This past August we harvested lumber from a 100 year old granary at our farm. The lumber was plained on site and taken to an outdoor workshop where it was crafted into 4 beautiful 6’ x 3’ tables. Arranged together they make a stunning 12’ x 6’ conference table for our downtown Columbus offices.
Planks in the table tops were screwed and glued together and screwed to an Oak frame. The unstained tables were finished with tung oil to let the contrast of the Hickory, Red Oak, and Swamp White Oak planks stand out.
After a month or so in our conference room the tables began to split. All 4 tables have some splitting along the glue joints and or planks that have large splits. We pulled all the screws out of the table tops and now the tables are stacked in a storeroom as we figure out what to do now.
We have spoken with a number of people and received opinions as varied as “it should not have been framed, there was no way for it to shrink and expand,” to “that’s just what happens with Swamp White Oak, it always cracks,” to “it needed to dry inside the building for a year before putting the table together,” to “you can not mix woods.”
What is true? What do we do to stop further damage? How can the tables be repaired?
Replies
what do you do in this downtown office of yours?
Scott,
Solid wood expands and contracts across the grain with changes in humidity and temperature. There is virtually no movement in the direction of the grain. The amount of expansion and contraction varies with the species of wood, how dry the wood is, and what method was used to saw it at the mill. Although there is quite a bit of variation, it is not uncommon for wood to expand or contract, say, 1/8" per foot of width.If the table was glued and screwed together with no allowance for the movement of the wood, it will crack to relieve the strain. With a 3' wide table, you could easily expect to see 3/8" of change.
What to do about it? Well, I'd like to hear from some of the other knotheads, but I would take it back to the shop that made it and ask them to fix it. I can give you a better idea of possible fixes if you can show me a couple of pictures of the underside of the table where the frame is attached to the top.
Jim
This is wood technology 101. Wood shrinks and expands across the grain (width) and very little with the grain (length). This fact must be considered at the design stage so that all the wood moves together or the joinery needs to have the ability to slide with the movement.
This project was doomed when the end caps were put on perpendicular to the wide planks of the top thus preventing the planks from shrinking without pulling apart. I can't see in the photos how the top was fastened to the base but that could be contributing to the problem also.
Most woodworkers have experienced this type of shrinkage or expansion failure at some point and it can be a painful lesson. This was a pretty ambitious project for an amature woodworker but if done by a pro, he should have known better.
Good luck,
Bret
I think elementary rather than wood technology 101 would be the level to know that at
I'm often wrong, but the width of the crack suggests, to me, that the wood was too wet to be used. The crack looks to be more than 1/2" wide, which would be the average amount of seasonal change. Also, if the individual boards were each hard fastened to the frame/ends, I would have expected each board to crack slightly, rather than all at one spot.
My first suggestion would be to measure the moisture content of the boards. Essentially, they were air dried boards stored outside. Most recommendations I remember for "dry" wood stored outdoors is to bring inside and allow to continue drying fror six months. In the grainery the wood may have been protected from precipitation but likely still had too high a moisture content to use in furniture.
You might find some helpful information in one or both books by R. Bruce Hoadley.
cracks ... they look fine , leave them , That was one nice looking barn
I once had to replace a plank door I built because I didn't use slotted holes to attach the cross bands. I could not convince the purchaser that it didn't look that bad. The original door, cracks and all looks great in my shop being used for the door to the bathroom.
Bret
Say man,
I was hoping you could clarify your statement about the damage being the perpendicular endcaps. You correctly cite the expansion across the grain, so I am not sure why the perpendicular pieces would affect the gaps if the planks do not expand/contract with the grain (where the plank meets the endcap).
Or do you mean, if the planks were laminated to the perpendicular pieces, they might expand towards the middle, though not on the ends (as they are glued tight)? If so, should that be a t&g on the end? Floating not glued?
