Expansion and Contraction..Am I thinking correctly

  • Advertise with us

« back to Woodworking Skill Share forum

Forum topic by CharlesNeil posted 02-09-2017 06:30 PM 4639 views 0 times favorited 63 replies Add to Favorites Watch
View CharlesNeil's profile


2501 posts in 5116 days

02-09-2017 06:30 PM

I am doing 3 board Walnut counter tops for my daughters kitchen.. ( interior decorator and her call) . I have to do a 90 corner, mitered. I want to glue the seam solid, I say it will be ok.. Your thoughts … She wants this seam tight and sealed. tops are 25 ” wide ( 3 boards). I feel confident, but not 100% sure.

63 replies so far

View pintodeluxe's profile


6489 posts in 4058 days

#1 posted 02-09-2017 06:33 PM

I feel like if it has room to expand at both the front and back it will be okay. Is there a backsplash planned that could hide an expansion gap at the back?

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View a1Jim's profile


118258 posts in 4822 days

#2 posted 02-09-2017 06:37 PM

How about doing sliding dovetails mitered corners ?


View Dez's profile


1176 posts in 5322 days

#3 posted 02-09-2017 06:39 PM

It should be just fine as long as it can freely expand and contract. I usually fasten mine at the back and allow the front to move.

-- Folly ever comes cloaked in opportunity!

View CharlesNeil's profile


2501 posts in 5116 days

#4 posted 02-09-2017 06:44 PM

The question is , being mitered will they move together .. they should but!!!!!

View a1Jim's profile


118258 posts in 4822 days

#5 posted 02-09-2017 06:51 PM

As you know they will move across the grain how much probably will be determined by the width of the mitered
part of the countertop. it seems like I’ve seen you miter table tops with mitered edges 4 or 5” without concerns ? I guess another issue is if your using 1/4 sawn material or not ?


View 000's profile


2859 posts in 2144 days

#6 posted 02-09-2017 06:53 PM

Just my thinking!
As they expand they will hit in the front so the pressure would want to open the miter in the back.
I don’t know if they will expand enough to do that though. Controlled environment and acclimated wood, it may be OK.

Think to yourself, what would you tell someone if they were asking you?
Pretty much, that’s probably the right answer.
Myself, if it were for me, I would probably do it.
For a client, might not want the liabilty to HAVE to re-do it, and then how do you re-do it any better?

View CharlesNeil's profile


2501 posts in 5116 days

#7 posted 02-09-2017 06:54 PM

Jim, this is all flat sawn walnut… draw an “L” with a miter, the question is, its it or is it not going to move in unison ..

View CharlesNeil's profile


2501 posts in 5116 days

#8 posted 02-09-2017 07:00 PM


I totally agree, I have never done this, I do furniture, but to glue it seems logical, but then again, ?

Im going to domino it, glue it solid , and see what happens, if it has issues, Ill certainly hear about it and would make a new top..and so will you folks, one of those , live and learn things.
The wood is well acclimated and dry, I will finish it top/ bottom and seal it well. Time will tell,

View a1Jim's profile


118258 posts in 4822 days

#9 posted 02-09-2017 07:02 PM

If you putting you miter were two counters meet at a miter I would guess the will move in a similar manner but still would have concerns about it affecting the miter .would crystal allow a board at the miter were you could do a stop dovetail allowing both sides of the “L” to move at whatever each side wants to do?


View Rich's profile (online now)


7461 posts in 1835 days

#10 posted 02-09-2017 07:03 PM

Have you already purchased the lumber? If not, go for quarter sawn. It will be more stable.

Edit: Sorry, I just saw your post about flat sawn. As Roseanne Roseannadanna used to say, never mind.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View RBWoodworker's profile


442 posts in 4597 days

#11 posted 02-09-2017 07:30 PM

yes, they’re going to move since they are solid wood.. no doubt.. I think it all depends on the moisture content of the boards and if some are as dry as the others.. if it were me, I woukd miter them, route for a spline to go the width of the miter, but stopping anot inch or so from the edge.. and use those “T” bolts to draw the joint tight and use no glue.. the spline and T bolts should keep the seam tight and with no glue, allow for movement..

-- Randall Child

View papadan's profile


3584 posts in 4614 days

#12 posted 02-09-2017 08:07 PM

Build your counter top and seal it with bar top sealer, there will be no movement.

View jerryminer's profile


962 posts in 2687 days

#13 posted 02-09-2017 08:48 PM

The critical thing here, IMHO is that with wood movement, the miter angle will change—so the attachment system needs to allow at least one leg to “swing” to accommodate.

Countertop bolts will keep the miter tight, but movement still needs to be accommodated.

-- Jerry, making sawdust professionally since 1976

View TheTurtleCarpenter's profile


1053 posts in 2311 days

#14 posted 02-09-2017 09:03 PM

. My thought Charles would be to use two 1/8 splines thru the mitres or 1 at 1/4” width using a slot cutter in a router. I would fit and glue the mitre at the shop if I could using a template from the wall to fit and also be sure to seal all ends, edges and bottom to cut down on taking on moisture.

-- "Tying shoelaces was way harder than learning to Whistle"

View Kazooman's profile


1540 posts in 3197 days

#15 posted 02-09-2017 09:33 PM

I’ve certainly never done this, but I think it may be a problem. As either piece expands along its considerable width the portion at the miter is bearing against the end grain of the other piece. I don’t see how it can move freely without opening up the joint at the rear. On the other hand, if the pieces are contracting they would pull away from each other and just open up the entire joint unless the entire top is allowed to float freely.

On second thought, I think that it might work as long as the entire top is allowed to move. We normally don’t worry about expansion with the grain, but here the cross grain expansion of one piece will be transferred along the length of the other. Allowing the top to move lengthwise and not just across the grain might be critical.

I think I need to go build a mock up and dump some water on it.

showing 1 through 15 of 63 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics