The Forestry Forum

I am making some 1x6's 10' long into roof decking. I am wondering how much play there should be vertically between the tongue and the groove. So in the below photo I want to get an idea of how much gap to put at the surfaces labeled 'top' and 'bot'. Or should they be totally snug.

(https://forestryforum.com/gallery/albums/userpics/21063/tng.jpg)

I am using a Freud 99-036 adjustable tongue and groove router bit set. I was originally going to run the router on top of the work piece but the instructions say to use the bit on a stationary router table. So the ability to keep the work piece perfectly flat against the table during a run is also a concern.

You will be frustrated when assembling or laying the decking if you don't leave some room for debris and some wood movement. How much will depend on how much movement you get and how frustrated you don't want to be when laying it down. ;)
Ease the corners of the tongue as well so the two pieces slide together easily, one into the other.
Make some practice runs.

Have you thought about shiplap, its a tad more forgiving on assembly. 
http://en.wikipedia.org/wiki/Shiplap (http://en.wikipedia.org/wiki/Shiplap)

My old man used this on his new house instead of OSB for sheathing on outside of house and for the subfloor in the second level.

I think I will stick with t&g. Without anything more definitive I will adjust the tongue smaller to leave 0.5mm at both 'bot' and 'top'. The other idea is to run the wood through twice with hopefully the 2nd pass being a bit more precise to listen for and fix any areas where the work piece was not all the way down or all the way back. The bits are such that the tongue always fits snug against the back of the groove and there is no way to change that so just a little sawdust could prevent the pieces totally sliding together:

http://www.freudtools.com/index.php/products/product/99-036 (http://www.freudtools.com/index.php/products/product/99-036)

Canopy
Are you using the bit in a hand held router or on a table router? If on a table router, you can adjust your fence to limit the depth of cut when routing the tongue which would leave a gap in the groove for saw dust or imperfections on either side.
Rusty

I just make them fairly snug but so they slide together easily.
Shiplap is easier IMO and just as good for roof deck.

Yeah I think shiplap is a lot easier to install and is a LOT more forgiving
(https://forestryforum.com/gallery/albums/userpics/35211/DSC06295.JPG)
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