Thanks!
look at it as being in a large frame(as in a frame and panel). the wood has to be allowed to float inside of the frame( expand and contract) with out restriction. if this is achieved the material will live a long life with out cracking.. If it is restricted it will crack. as those end boards which run perpedicular to the top will not expand and contract lenghtwise.
it is difficult to see the construction to see how it was all put together, one is left to sumise what was done but the pictures give a good indication. one does not see any openings(cracks) at the edges. we can sumise that the top is fsatened to the edges by mechanical means as it is still tight there. as the wood loses moisture, that wood is going to shrink and when it shrinks, it is going crack at the points of least resistance which it did. those end boards are keeping the outer edges of the top at it's original dimensions.
it is unfortunate that so many people get involved with this industry and do not understand the basics of furniture construction as it has been known throughout the ages. the more info that is out there; the less we know. the other alturnative is to turn to the internet and ask a question and you really don't know if the person responding knows themselves
there used to be a fellow down the street form me who called himself a woodworker, who wrote tool reviews for a woodworking magazine. He plagurized a lot of his material. one day I went in there and he was applying some patse wood filler to some wood for an article and it was easy to see that he didn't know what he was doing, but he was writing an article on it. criminal but there is a lot of this happening. he did go on to be editor of the magazine!!!!!!!
ron
marckostac,
The problem is shrinkage not expansion. The long, edge glued planks making the main portion of the tables tops were made from "outdoor" wood and then was brought into an indoor office. Typically an air conditioned office would much less humid than than the outdoors thus, shrinkage across the grain. Wood does not typically shrink much lengthwise with the grain. So I am assuming the end cap was screwed to the plank top at the ends as well as the middle so as the plank top tried to shrink towards the middle from both side it is prevented from doing so thus the splitting.
There seems to have been a significant humidity change and it is possible that the wood could have split and cracked without the end caps but i doubt they would have been as sever
The 100 year old wood was plenty dry..as others have stated the tables were made improperly. More pics of the underside of the table would be nice...
How do you know that it was dry?.just because it is 100 years old, it doesn't mean poop
unless it was stored in a heated enviroment, it is still only going to be air dryed. if it was stored in a barn it is still going to air dried and like I said previously , if you stick it into an a/c environment-toast
ron
Got to agree with Sid on moisture content. A granary (which is a barn to us southeners) has both wood outer exposed directly to rain and the inside is exposed to humidity with both unfinised. As I see it a combination of mistakes on this job. Improper drying.. no gradual acclimation to the new area it will be moved too... capping the ends not allowing for expansion.. wet wood (probably) glued and screwed to a base whiich won't allow expansion and the fact you have used 4 various species all with different expansion rates which does not help the obvious major mistakes already committed.
Not sure who did the work and they might be great outside constructions guys but.. they are without a clue as to making furniture that is going to end up inside in air conditioned and heated enviroments. If you realy want to save the project.. you are going to have to tear it apart.. rip.. let it dry properly.. acclimate and then make allowances for expansion and contraction on the inside controlled climate. The various varieties could be used IMO but not under the circumstances they were used.
Good luck...
I think you've already got your answers. The environment the barn wood was is was undoubtedly damper than the (air-conditioned?) office. The wood was not well-enough seasoned and conditioned to it's final environment. The frame was proably also a mistake, though not the biggest factor. Though I've not used (or heard of) Swamp White Oak, I don't buy the statement that it "always cracks".
I can understand the cracks, but the wood should not have split along the glue lines. That usually means that not enough glue was used, the wrong type of glue was used, or the joint was not clamped well enough or long enough. A properly glued joint should fail adjacent to the glue line, not along it. When I glue up a tabletop and trim the ends square, I end up with a 1/4"-ish strip. I try to break each section at the glue line. In the attached photo, the break at left is along the glueline - not good. The break at right is a good sign - it runs adjacent to the glueline.
To prevent further cracking, the wood should be moved to a less-dry environment (but not outdoors). Once the wood has dried/settled/reached equillibrium, the cracks can either be sawn out then the table glued back together, left alone, filled, or reinforced with splines/butterfly keys.
It seems that you've already received a pretty clear answer to what went wrong, so I don't need to add anything. What remains to be done is to "harvest the lumber" again, this time from the storeroom, and have a craftsman use it to build tables from scratch.
The damage is clearly due to a lack of knowledge on the part of whoever made the tables. Perhaps well-intentioned, naive, I can't know...but that's another issue. Get someone who knows what they are doing to re-make the tables.
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