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Decking mitre gaps

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Chrisryzen1

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Hi there, we’ve just installed new decking and oiled it. But for some reason the inside of the mitred joints have spread open. About 2-3mm gap tapered to nothing. Would I be able to use wood filler in the gap then oil it again. Or would it look obvious that there was a gap there. The boards are 120mm wide so the joint is probably roughly 140mm long. Many thanks
 

sammy.se

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Hi, and welcome to the forum.

I don't think filling will provide you with a permanent solution - it's likely that over the next couple of seasons the filler will crack and fall out, due to the reasons below:

Wood will expand and contract, and change shape with moisture levels. Wood outdoors is even more susceptible to this than wood indoors (where changes in moisture and temperature are less extreme).

Mitres are notorious for opening up - in fact there are seasoned woodworkers on here that avoid them as much as possible.

Could this be something you learn to live with, as part of the natural characteristics of the wood?
2mm-3mm isn't so bad in the context of decking - some other members on here might have some suggestions on how to remedy this

Regards,
Sammy
 

RichardG

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You could run a saw down the mitre and make the gap parallel so it looks like you installed in that way?

Richard
 

AJB Temple

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Richard's idea above is a good one. It is pointless trying to install and keep tight mitres on decking. Better to accept there will be gaps and make a feature of it.
 

Racers

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As the boards dry and shrink the angle changes. My decking has the same problem but I am not going to do anything about it it's not worth wouring about.
It will help the boards to dry out.

Pete
 

Chrispy

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Now we have had a bit of rain nip out and have a look and see how your mitres are now.
 
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