Replies

1. 
   rob_ss | Jun 21, 2021 02:18am | #1

   A bit depends on where you are.
   .03" per inch across the grain would be a good rule of thumb, so movement would be 0.33 to 0.66 inch.
   You could construct the hole so that it got smaller in wet weather, but if you did, the whole thing would probably tear itself apart over time.

2. 
   EdWeber | Jun 21, 2021 10:14am | #2

   It does depend on where you live, the MC of the wood at time of construction and grain orientation (rift sawn, flat sawn, etc)
   For a width of 37" I would leave at least 3/8" per side, possible 1/2" but that's just me. There's no penalty for allowing extra room for movement.
   If you want to get technical, The wood database says,
   Redwood Shrinkage: Radial: 2.4%, Tangential: 4.7%, Volumetric: 6.9%, T/R Ratio: 2.0

3. 
   RalphV | Jun 21, 2021 12:16pm | #3

   Thanks Rob and Ed. But my question was whether the hole only expands as humidity increases or whether the swelling of the wood could also cause the hole to shrink. I've already checked expansion rates.

4. 
   user-7624188 | Jun 21, 2021 02:58pm | #4

   If you are building the door now, in the summer, it is very likely that the wood will shrink come winter time. I recommend reading two FW articles by Christian Becksvoort and Gerald Curry on wood movement, both titled 'Understanding Wood Movement'. Curry's article is a summary of wood science that will definitely answer your question.

5. 
   gulfstar | Jun 21, 2021 04:11pm | #5

   The hole will get larger as the wood takes moisture. Althrough it is true that wood expands in all directions it will expand to make the door larger and away from the centre pieces above and below the window. It could only contract if it were in a rigid frame where when expanding it could only go towards the centre.

6. 
   DRBWWing | Jun 21, 2021 05:32pm | #6

   Its just the movement across the width of the boards. Is the wood really getting that wet?

   In that application outdoors I would play it safe and allow for 1/4" per foot, 3/4" across the whole door.

7. 
   RalphV | Jun 21, 2021 05:57pm | #7

   Thanks Gulfstar and others. Commonsense would tell me that if the door is swelling, the hole would have to swell not shrink. Not much different than a the glass panel in a french door. But then common sense has gotten me into trouble before.

8. 
   user_7675709 | Jun 21, 2021 06:46pm | #8

   When it comes to expansion/contraction remember that the piece you cut out to make the hole, if subjected to the same conditions as the rest of the door, will always fit into the hole it came out of. The only caveat is the end grain will absorb and release moisture faster than the face grain of the panel.

   It sounds like the door will be spectacular.

9. 
   hoovermd | Jun 21, 2021 10:58pm | #9

   Just want to mention that you should think about the wood movement WRT your finish choices too.

   I have some 8' tall x 32" wide interior walnut doors. The door frames are walnut also.

   They were all finished with 100% pure Tung Oil. Nothing added but a 50% citrus solvent for the first 4 or 5 coats. I did a coat per day for a week, wiping after each. A coat every other month for a year and then annual after that for about 5 years. So far so good, no?

   However now about 10 years out suddenly the frames (and some of the doors) are suddenly sticky to the touch! Seems that the movement of the wood over the years is now pushing the oil out of the wood. I never would have imagined that 5+ year old Tung would find its way out of the wood, but it has!

   I've started using some odorlees mineral spirits and 3M white pads on the finish. It really shines up and removes the stickiness to some degree but not completely.