Architrave Moulding

[DavidC]

Hi Guys

I want to know why a rebate channel is cut on underside of most architraves

I have just received some 75 x 16mm WRC that has been milled square cut and no rebate underside. I will be fixing on exterior of house against weatherboard and window frame. Will this matter that no rebates ?

[OBBob]

Hey ... try this link.

http://www.woodworkforums.ubeaut.com...ad.php?t=25417

[Sigidi]

David,

did you get your answer from the provided link?

Basically when you have a DAR board, it will react to moisture evenly/predictably, when one face is machined in the case of architrave/ moulding/door sills etc. The machining increases the surface are of that face of the board - meaning it will absorb more moisture in a given situation that it's flat face, this will produce a cup in the board.

To counteract this, manufacturers machine the rear face to even up the surface area to reduce the likelihood of the boord cupping due to variances in moisture uptake/loss due to surface are differences.