that, a reduction in size...or it can really go nuts as it dries (depending on species and the way it was sawn, some woods are tamer and 1/4 sawn anything is tamer than flat sawn anything) 3-4'' thick is going to take a couple years, at least in my neck of the woods, to be anywhere close enough to be made into furniture that is coming inside. Or kiln dried. These from the sounds of it are just slabs on legs, not fine joinery, so it's not as bad. But still if he is putting a finish on them, you said high gloss, well it is not going to shrink the possible 10% or more and the whole thing goes to crap. I could type more, but let's just say if he is using ''wet'' wood, yes I too think he is headed for some unhappy customers down the road (about winter time when the furnace is running and the houses are real dry) I would not bring a slab of wood in the house over 10% moisture content without expecting some kind of movement in the wood. (he needs a moisture meter) Either simply shrinking...or literally splitting wide open with a violent and loud bang=seen it happen.

Quote:
Originally Posted by ChiknNutz View Post
Please correct me if I am wrong, but for more "modern" furniture (although the economy of using smaller joined pieces is part of it) another really good reason to use small joined pcs is to overcome the internal stresses of the wood.
Nah, I build with WIDE lumber and thick slabs almost exclusively...That has been properly dried, no problems.

.

Last edited by Daren; 08-05-2011 at 11:08 PM. Reason: added ''MC'' to clarify
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post #4 of 9 Old 08-05-2011, 02:55 PM
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Quote:
Originally Posted by Daren View Post
...I don't like the sounds of that. Recently milled to ''dry'' most woods shrink 10% for one thing, some even more. I just plugged in a random species, red oak, from 35% (recently sawn) to 5% (in my house in the winter)...an 18'' wide slab is going to shrink 1 3/8'', or in other words be 16 5/8'' when ''dry'' http://www.woodweb.com/cgi-bin/calcu...ator=shrinkage I don't know what kind of wood he is using, but there is the calculator.

This shrinking can be just that, a reduction in size...or it can really go nuts as it dries (depending on species and the way it was sawn, some woods are tamer and 1/4 sawn anything is tamer than flat sawn anything) 3-4'' thick is going to take a couple years, at least in my neck of the woods, to be anywhere close enough to be made into furniture that is coming inside. Or kiln dried. These from the sounds of it are just slabs on legs, not fine joinery, so it's not as bad. But still if he is putting a finish on them, you said high gloss, well it is not going to shrink the possible 10% or more and the whole thing goes to crap. I could type more, but let's just say if he is using ''wet'' wood, yes I too think he is headed for some unhappy customers down the road (about winter time when the furnace is running and the houses are real dry) I would not bring a slab of wood in the house over 10% moisture content without expecting some kind of movement in the wood. (he needs a moisture meter) Either simply shrinking...or literally splitting wide open with a violent and loud bang=seen it happen.



Nah, I built with WIDE lumber and thick slabs almost exclusively...That has been properly dried, no problems.

.
yrs ago i cut lot's of lumber and if it isn't kiln dryed he is going to be disapointed when the coustomer come's back and want's the crack's fixed. He isn't going to be that lucky and not have neg. feed back. I built thick stuff but with kiln dryed wood. Wet or very high wood Moisture is going to be a problum .
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post #5 of 9 Old 08-05-2011, 03:00 PM
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So long as his customers don't expect stability or precision then he should do fine - but that wood is going to warp and move, like Daren said. Putting the finish on was a bad idea. Leaving it raw, then selling them as workbenches would have been smarter IMHO.

Rob

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post #6 of 9 Old 08-05-2011, 08:13 PM
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If the wood was green he's going to have a bad rep pretty soon.

I was at an auction where there were 40-60 slabs. I went with the intention of buying crotch slabs to turn into tables. Well, I noticed right away that there were no dates on the material, when it was cut, etc. So, I'm thinking this stuff probably needs a good 3-4 years + to dry and I said screw it. Not for me right now.

I have worked with thinner slabs I know are dry and so far so good. The thick stuff really intimidates me because I know what can go wrong.

I hope nobody comes back with a twisted top.
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post #7 of 9 Old 09-01-2014, 10:04 PM
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Sufficient time has passed. What's the update on these tables and the craftsmans reputation?
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post #8 of 9 Old 12-03-2014, 01:18 AM Thread Starter
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He's done surprisingly well. He is really more of an acquaintance than a friend so I haven't been in close contact as this has progressed. However, he did say he made sure they were dry via moisture meter. It also sounded like he found someone to kiln dry these so I guess he understood the pitfalls after all. He partnered up with a guy that seems pretty sharp. Check out their website at elpisandwood.com.

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post #9 of 9 Old 10-17-2015, 09:53 AM
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Recently stumbled onto the beauty of slab wood. Now I have about 20 slabs cut from some old elms this summer. What moisture content do I need to see before I can start sanding and playing with it. Have some popular given to me at 16%. Elms is mostly 36%.

Thx
Kim
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