Attaching Tongue and Groove back to rabbeted book case

[John Stan]

Hi -
Easy question. I just can't seem to find a definitive answer. The back to my book case is tongue and groove boards 5 inches wide by 1/2 inch thick. They will be placed in rabbets. What is the nailing pattern for attaching the boards to the back of the book case? Is it one nail across the top and bottom of the board (2 nails per board)? This approach is suggested in this months Popular Woodworking. Or is it two nails across the top and bottom of each board (4 nails per board). I have seen this approach in many places as well. Most recently in this months Fine wood working.

Thanks in advance for your help.
-John

[Sean Hughto]

The idea of tongue and groove is to allow the boards to move - expand and contract. You therefore want to fasten with movement in mind. I do not believe there is a definitive attachment pattern because multiple variables play into it: width, species, grain, required durability of the back, etc. A single nail in the middle of each board may be enough. On a cabinet I did where I expected items might sometimes impact or push from the inside, I used screws. In short keep the movement in mind and think it through for the piece at hand.

[James Scheffler]

I would use four nails per board. The nails allow for some movement, so I think the individual boards will be fine from that perspective. I think the most important thing is to leave a little gap between each board.

Jim S.

[Rich Purdum]

IHMO, you want to allow the individual pieces of the back to move independently, thus you want one fastener in the middle of each, top and bottom. You'll also want to take into account current moisture content when you decide how tightly to fit them. The FWW bookcase author used screws not nails but not sure how important this is. I'd probably go with screws.

[Tony Shea]

Why couldn't you nail each board twice, top and bottom, inside each toungue. Therefore you would allow for wood movement in one direction as well as hide the fastener. This is typically how toungue and groove paneling, floor, etc is installed in homes. One would think that the same techniques could be used for the cabinet backs.

[Jeff Schmidt]

What Tony describes has been my practice, though one nail in another location would work similarly. Bear in mind that the intent of the tongue and groove is for all of the expansion and contraction to be compensated for by the internal space between the tongue and the bottom of the groove with the boards butted up tight one-to another.

[glenn bradley]

I use 1 at the top and 1 at the bottom for 3" boards. I will defer to others on 5" boards.

[Frank Drew]

Like Sean, I like screws; they're more work, but there's less chance of splitting the wood (predrill, of course), they're better looking if anyone happens to look, and, if there's any problem with the back, screws come out much, much easier than nails.

5" boards are wide enough to worry about cupping, so instead of fastening in the middle, I'd use one screw top and one bottom at the board edge with the groove, maybe 3/4" or an inch in from the edge. That should restrain cupping of both boards (the groove holding down the other board by its tongue), but still allow seasonal movement.

Easy enough to go back and add more fasteners if those prove insufficient.

I'd fasten half lap the same way, putting the nail or screw on the edge with the overlap.