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I checked several pieces of wood tonight for moisture content and they were all 9% - 11%. This is in my new garage shop and the wood has been there all summer. We have had a much wetter year than average, at least one 45 day period where it rained (no lie, not kidding) EVERY SINGLE DAY for six weeks straight. This shop also has no insulation, is not heated or cooled with the house beyond a window AC unit or gas heater. It is a brick house, and the garage shop is fully bricked on all exterior walls, and shares one wall with the house that is not bricked. The house has no insulation either. There were several days this past summet when the atmosphere inside the shop felt like outside, from heat and humidity.

In my old basement shop, wood always stayed very dry at 5%-7%. Now I am worrying that this increase in average moisture will have a noticeable effect on my projects. Should I be concerned? I have only lived here six months. Don't know what winter will bring. I currently have no plans to insulate or upgrade the heating and cooling. I just want to know if you all think I can get by as is and not have severe changes in what I am used to in woodworking in these new conditions.
 

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Duane,

The humidity should go down this winter. There is a big difference between a basement and an insulated space at ground level. Remember, the ground maintains a fairly constant temperature year round and as long as there is no water problems (infiltration), with good ventilation, then the humidity probably remained fairly constant and lower then the outside. Different story with the garage. Fluctuations in temperatures and exposure to outside humidity are the problem.

9-11% is really not that excessive for wood. Sorry, but that is probably the reality for your part of the country. Try living along the Gulf Coast from Texas to Florida. I'd be grateful for those kinds of figures.

I guess I'd have to ask what the average humidity level inside the house is normally. I understand your concern, however, be realistic. If you are building "fine furniture" and are worried about severe shrinkage once it moves to a permanent home with a lower moisture level, then do what some folks do...take the wood and store it in the house so it acclimates before you use it. This way if you are shooting for that mystical ideal percentage there won't be a drastic change when it is finished and inside for good.
 
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Relative humidity where I live hovers around 60% year-round. I don't have a moisture meter, so I don't know what the moisture level in my wood is, but I'll bet it's higher than yours. But the relative humidity in my home hovers around 40-50%, so it's not a problem as long as the items I build go in my house. It's the humidity swings that kill you. I did build one item that went in a very large commercial building. I know the humidity gets real low in the winter there because of the static electricity from walking on the carpet. I did have some problems with wood shrinkage on that piece, but I had broken all the rules and made no provisions whatever for movement in the design.

Here's my thoughts:
1. The wood needs to be thoroughly dry (kiln dried) before you bring it home. If not, It can take years for it to dry out sufficiently in your shop.
2. The wood needs a few days to acclimate to the humidity levels in your shop before you make the final cuts.
3. Take the time and effort to design for wood movement so it won't destroy your piece when it does happen. Remember that wood moves about twice as much in the tangential (along the circumference of the growth ring) direction as the radial (across the growth rings) direction, and it practically doesn't move at all along the length of the board (end grain to end grain). Various woods have different rates of shrinkage, but a good rule of thumb is to allow for 1/8 inch of movement for every 12 inches of cross-grain width.

Instead of worrying over the things that are hard to control, like the humidity levels in your shop, spend your time on the things that are easier to control, like the design of your piece.
 

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Pretty much all the work I do is on wood with a 10-15% MC. I seal it pronto and even thinned stock joints hold tight.
 

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Most woodworkers hope for a working range of +/- 10*. If you sell professionally you have no way of knowing where your work will wind up so you build so that the wood can move where it needs to.

The inside of a house should be between 30 and 70% R humidity. At 30 you start getting dry mouth and eyes and headaches. At 70 and more you risk mould. Your workshop should be closer to 30 I would think as there are no moisture sources except you when you are in it. It still is a matter of building to allow movement no matter.
 
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I made a dining room table for my son in Albuquerque,NM that was 1 1/4"X40"X96" a few years ago. The clear VG pine material I used was Kiln Dried,I didn't
test the moisture level here in Seattle when I made it. About 3 months after I delivered it and set it up,he called and "Guess What Dad?' It had split length wise down the middle. All of the pine beams and lintels in his house were cracked and split,and he said the table matches now.LOL
Herb
 

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I live in Tennessee and have a garage shop with AC and a dehumidifer. I will empty the dehumidifer twice a day. I am just saying that garages get a lot of humidity in them.
 

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Discussion Starter #11 (Edited)
My problem is I don't really know how to design for wood movement. In panels, I can do it with deeper channels and rubber inserts, stain before assembly, and all that, because the panels aren't glue joined inside the frame. But in just assembling a frame for a table or cabinet, making shelving, fishing rod racks, benches, or wherever the joinery is firmly fastened with nails, screws, glue or adhesive, and in tight joints such as tongue in groove, mortise and tenon, or even just butt joints, I have no idea how to plan for movement.
 

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The key is to design and build to allow wood to move without restriction through its width. So, as an example, a frame can be put together without worrying about wood movement. However when you add a top you must allow the top to move independently of the frame. This can be done by screwing the top onto the frame through slots that will allow the top to move. There are also clips available that fit into slots in the frame. If you understand frame and panel which you obviously do then apply the same thought process to all your other work. Hope this helps.
 

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Discussion Starter #13 (Edited)
Well, let me run this by you all and see what you think. I have had success building a bookshelf using solid but cheap 1x12's where they intersected perpendicularly to form the sides, shelves, and top, and I nailed them all solid, first by adding a 1x2 strip across the width of the upright side boards to support each shelf. The shelves themselves formed a ladder frame once I nailed them in, and I used glue also. Then I added a face frame all around, that butts right up to the shelf edges tightly, and also added a top made of edge glued boards (since it had to be wider than 1x12), also firmly nailed. Everything is nailed solid. I left it raw and unfinished, never sealed, and it has been over a year and yet nothing ever split or warped. Seems to me this is in defiance of wood movement rules (right?). So I learned nothing about wood movement from that, and that is one place where I would have expected the most problems. I guess I can see expansion room across the width of the shelves and upright sides, and top, unrestricted other than by the 1x2 supports, since their grain orientation is perpendicular to all the grains of the boards they're nailed to.

Also, it seems pocket hole screw joinery would cause problems since they would restrict movement also. Of course, they work, so there must be something I don't understand.
 

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My problem is I don't really know how to design for wood movement. In panels, I can do it with deeper channels and rubber inserts, stain before assembly, and all that, because the panels aren't glue joined inside the frame. But in just assembling a frame for a table or cabinet, making shelving, fishing rod racks, benches, or wherever the joinery is firmly fastened with nails, screws, glue or adhesive, and in tight joints such as tongue in groove, mortise and tenon, or even just butt joints, I have no idea how to plan for movement.
The big problem with wood movement occurs when you have a wide piece (or several narrow pieces glued together to make a wide piece) constrained from expanding and contracting with changing humidity levels by being rigidly attached to something that doesn't expand or contract in similar fashion. This can happen if you fasten a wood tabletop firmly to a steel base so it can't expand and contract across the grain. Or, it could happen with a wooden base because the wood doesn't move along its length, only its width and thickness. So in either case, you'd need to fasten the top to the base with slotted holes, or some other method that allows for a little side-to-side movement. You know how we don't like the end grain of the wood to show on a nice tabletop? So we put a narrow piece across the end to make a nice "breadboard" end. But if you glue the breadboard continuously across the width of the table, the tabletop will probably split when it dries because the breadboard won't let it shrink. So, breadboards are usually tongue and grooved to the table end, but only fastened at the middle, or if the ends of the tongue and groove are fastened at all, with a pin in a slot.

You generally don't have to worry about movement in pieces less than about 3 inches wide. You can even glue two 3 inch pieces cross-grain to each other. Wood glue allows enough creep to accommodate that small amount of movement. But with wider pieces, the total amount of movement at the edges is too much for the glue (or other rigid fastening method) to stand and something has to give. You don't have to design for movement in your mortise-and-tenon joints and other joints involving narrow frame members, just the wide pieces.

The other place wood movement has bitten me is in gluing up wide panels. I once glued up a 48 inch wide panel, carefully matching the grain to make the joints invisible. Trouble is, I had the smiles (growth rings) on the board ends all turned the same way. When a board moves, it tends to straighten the growth rings a little. All my boards moved the same way so my 48 inch panel bowed like a barrel. If I had alternated the smiles on the board ends, the panel may have been a little wavy, but the waves would have cancelled each other out instead of adding to each other.

