It looks like some further information on this subject would be useful, so I started a new topic so hopefully the search engine can find it in the future.

Hardwood lumber isn't as easy to purchase as common softwood framing lumber. With softwoods, you trot down to your local home center and whatever they have, that's what you get. With hardwoods, you can have more control, but you have to know what to ask for. I haven't had to do this for more than a few years, and so spent some time on the web to see what has changed. Not much, really, other than there is a wealth of information easily obtainable now. Let's look at some of the considerations.

There are three items that must be specified to accurately describe what you want, assuming you've already decided what species you're purchasing; these are GRADE, SEASONING, and SURFACE. They are not related to each other, but all of them affect the outcome of your project.

GRADE is a standard description of the physical characteristics of a board. Lumber grading is not administered by the government; there is no USDA Prime lumber, but rather by a manufacturers association for the purpose of having standard product descriptions so lumber can be purchased sight unseen. Native American hardwood grades are administered by the National Hardwood Lumber Association, NHLA. There is no requirement for lumber to be graded for sale, but mills grade lumber to be competitive in the market place.

The concept used in grading hardwood lumber is the percentage of useable material that will be obtained from a given board when cut into pieces of a specified size, called "cuttings". Unfortunately, none of the cuttings are as large as a car sill, so unless you have a vendor that allows you to "pick the pile", there is no guarantee that all the material you buy will be usable for the largest pieces. However, because of the nature of lumber, stock with few defects will also tends to have small defects, so the higher the grade, the better the chance that the stock will only contain small appearance defects that won't matter in structural applications, but one must be aware that there is no guarantee that all the pieces will be useable. Lumber has to be purchased with the thought in mind that some pieces will have defects that require them to be cut for smaller pieces, and extra stock has to be figured into the order.

The traditional finest grade was called FIRST, or FIRSTS as a plural, followed by SECONDS. These now are sold as one grade, FIRSTS and SECONDS, or FAS. Next best is SELECT, often combined with FAS and called SELECT and BETTER, SEL & BTR, or SAB. These are then followd by #1 COMMON, #2 COMMON (now split into 2A & 2B grades) and #3 COMMON (also now split into 3A & 3B) #3B COM is the stuff that pallets are made of.. There is also an appearance grade called FIRST ONE FACE (F1F) that guarantees the appearance of FAS on only one side, with no defects on the other worse than #1COM.on the other. This is good for interior panels, etc, but not for sash, doors, or structure.

The NHLA web site has a really good page illustrating these grades, prepared by the American Hardwood Export Council. View it at:

http://www.natlhardwood.org/illustrated_guide/IllustratedGradingGuide.pdf?userid=

SEASONING refers to the drying of lumber. Live wood is mostly water. Even after the free water has left the cells, it is still appx. 30% water bound in the cell structure. Lumber used in outdoor structures will eventually dry to about 15% moisture content, and the loss of this water is what causes shrinkage and warping. There are two ways to reduce the moisture content in lumber; air drying and kiln drying.

To effectively control wood movement in its final use, lumber has to be dried to a slightly lower moisture content than it will see in the final application; typically 12% for outdoor structural work. The lumber will then slowly absorb moisture until it comes into equilibrium with its environment, and will remain stable through seasonal changes thereafter. Air drying in a the proper environment can yield lumber with a 12% MC, and this is perfectly adequate for car restoration structural work. Contrary to popular belief, kiln drying doesn't produce better lumber, only drier lumber. Lumber to be worked into interior millwork, or fabricated in a heated shop, needs to be dried to appx. 8% MC, and this low figure is not possible with air drying alone. However, kiln dried lumber that has been stored outdoors or in a damp environment will absorb moisture until it comes in to equilibrium with that environment, and so will be no different than air dried lumber, except it will cost more.

Kiln drying is also the faster way to bring lumber to market, as the old rule of thumb for air drying is one year per inch of thickness, but this has its risks. It is easy to ruin lumber with an improper kiln schedule. Here are some defects to be aware of:

CHECKS Splits that start at the end of a board caused by the end drying and shrinking more rapidly than the middle. these typically run further into the board than they appear to. Also possible with air drying if the board ends weren't sealed.

