Using tongue and groove on external door

[garethharvey]

I am looking to use some Western Red Cedar as tongue and groove on the bottom half of a door. The door is 800mm wide, any suggestions how loose should I fit them to allow for expansion?

 

[sunnybob]

Is this just decorative? or is it going to part of the strength of the door?

 

[ColeyS1]

If you allow 1mm per 100mm of board you won't go far wrong- that's assuming the woods not sopping wet and freshly cut down. The key to the doors survival is securing each board to allow for movement. A single fixing in each width of the board will ensure the spacings remain equal, even if the gaps aren't.
Embarrassing example -

Bottom rail failed but it was the lack of any fixing at all in the boards that led to the huge gap. That was green oak amd because no board was fixed it allowed the tongues to pop out in the heat.When the damp arrived they expanded and couldn't relocate so had explosive rail lengthening results.

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[garethharvey]

Is this just decorative? or is it going to part of the strength of the door?

Just decorative.

 

[garethharvey]

If you allow 1mm per 100mm of board you won't go far wrong- that's assuming the woods not sopping wet and freshly cut down. The key to the doors survival is securing each board to allow for movement. A single fixing in each width of the board will ensure the spacings remain equal, even if the gaps aren't.

Thanks, I was thinking 1mm was not enough, the timber is kind dried so possibly at it’s smallest.

 

[ColeyS1]

If you allow 1mm per 100mm of board you won't go far wrong- that's assuming the woods not sopping wet and freshly cut down. The key to the doors survival is securing each board to allow for movement. A single fixing in each width of the board will ensure the spacings remain equal, even if the gaps aren't.

Thanks, I was thinking 1mm was not enough, the timber is kind dried so possibly at it’s smallest.

That was assuming it's properly wedged mortise and tenon. If it's unwedged it really won't hurt to go more. Securing each board is key. I've got a pic somewhere of a door that bowed about half inch where the boards expanded so much. It was only the strength in the wedged tenon that held it all together. Goes without saying, give everything atleast 1 lick of finish before assembling- tongues, grooves, rebates etc [WINKING FACE]

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