# Trim curiosity question



## Duane Bledsoe (Oct 18, 2012)

On the backside of trim I buy at Lowe's there is a routed out channel the full length of the sticks. Why is that there? Does it serve a purpose? I'm assuming it's for stress relief in the wood to help keep it laying flat.


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## tcleve4911 (Dec 16, 2006)

It's to help create a tight connection where the egde of the trim contacts the wall covering and the jamb.
If it were flat with no recess, the wall and the jamb would have to be perfectly on plane and they are usually not.


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## Leo G (Oct 16, 2006)

Has a few functions. It removes stock and makes it lighter, for shipping. It makes it easier to install on surfaces that are uneven and it provides a balancing relief to help keep the molding flat over time.


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## Tman1 (Jan 14, 2013)

That channel minimizes contact with the wall to the edges. All the imperfections in the wall will force the molding to stick out in various places if it has a perfectly flat back. By having the channel, it is only affected by the imperfections at the edge of the molding. Many of these the molding will just flex around and you won't even see them. But, if the molding had to flex around an imperfection in the middle, then there would be a gap at the edge.


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## WarnerConstInc. (Nov 25, 2008)

It was never really about wall in differences, it originated from how it ran through a moulder and to reduce shipping weight.


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## Leo G (Oct 16, 2006)

Which is why I mentioned it first. It was first done with flooring.


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## Duane Bledsoe (Oct 18, 2012)

You know, I wondered if it might have had something to do with shipping weight. I tried to see a higher purpose in it, too, but I'm not surprised to learn it has its roots in saving a buck like so much else does. Can't blame them though. It's sort of brilliant. Remove stock in an area that won't be missed and make money in its absence. I bet they even repurpose the left over sawdust.


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## mics_54 (Oct 28, 2008)

I know the real reason...but it's a secret.

OK it isn't a secret.

...has nothing to do with shipping...end user always pays that anyway....the added tooling and setup wouldn't be worth the savings.

...has nothing to do with the machinery.

it has everything to do with controlling cupping without the need to worry about grain orientation. ....same if its flooring, siding or cedar decking.

The back kerf is wider on some crown and base mouldings to make installs easier on non flat surfaces....althought it makes it more difficult when drywall has a gap at the floor.


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