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KemoSabe
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Getting back to the subject of miters, there's a reason why half lap and mortise & tenon joinery were invented.

There's also a reason that raised panels are supposed to be able to "float" in the stiles and rails.

Wood moves. It has since the dawn of woodworking. Mitered corners are going to show the effects of the movement more than a square butted half lap or a M&T joint.

Even a mitered mortice and tenon joint will show movement under moderate changes in moisture content. Exterior is going to be tough to control, if not entirely impossible.

As for composite, thermal expansion alone will force the miters open at the long point.
 
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loneframer said:
Getting back to the subject of miters, there's a reason why half lap and mortise & tenon joinery were invented. There's also a reason that raised panels are supposed to be able to "float" in the stiles and rails. Wood moves. It has since the dawn of woodworking. Mitered corners are going to show the effects of the movement more than a square butted half lap or a M&T joint. Even a mitered mortice and tenon joint will show movement under moderate changes in moisture content. Exterior is going to be tough to control, if not entirely impossible. As for composite, thermal expansion alone will force the miters open at the long point.
So at this point the best way to handle this is to educate your customer in writing and at the kitchen table. If you wait until the miters open to tell them, they may think your BS them to get out of the fix. Communication is key to this business.
 

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Artist and not a curator
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Getting back to the subject of miters, there's a reason why half lap and mortise & tenon joinery were invented.

There's also a reason that raised panels are supposed to be able to "float" in the stiles and rails.

Wood moves. It has since the dawn of woodworking. Mitered corners are going to show the effects of the movement more than a square butted half lap or a M&T joint.

Even a mitered mortice and tenon joint will show movement under moderate changes in moisture content. Exterior is going to be tough to control, if not entirely impossible.

As for composite, thermal expansion alone will force the miters open at the long point.
It can be done and is very tricky with ipe. I've got one over a couple seasons that the miter hasn't busted loose. Screw placement, joint prep, and then adhesion technique all play big into it. When I have a customer who wants an unmoving miter on one of my decks I make sure they understand in the beginning how much MORE it will cost, it took me a long time to figure out how to do it, just like bending ipe... That $h!t ain't cheap.
 

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Discussion Starter · #124 ·
Californiadecks said:
So at this point the best way to handle this is to educate your customer in writing and at the kitchen table. If you wait until the miters open to tell them, they may think your BS them to get out of the fix. Communication is key to this business.
Agreed, one more lesson learned the hard way. I guess I've been very fortunate with my miters up to this point. I've been running my stair pattern that way for quite some time now without any hiccups. I'm changing my approach to the mitered boarder (celebrated) and most importantly, contract wording. (with explicit detail of the realities of wood. )
It so happens that my New Years Resolution is to communicate better .
 

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Xtrememtnbiker said:
So if you were doing a picture frame capstock and you wanted to miter the corners... would you leave an intentional gap to match the rest of your gaps?
That depends on the temps outside. If it's 105 degrees I make them tight, if its cold I sometimes just run a saw kerf up all of them, it keeps it looking consistent and shows that it was intentional. Sometimes there's a post in the way to prevent this. When this happens the post takes up most of the joint and it's not that important.
 

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KemoSabe
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It can be done and is very tricky with ipe. I've got one over a couple seasons that the miter hasn't busted loose. Screw placement, joint prep, and then adhesion technique all play big into it. When I have a customer who wants an unmoving miter on one of my decks I make sure they understand in the beginning how much MORE it will cost, it took me a long time to figure out how to do it, just like bending ipe... That $h!t ain't cheap.
That might make it in FLA, but I doubt it would here. We see single digits with very low humidity in the winter and triple digits in the summer with 100% humidity. We get times where it rains for several days straight and times where it doesn't rain for weeks on end.

I've never seen a mitered joint in wood of any kind stay put for more than a full cycle of seasons around here.

I built an Ipe deck several years back that was gapped with 3/16 spacers that you can stick a piece of 1/2" plywood in on the southern exposure. On the northern exposure, maybe 1/16 to light 1/8 overall shrinkage in board width.

A half lapped miter glued and pegged would probably not resist the forces trying to open up those miters.
 
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