The wood-movement snake is bound to bite you sooner or later. But it's not fatal, and you'll be a better woodworker after than before. I highly recommend the book, UNDERSTANDING WOOD by Bruce Hoadley.

http://www.amazon.com/Understanding...1443398081&sr=1-1&keywords=understanding+wood
 

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Well, let me run this by you all and see what you think. I have had success building a bookshelf using solid but cheap 1x12's where they intersected perpendicularly to form the sides, shelves, and top, and I nailed them all solid, first by adding a 1x2 strip across the width of the upright side boards to support each shelf. The shelves themselves formed a ladder frame once I nailed them in, and I used glue also. Then I added a face frame all around, that butts right up to the shelf edges tightly, and also added a top made of edge glued boards (since it had to be wider than 1x12), also firmly nailed. Everything is nailed solid. I left it raw and unfinished, never sealed, and it has been over a year and yet nothing ever split or warped. Seems to me this is in defiance of wood movement rules (right?). So I learned nothing about wood movement from that, and that is one place where I would have expected the most problems. I guess I can see expansion room across the width of the shelves and upright sides, and top, unrestricted other than by the 1x2 supports, since their grain orientation is perpendicular to all the grains of the boards they're nailed to.

Also, it seems pocket hole screw joinery would cause problems since they would restrict movement also. Of course, they work, so there must be something I don't understand.
Unless I have it pictured wrong in my mind, the only place in your bookcase where you have wide boards constrained across their width is where the shelf supports are attached to the sides. In all other places the book case is free to get wider or narrower as required by changing moisture levels. I'm guessing you may have been saved by fairly constant humidity levels. Also, the "cheap" wood you used may have been a species that doesn't move as much as others.
 

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Duane another consideration is the space heater you bought for the Garage/Shop. since it is an unvented gas heater, the combustion gases will be water and CO2. this will add water vapor to your shop in the form of raised humidity. And you will have to replace the combustion air with outside air, which means that you will have to crack a door /window to let in some new moist air so the CO2 levels don't get too high. You will probably see the widows steam up when you start the heater if it is colder on the outside than inside. Higher humidity is not good for your tools or your wood.
Just something to ponder.
Herb
 

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You might consider sliding dovetails, I've had real good luck using them on wall shelves. Nearly half my customers live at or within a mile from the ocean the rest within 3 miles. The Cape is the 3rd muggiest place I know, Great Lakes #2 and Fort Myers #1.
 

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My problem is I don't really know how to design for wood movement. In panels, I can do it with deeper channels and rubber inserts, stain before assembly, and all that, because the panels aren't glue joined inside the frame. But in just assembling a frame for a table or cabinet, making shelving, fishing rod racks, benches, or wherever the joinery is firmly fastened with nails, screws, glue or adhesive, and in tight joints such as tongue in groove, mortise and tenon, or even just butt joints, I have no idea how to plan for movement.
You started by describing your weather, which clues me in that you are not close to me. Here in the Pacific Northwest, our average dry days is only average 56 days a year without rain. Out of those remaining 56 days, that does not include foggy or overcast. (I live close to the Olympic Rain Forrest.) Much of the time, our humidity is between 90-98%. On the same day, we get humidity fluctuations of over 25%. But until 3 weeks ago, this year we had one of the driest dry-seasons in history.

As a general rule, if you are making fine furnishings, you want to match your tooling and assembly environment to what your furnishings home will end up as. But that is in a perfect world and is not always feasible. So instead, acclimate gradually.

Best practice scenario, become familiar with spline joints. If joining large cross-grain to long-grain, try to plan for expansion. But if the design does not allow for that, watch the hardness of you joiniing adhesives and what your finish you use.

One note here-- once a furnishing is "home" inside a house, it's environment is fairly stable. People like to be comfortable. Large sudden changes are not comfortable.

If your finish breaths, use a pliable joining adhesive. A finish that breaths is going to have more expansion and contraction as humidity changes, than a finish that is sealed and allows no moisture to get in or out. There is a reason why old heirlooms used hide glues, besides the technology of the era.

Saying that, in today's age of "super adhesives," if you look at where a joint fails, on a hard, non-pliable adhesive, the failure, most of the time, is outside the adhesion, in the surrounding material.

A tip taught to me, is if you fit a joint for joining... join it (assembly) that same day.If not, plan for, and allow for things not being as tight or fine a fit.
 
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