SURFACE CHECKS The surface of the board dries so rapidly that it splits, then the splits close up as the interior of the board catches up. These may not be an appearance problem. but do decrease the structural properties.

CASE HARDENING A slightly slower kiln schedule keeps the surface from checking, but the wood at the surface hardens up, then is put under compression as the interior of the board shrinks, leaving un-relieved stresses. These stresses can cause strange dimensional behavior later when the board is cut. These are the boards that look like a pair of pants legs when they come off the saw blade when being ripped in half.

HONEYCOMB The absolute worst kiln defect, rendering perfectly good lumber fit only for stove wood. An aggressive kiln schedule forces the wood to shrink so quickly that it literally tears itself apart. The checks close up on the surface of the board, but when cross cut the entire interior is a series of oval shaped voids. Receiving a load of KD lumber like this is grounds to refusing the shipment, but it is difficult to spot, especially on rough sawn lumber.

SURFACE is the finished milled on the boards. Hardwoods can be purchased ROUGH SAWN, surfaced one side (S1S), surfaced two sides (S2S), or surfaced four sides (S4S). Seems simple enough. However, some things to keep in mind: If you order 2" Rough and specify 1 7/8" S2S, the surfaces won't clean up completely. If you order 1 7/8" S2S when you really need 2" stock thinking that you will save money by only paying for 2" rough, you are probably paying for 2 1/2" stock anyway, and could just as well have ordered 2" S2S. You need to be clear what you need and what you will be doing with it. Talk to the lumber dealer and seek his advice. I also ran into an interesting web site with a question and answer board that has several people from the USDA Forest Service Forest Products Labatory as technical advisors. view the forums at:

http://www.woodweb.com/SiteMap.html

As I said earlier, GRADE, SEASONING, and SURFACE are not particularly related to each other. You can buy a given grade either unseasoned, air dried, or kiln dried, and you can buy it either rough or surfaced. The main limitation is typically what products have sufficient demand that mills cut them, and lumber dealers and wholesalers stock them. Hopefully the information above will help in the search for restoration materials.

A company as a source of hard woods, they advertise 35 speices in stock, and do custom milling and welcome small lot orders from one board to a several truck loads:

http://www.yukonlumber.com

I've never done business with them, but they have an excellent reputation.

Good summary Dennis. A few other points. Hardwood lumber is commonly sold in random lengths and widths so if these are available at a dealer, picking through a pile can save you money. Odering exact length, width, and thickness can cost a lot more since you essentially are buying the trim anyway. That may be less of an issue if you are buying a large lot of stock, as the mill may be more likely to accomodate any custom needs.

Thickness of hardwoods is sold and gauged in 'quarters' measured on the rough sawn stock. A common size is 5/4 (five quarters) which is one and one quarter inch thick rough, yielding about 1 and 1/16 when surfaced two sides (S2S).

Some species are very difficult to find in thicker ranges, like white oak, one of the woods that is particulary appropriate to rail car restorations. White oak has a very closed cell structure which is one of the reasons it is so resistant to rot and water damage. The water just cannot penetrate and if you keep the surface protected and painted, it will last decades.

But this exact trait makes it very difficult to dry after being harvested from the log. The interior moisture takes a very long time to escape. If it is forced by a kiln, the resulting checks, splits and other defects result in a dramatic lowering of good material, driving up the price based on the yield of good lumber. If you air dry, the one year per inch may not yield the final moisture content you want. As the clock ticks away the cost of this inventory at a mill or lumber yard, waiting to be sold later, represents a significant investment in capital, so it also drives up the cost.

So, if you see a project coming down the line in 5 or 10 years, it would be smart to get the fresh white oak yourself, stack and sticker it, seal the ends, protect it from the weather, buy extra to allow for developing defects, and wait it out.

Bob Kutella

Dennis and Bob:

Thanks for the info.

Les